/) 10. 3 '//I / U. S. DEPARTMENT OF AGR OFFICE OF EXPERIMENT STATIONS BULLE A. C. TRUE, Director EXPERIMENTS ON THE EFFECT OF MUSCULAR WORK UPON THE DIGESTIBILITY OF FOOD AND THE METABOLISM OF NITROGEN. CONDUCTED AT THE UNIVERSITY OF TENNESSEE, 1899-K )( )< >. By CI IAS. E. WAIT, Ph. TX, F. C. S., Professor of Chemistry at the University of T. tmeh^e. WASHINGTON: GOVERN M E N T PRINTING OFFIC E 1 9 2 . OFFICE OF EXPERIMENT STATIONS. A. C. True, Ph. D., Director. E. W. Allen, Ph. D., Assistant Director and Editor of Experiment Station Record. C. F. Lang worthy, Ph. D., Editor and Expert on Foods and Animal Production. NUTRITION INVESTIGATIONS, MIDDLETOWN, CONN. W. O. Atwater, Ph. D., Chief of Nutrition Investigations. C. D. Woods, B. S., Special Agent at Orono, Me. F. G. Benedict, Ph. D., Physiological Chemist. R. D. Milner, Ph. B., Editorial Assistant. 2 i R OF TRANSMITTAL U. s. Department of Agrioultube, Office of Experiment Stations, Washington, D. 0., July 5, 1902. Sir: I have the honor to transmit herewith a report on experiments on the effect of muscular work upon the digestibility of food and the metabolism of nitrogen eondueted at the University of Tennessee in 1899 and 1900 by Charles E. Wait, professor of chemistry, under the immediate supervision of Prof. W. O. Atwater, chief of nutrition inves- tigations. These studies form a part of the nutrition investigations, conducted under the auspices of this Office, to gather information regarding the food habits in different regions, the comparative values of different foods, the laws of nutrition, and related topics. In making these investigations Professor Wait was assisted by Messrs. C. O. Hill, W '. K. Hunter, C. A. Mooers, and C. G. Schenk, of the department of chemistry of the University of Tennessee. The present investigations supplement earlier work at the same institution on the effect of muscu- lar work on digestion and metabolism, questions which are of great importance, and concerning which there is little information available. It is believed that the present investigation is a valuable contribution to the subject. The report is therefore submitted with the recommendation that it be published as Bulletin No. 117 of this Office. Respectfully. A. C. True, Director. Hon. James Wilson, Secretary of AgricuLtun . CONTENTS. Page. Introduction 7 Preparation, sampling, and analysis of food materials.. 8 Composition of food materials and feces 9 Details of the experiments carried on in 1899-1900 11 Experiment No. 17 11 Experiment No. 18 14 Experiment No. 19 17 Experiment No. 20 20 Experiment No. 21 23 Experiment No. 22 ! 26 Experiment No. 23 29 Experiment No. 24 32 Experiment No. 25 35 Summary of coefficients of digestibility 38 Metal >olism of nitrogen . . . .• 39 ( '< miposite samples 40 5 fSCULAR WORK AND ITS EFFECT UPON DIGES- TION AND METABOLISM INTRODUCTION. With a view to learning something of the food requirements when muscular work Is performed and of the digestibility of the diet and the income and outgo of nitrogen under conditions of varying muscu- lar work,- experiments have been carried on for several years at the University of Tennessee. The effect of muscular work upon the metabolism of nitrogen has been often studied in the past, as has also the question of diet when different amounts of muscular work are performed. Many of the previous nutrition investigations conducted under the auspices of this Department have had to do with these problems/' It appears that comparatively few experiments with man have been made to determine the influence of muscular work upon the digestion of food. The results of the earlier experiments on this subject at the Univer- sity of Tennessee have been reported in previous publications of this Office. 6 The present bulletin reports the results of nine additional experiments (Nos. 17-25, inclusive) conducted in 1900, which w r ere divided into three sets of three experiments each. With one excep- tion, each of the experiments covered twelve consecutive days, being divided into three periods of four days each. In every case muscular work was performed during the second period, while in the first and third periods as little muscular work was performed as possible. In the first series of experiments (Nos. 17-19) the diet furnished a normal amount of protein and energy, and was the same in all three periods. In the second series (experiments Nos. 20-22) the diet in the first and third, or rest periods, furnished several grams less nitrogen and 500-600 calories less energy than a normal diet. During the sec- ond or work period the nitrogen content of the ration was unchanged, while the energy value was increased some 500 or 600 calories. In other words, the energy was brought up to the normal. In the third series of experiments (Nos. 23-25) the diet was uniform throughout the experiment, and in both rest and work periods furnished less protein and less energy than a normal diet. " U. 8. Dept. Agr., Office of Experiment Stations Buls. 75, 89, 98, and 109. ft U. S. Dept. Agr., Office of Experiment Stations Buls. 53 and 89. 7 8 The subjects of the experiments were the same three healthy young men with whom the earlier tests had been made. The food consisted of such articles as gelatin, milk, oatmeal, potato chips, rice, coffee, butter, eggs, and sugar, combined in such a way as to form a simple mixed diet of reasonable palatability. The diet was somewhat simpler than in the experiments previouly reported. The digestibility of the ration was determined by the usual meth- ods, which have been described in earlier publications of this Office. '' The food and feces were analyzed, the latter being separated by means of charcoal taken in gelatin capsules. The income and outgo of nitrogen was also studied. In addition to determining the total amount of urine and its nitrogen content, deter- minations were made of the amount and proportions of nitrogen in the urine corresponding tc eight-hour periods during the second or work periods, as it was believed that any effects of muscular work on the excretion of nitrogen might be thus more readily observed. Similar determinations were made during the third period to learn whether the muscular work produced effects which were noticeable after the work had ceased. In most of the experiments these determinations were also made for purposes of comparison in the first rest period. The external muscular work consisted in walking up and down a hill 140 feet high on a smooth path. The amount of muscular work which can be measured in such cases is the product of the body weight of the subject, the number of feet which his body is vertically raised each trip, and the number of trips, that is. weight multiplied by num- ber of trips uphill multiplied by 140 feet equals foot-pounds of work. So far as is known, the energy expended for the motion of forward progression has never been satisfactorily measured with man. The amount of work performed by a man walking downhill is also unknown. It is certain, therefore, that more work was performed by the subject than is shown by the method of calculation followed. While it is to be regretted that the total amount of work could not be accurately measured, the results are sufficient for the purposes of the experiments, since the object was to require of the subject an amount of muscular work sufficient to produce fatigue and to compare the results with different subjects under the experimental conditions. So far as an extended review of the literature shows, the factors which were not measured in these experiments have not been taken into account in simi- lar experiments reported by other investigators. PREPARATION. SAMPLING. AND ANALYSIS OF FOOD MATERIALS. As stated above, the diet followed in these experiments was simple and made up of a comparatively small number of articles. The foods r. S. Dent A-r.. oilier of Experiment Stations Buls. 53 and 89. h V. s. Pept. A.srr.. Office of Experiment Stations Buls. 21 and B5. 9 chosen were of such ;i nature that it is believed little difficulty would be experienced in obtaining a comparatively Large supply of practi- cally uniform composition, a matter of considerable importance in experiments in which it is desired to have a diet furnishing uniform amounts of nutrients and energy. The milk, butter, coffee, sugar, rice, and eggs were the usual products. The bread was made from patent wheat flour and was the so-called Vienna loaf. The gelatin was one of the ordinary commercial products, as was also the rolled oats used. The potato chips were prepared by frying very thin slices of potato in deep fat until light brown, (are was taken to secure repre- sentative samples of all food materials for analysis. The milk was purchased fresh each day, an aliquot portion taken as a sample, and these portions united to form a eomposite sample for the whole period. The oatmeal was sampled before cooking. In the case of bread, rep- resentative slices from each loaf served as samples. COMPOSITION OF FOOD MATERIALS AND FECES. The composition of the foods and feces was determined by the analytical methods adopted by the Association of Official Agricultural Chemists." with such modifications as have been suggested by Atwater and Woods/' and with minor variations which experience in this labora- tory has shown to be desirable. The heats of combustion of the samples of food materials and excre- tory products were not determined in these experiments. The values for energy given in the tables of the different experiments were cal- culated. The energy of the food materials was calculated from the total nutrients of the diet by the factors 5.65 calories per gram of protein. 9.40 calories per gram of fat, and 4.15 calories per gram of carbohydrates.' The energy of the feces for the rest and work experi- ments was calculated from the total organic matters of the feces by T use of the average heat of combustion per gram of feces in the rest and work experiments of 1897-1899, viz/ 7 5.19 calories per gram in the rest experiments and bA'2 calories per gram in the work experiments. The energy of the urine was computed by assuming that for every gram of protein in the digested material there would be 1.25 calories of energy lost in the organic matter of the urine/ 'Fable 1 shows the composition of the food materials and Table 2 the composition of the water-free feces. The proportion of nitrogen in the food materials and feces is included in the tables, as well as the "U. S. Dept. Agr., Division of Chemistry Bui. 46, revised. ^Connecticut (Storrs) Station Report, 1891, p. 47, and U. 8. Dept. Agr., Office of Experiment Stations Bui. 21. 'Connecticut (Storrs) Station Report, 1899, p. 104. ,f V. S. Dept. Agr., Office of Experiment Stations Bui. 89, p. 15. e V. S. Dept. Agr., Office of Experiment Stations Bui. 53, p. 28. 10 protein which represents the total nitrogen multiplied by the factor 6.25. It is recognized that the use of this factor involves more or less error, especially in the ease of cereals; but as it has been more gener- ally used than any other factor in computing the results of digestion experiments it has been retained. Should it seem desirable at any time to recalculate the results, making use of other factors, this can be readily done from the statistics published in this report. Table 1. — Composition of food material*. Labora- tory num- ber. Food materials. Water. Nitrogen. Protein (NX6.25). Fat. Carbohy- drates. Ash. 449 Per cent. 73.67 11.69 8.27 11.05 85.88 86.26 86.30 86.18 86.23 85.96 86.51 86. 42 85.98 1.00 6.94 8.25 8.62 32.49 31.81 31.81 4.88 3.73 3.01 Per cent. 2.08 .22 .24 .30 .59 .55 .57 .58 .56 .56 .55 .54 .54 .75 2.27 2.45 1.33 1.52 1.51 1.59 .78 1.20 1.25 Per cent. 13.00 1.39 1.56 1.89 3.69 3.44 3.56 3.63 3.50 3.50 3.44 3.38 3.38 4.69 14.19 15.31 8.31 9.51 9.42 9.94 4.88 7.50 7.81 Per cent. 11.17 83.86 87.43 84.79 4.61 4.54 4.46 4.72 4.94 4.94 4.65 4.65 5.02 .36 7.01 7.18 .41 1.17 1.25 1.27 30.78 36.68 33.34 l'i r end. Per cent. 0.99 486 Butter 3.06 508 .do... 2.74 528 do . 2.27 481 Milk 5.10 5.02 4.86 4.67 4.85 4.85 4.63 4.82 4.83 93.82 69.99 67.39 82. 16 55. 96 56.55 55.92 56.37 47.80 51.05 100.00 .72 494 do .74 499 ...do... .82 504 do .80 515 do . . . .75 520 ...do .75 525 do .77 535 ..do... .73 540 do .79 480 .13 482 1.87 505 ...do.. 1.87 485 Rice .50 484 .87 507 do .97 527 ...do 1.06 483 3.09 506 do 4.29 526 ...do 4.79 Coffee .. Table 2. — Composition of water-free substance of feces. Labora- tory num- ber. 490 491 492 495 496 497 500 501 502 511 512 513 516 517 518 521 522 523 531 532 533 536 537 538 541 542 543 Sample. Feces . ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. ....do. Nitrogen. Protein (NX6.25). Fat. Carbohy- drates*. Per cent. Per cent. Per cent. Per cent. 4.77 29.83 15. 72 29.05 4.98 31.13 25.53 23.78 4.69 29.32 24.24 26.73 4.98 31.13 14.60 29.11 4.96 31.02 25.69 23.41 4.44 27.77 30.50 21.65 4.92 30.78 13.51 29.16 5.10 31.89 23. 98 23. 03 4.83 30.22 23.97 25. 40 4.76 29. 76 22.91 19.29 5.00 31.24 30.38 15.30 4.71 29.40 31.99 16.93 4.88 30. 48 22.53 21.98 4.87 30.44 33.23 14.18 4.59 28.67 36.13 15.67 5.00 31.27 19.66 22.43 4.93 30.80 29. 23 16.58 4.82 30.14 25. 49 22.03 4.91 30. 71 18.38 23.81 5.09 31.80 18.64 26.76 4.85 30.33 16.57 28.91 4.93 30.84 20.07 22.66 5.12 32.01 27. 55 18.99 5. 02 31.35 28. 13 18.03 4.86 30.39 21.77 20.59 5.20 32.49 27.13 19.43 4.87 30.41 34.03 14.55 Per cent. 25.40 19.56 19.71 25.16 19.88 20.08 26.55 21.10 20.41 28.04 23. 08 21.68 25.01 22.15 19.53 26.64 23.39 22.34 27.10 22. 80 24.19 26.43 21.45 22. 49 27.25 20.95 21.01 11 DETAILS OF THE EXPERIMENTS CARRIED ON IN 1899 1900. The experiments recorded in the present report were conducted in the winter of L899 L900, and were so arranged that each experiment wa> carried on with the three different subjects simultaneously. 'The sup- per preceding each experiment consisted largely of bread and milk, and the experimental period in every case commenced with breakfast. With this meal the lampblack used to color the feces and to permit a separation of portions pertaining to the diet under investigation was taken. In the earlier investigations the experiment proper was pic- ceded by a period in which the diet was adjusted SO that the subject was in nitrogen equilibrium. This plan was not followed in the pres- ent investigation, as (judging by the experience then gained) it was not necessaiy. EXPERIMENT NO. 17. This experiment was carried on with a chemist 30 years of age, in good health. The experiment was divided into three periods of four days each. During the second period the subject made 74 trips up and down hill. This was calculated as equivalent to 1,617,122 foot- pounds or 55,S76kilogrammeters of work. The mechanical equivalent of one calorie is, in round numbers, 8.100 foot-pounds. The heat equivalent for the work measured for the four days was, therefore, 130 calories, or 82 calories per day. As previously stated, the actual work performed must have been considerably more than the amount thus estimated. Subject. — Chemist, 30 years of age. Weight i without clothing ). — At the beginning of the experiment 68.6 kilograms (151 pounds); at the end of the first period 68.2 kilograms (150 pounds). During the remainder of the experiment the weight remained unchanged. Duration. — Tin- experiment began with breakfast, December 9; the second period with breakfast. December 13, and the third period with breakfast. December 17. Each period, therefore, occupied four days. 12 Table 3. — Results of experiment No. 17. Labor- atory num- ber. Pood materials. Weighl of ma- terial. Total organic matter. Nitro- gen. Protein. Fat Carbohy- drates. Ash. Heat of com- bustion calcu- lated. 149 First Period (Rest). Digt Mi an < xperiment NO. 206. drum*. 364 120 8,000 100 320 120 1,200 40 320 800 drum*. 88 103 1,072 99 291 109 800 37 320 2 Grams. l.lu .26 47. 20 .7:. 7.26 1.60 18. 2 4 .31 lira ins. 47 2 295 5 i:» 10 111 2 drums. 41 101 369 Grams. drums. 1 1 58 Calories. 186 Butter . 481 Milk 408 94 221 99 672 23 320 480 Gelatin 482 22 6 1 10 1 485 Rice 484 Bread 11 12 483 Potato chips Coffee .32 2 Total . . 2,921 83.51 522 559 1,840 84 15,839 Feces (water-free). 490 147 7,020 110 7.01 70. 25 44 23 43 37 571 597 Amount digested . Coefficients of di- gestibility (per 2,811^ 96.2 76.50 91.6 478 91.6 536 95.9 1,797 97.7 47 56.0 14,671 92. 6 Second Period (Work). Digestion experinu nt No. 207. 449 364 120 8,000 100 320 120 1,200 40 320 800 88 103 1.040 99 291 109 800 37 320 2 7.57 .26 44.00 .75 7.26 1.60 IS. 24 .31 47 2 275 5 45 10 114 2 41 101 363 A 4 59 486 Butter. 494 Milk 402 94 224 99 672 23 320 480 Gelatin ... 482 Oatmeal Rice Bread Potato chips Sugar Coffee Total 22 6 1 10 1 485 484 14 12 483 .32 2 2,889 80.31 502 553 1.834 85 15. 646 Feces (water-free). Urine Amount digested . Coefficients of di- gestibility (per cent) 495 140 5,837 105 6.97 71.68 -14 20 41 35 569 572 2,784 73.34 458 533 1,793 50 14,505 96.4 91.3 91.2 96.4 97.8 58.8 92.7 Third Period (Rest). Digestion experiment No. 208. 449 364 120 8,000 100 320 120 1.200 40 320 800 88 103 1,031 99 291 109 800 37 320 2 7.57 .26 45. 60 . 75 7.26 1.60 18.24 .31 47 2 285 5 45 10 114 2 41 101 357 4 4 66 486 Butter... 499 Milk Gelatin 389 94 224 99 672 23 320 480 482 Oatmeal Rice Bread 22 6 1 485 484 14 12 4S3 Potato chips Sugar Coffee .32 2 Total 2, 880 81.91 512 547 1.821 92 15, 592 Feces (water-free). Urine 500 130 7. 233 96 6.40 70. 4 a 40 18 38 34 498 590 Amount digested. Coefficients of di- gestibility (per cent) ..." 2, 784 75. 51 472 529 1,783 58 14,504 96.7 92. 2 92. 2 96.7 97.9 63.0 93.0 13 Throughout this experiment the urine was collected in portions cor- responding to eight-hour intervals. The results for the first period (rest) follow: Table 4. — Amount of nitrogen eliminated in theurme {digestion experiment No. .'06). Period. First day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen 8 a. in. 1 p. in. 12 p. in. to to to 1 I>. III. 12 p. in. 9 a. in. 550 710 602 6.05 6.82 5.42 1.10 1,112 .96 688 .90 417 6.34 6.26 4.63 .57 .91 1.11 508 683 357 5.54 6.76 4.68 1.09 .99 1.31 385 633 375 5.54 7.22 4.99 1.44 1.14 1.33 Total. 1 , 862 18.29 2, 217 17.23 1,548 16.98 1,393 17.75 The quantity of urine eliminated and its nitrogen content during the second or work period are shown in the following table: Table 5. — Amount of nitrogen eliminated in the urine {digestion experiment No. 201) . Period. First day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen 8 a.m. 4 p.m. to to 4 p.m. 12 p. m. 358 567 5.76 6.46 1.61 1.14 430 593 5.98 7.18 1.39 1.21 503 625 6.29 7.00 1.25 1.12 850 469 6.72 6.52 .79 1.39 12 p.m. to 8 a.m. 365 5.04 1.38 313 4.41 1.41 395 5.41 1.37 369 4.91 1.33 Total. 1,290 17. 26 1,336 17. o7 1,523 18.70 1,688 18. 15 14 During the third period, which was, like the first, a period of rest, the amount of urine eliminated and its nitrogen content were as follows: Table <>. -Amount of nitrogen eliminated in the urine {digestion experiment No. 208). 'eriod. 8 a. in. to i |». in. i p. in. to 12 j). m. .grams ..do.. .grams. . .do. .. First day: Weight of urine Weight of nitrogen Per cent of nitrogen second day: Weight of urine Weight of nitrogen Per rent of nitrogen Third day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen 667 6. II 1.13 635 ."». 52 .87 568 5. 68 1.00 653 5. SI 942 6. 78 .72 5 13 (i. 46 1.19 ;itmeal 22 6 1 9 4 485 Rice bread Potato chips 484 12 :\7 483 Coffee .16 1 Total 2, 732 74. 17 164 517 1,751 73 14, 749 Feces (water-free) Urine 491 121 4,981 97 6.03 52.02 37 31 29 24 503 Amount digested. Coefficients of di- gestibility (per 2, 635 68.14 427 486 1,722 49 13, 712 96.5 91.9 92.0 94.0 98.3 (17.1 93.0 Second Period (Work). Digestion experi- ment No. 210. 449 606 120 6,000 100 320 120 1,000 120 400 400 147 103 780 99 291 109 667 111 400 1 12.60 .26 33.00 .75 7.26 1. 60 15.20 .94 79 2 206 5 45 10 95 6 68 101 273 6 4 44 486 Butter 494 Milk 301 94 224 99 560 68 400 480 Gelatin 482 22 6 1 9 4 485 Rice... 484 Bread 12 37 483 Potato chips Coffee .16 1 Total 2,708 71.77 449 513 1,746 74 14, 605 Feces (water-free) 496 122 4,383 98 6.05 57.12 38 31 29 24 531 514 Amount digested. Coefficients of di- gestibility (per cent) 2,610 65. 72 411 482 1,717 50 13,560 96.4 91.6 91.5 94.0 98.3 67. 6 92. 9 Third Period |(Rest). Digestion experi- ment No. 211. 449 606 120 6,000 100 320 120 1,000 120 400 400 147 103 773 99 291 109 667 111 400 1 12.60 .26 34.20 .75 7.26 1.60 15.20 .94 79 2 214 5 45 10 95 6 68 101 268 6 4 49 486 Butter 499 Milk 291 94 224 99 560 68 400 480 Gelatin 482 Oatmeal 22 6 I 4 485 Rice 484 Bread . . 12 37 483 Potato chips Sugar Coffee .16 1 Total 2, 701 72. 97 457 508 1,736 79 14.561 Feces (water-free) Urine 501 123 5,068 97 6.27 56. 70 39 30 28 26 503 522 Amount digested. Coefficients of di- gestibility (per cent) 2, 604 66.70 418 478 1,708 53 13, 536 96 4 91.4 91.5 94.1 98.4 67.1 93.0 16 A> in the preceding experiment, the urine was collected in the three periods in portions corresponding to eight-hour intervals. The data for the urine in the first period follows: Table i>. — Amount of nitrogen eliminated in th urim (digestion < rperiment No. 209). Period. First day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine gra ms.. Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen 8 a. in. a p. in. 12 i>. m. to to to \ ]>. m. 12 p. in. 8 ]». in. Total. 530 4.24 5.81 .64 478 4.06 .85 325 4.23 1.30 562 4.66 .83 281 3.96 1.41 574 338 >.61 4.83 .96 1.43 270 1.125 3. 73 12.20 Li 220 1.690 3.23 13.70 1.47 1,019 11.95 260 3.93 1.51 1.147 3.83 14.17 1.63 The total amount of urine and its nitrogen content eliminated during the second or work period follows: Table 10. — Amount of nitrogen eliminated in tin- urine (digestion experiment No. 810). Period. 8 a. m. 4 p. m. First day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen : 510 5.46 1.07 545 5.67 1.04 532 5.91 1.11 575 6.15 1.07 4 p. m. 12 p. m. to to Total. 12 p. m. S a. m. 380 5.66 1.49 259 4.20 1.62 295 4.48 1.52 436 5.14 1.18 190 1,080 3. 14 14. 26 1.65 241 , 1.045 3.88 I 13.75 161 225 1,062 3.94 14.33 1.75 195 1,206 3. 49 14. 78 1.79 17 The third period like the first was a period of rest. The urine eliminated in periods corresponding to eight-hour interval-, and its nitrogen content, i*> shown in the following table: Table 11. — Amount of nitrogen eliminated in th urine (digestion experiment No. 911). Period. 12 p. m. I to Total. a. m. First day: Weight in" urine grams.. 503 Weighl of nitrogen <1<> — Per cent of nitrogen 1.13 Second day: Weight of urine grams.. 723 Weight of nitrogen do — 5.49 Percent of nitrogen .76 Third day: Weight of urine grain-.. .">!•"> Weight of nitrogen do 5. 4-") Per cent of nitrogen 1.00 Fourth day: Weight of urine grams.. 632 Weight of nitrogen do 5, Percent of nitrogen .90 1,3-51 11.71 lo.VI 1, 163 13.98 1,222 14.12 From the data recorded above the balance of income and outgo of nitrogen was determined. The results follow: Table 12. — Daily income and outgo of nitrogen in >\ pi rilin nt No. 18. Period. Nitrogen. In food. In feces. In urine. Gain. First period, rest Second period, work Third period, rest Days. Grams. 4 18.54 4 17.94 4 18.24 Gram*. 1.51 1 . 51 1.57 Grams. 13.01 14.28 14.18 Grams. 4.02 2.15 2. 49 EXPERIMENT NO. 19. This experiment was carried on with a student. C, age 22 years, and in good health. In the first and third periods as little muscular work was performed as possible. During the second period the subject made 80 trips up and down a hill. This was calculated to furnish 1,471.080 foot-pounds, or 50,992 kilogrammeters. equivalent to a total of 119 calories, or 30 calories per day. Subject. — Student ('. 22 years of age. Weight {without clothing). — At the beginning of the experiment, 63.0 kilograms (138£ pounds); at the close of the first period, 62.7 kilograms (138 pounds). During the second and third periods the weight remained unchanged. Duration. — The experiment began with breakfast December 9; the first period covered four days; the second began with breakfast December 13 and covered four days; the third began with breakfast December 17 and covered only three days. 1326— No. 117—02 2 18 Table Vd. — Results of experiment No. 19. Labora- tory num- ber. Food materials. Weighl of ma- terial. Total organic matter. Nitro- gen. Protein. Fat. Carbohy- drates. Ash. Heat of combus- tion calcu- lated. 449 First Period (REST;. Digestion expert meat No. tit. Grams. 519 120 6,000 100 320 120 1.200 160 400 400 Grams. 125 103 804 99 291 109 800 147 400 1 Grams. 10.80 .26 35. 40 .75 7.26 1.60 18.24 1.25 Grams. 67 2 221 5 45 10 114 8 (i nuns. 58 101 277 Qrams. Grams. 5 4 43 Calories. 486 Butter 481 Milk 306 94 224 99 672 90 400 480 Gelatin 182 22 6 - 1 10 5 485 Rice 484 Bread 14 49 483 Potato chips Coffee . . .16 1 Total 2,879 75.72 473 521 1.885 74 15. 392 Feces(water-free) 492 123 4,468 99 5.77 57. 16 36 30 33 24 514 546 Amount digested. Coefficients of di- gestibility (per cent) Second Period (WORKI. Digestion experi- m at No. US. Eggs Butter 2,780 69. 95 437 491 1,852 50 14,332 96.6 92. 4 92. 1 94.3 98.3 67.6 93.1 449 519 120 6,000 100 320 120 1.200 160 400 400 125 103 780 99 291 109 BOO 147 400 1 10.80 . 26 33.00 .75 7.26 1.60 18. 24 1.25 67 2 206 5 45 10 114 8 58 101 273 5 4 44 486 494 Milk 301 94 224 99 672 90 400 480 Gelatin 482 22 6 1 10 5 485 Rice 484 Bread 14 49 483 Potato chips Coffee .16 1 Total Feces ( water- free i Urine Amount digested. Coefficients of di- gestibility (per cent i 2, 855 73. 32 458 517 1,880 75 15, 2.50 497 123 4.040 99 5. 46 65. 75 34 38 27 25 537 530 2, 756 67.86 424 479 1,853 50 14.183 96. 5 92.6 92.6 92.7 98.6 66.7 93.0 Third Period (Resti. Digestion expt rt iiii nt No. 21U. 449 389 90 4.500 75 240 90 900 120 300 300 94 76 580 74 219 82 600 111 300 1 8.09 .20 25. 65 . 56 5. 45 1.20 13.68 .94 51 1 160 4 34 8 86 6 43 75 201 4 37 486 Butter 499 Milk 219 70 168 74 .504 68 300 480 Gelatin t82 17 4 185 Rice 484 Bread Potato chips Sugar 10 37 8 4 483 Coffee .12 1 Total 2.137 55. 89 351 383 1,403 60 11.405 Feces ( water-free ) Urine 502 84 4.245 07 4.06 .50.31 25 20 n 17 348 407 Amount digested. Coefficients of di- gestibility (per cent | 2. 070 51.83 326 363 1.381 43 10 650 96. 9 92. 7 92. 9 94.8 98.4 71.7 93 4 , 19 In all three periods of this experiment the urine was collected in portions corresponding to eight-hour periods, the amount and its nitrogen content being determined. Results from the first (rest) period follow: Table 14. — Amount of nitrogen eliminated in the urine [digestion experiment No. 212). Period. First day: Weight of urine grams.. Weight of nitrogen do — ivr cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of nrine grams.. Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do — Per cent of nitrogen 8 a. m. 4 p. m. 12 p. in. to to to 1 p. in. L2 i>. in. 8 a. m. 117 330 344 5. 16 6. 68 4.20 1 . 22 1.72 1.22 :>t:> :.:,7 246 6.10 4.01 8. 57 1.06 .72 1.45 275 333 203 4.10 5.56 3.19 1.49 1.67 1.57 368 500 300 5.48 6.40 3.42 1.53 1.28 1.14 Total. 1,121 L5.38 1,378 13.68 811 12. 85 1 , 158 15. 30 The amount of urine eliminated during- the second (work) period and its nitrogen content was as follows: Table 15. — Amount of nitrogen eliminated in the urine (digestion experiment No. 213). Period. Total. First day: Weight of urine gra ms. . Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen 20 The details of the elimination of nitrogen during the third (rest) period, which covered only three days, are given in the following table: Table lt>. — Amount of nitrogen eliminated in the urim [digestion experiment No. 214) • Period. 8 a. m. to 4 p. m. First day: Weighl of urine grams.. 382 Weight of nitrogen do 5.77 Per cent of nitrogen 1.51 Second day: Weight of urine grams. . 535 Weight of nitrogen do 5.89 Per cent of nitrogen 1.10 Third day: Weight of urine grams. . 4.50 Weight of nitrogen do 5.76 Per cent of nitrogen 1.28 4 p. m. to 12 p. m. 12 p. m. to 8 a. m. 6.51 443 6. 42 1.45 531 6.21 1.17 1.32 4.06 1.04 458 1.44 .97 Total. 1,438 17.53 1,368 16.37 1.439 16-41 The nitrogen balance was as follows: Table 17. — Daily income and outgo of nitrogen in experiment No. 19. Periods. Time. Days. First period, rest 4 Second period, work 4 Third period, rest 3 Nitrogen. In food. In feces. In urine. Gain. Grams. 18.93 18.33 18.63 Grains. Grams. 1.44 14.29 1.37 16.44 1.35 16.77 Grams. 3.20 .61 EXPERIMENT NO. 20. This experiment began a second set with the same subjects as in experiments Nos. IT, 18, and 19. In this set the diet in the first and third periods contained less than the normal amount of protein and energy, and during these periods little, if any, muscular work was performed. In the second period considerable muscular work was per- formed and the energy value of the diet was increased until it was equal in this respect to a normal diet. During the second period the subject of experiment No. '20 made the trip up and down hill fifty-two times. This, according to the method of calculation followed, gave 1,136,356 foot-pounds, or 49,4^1 kilogrammeters, equivalent to 92 calories, or 23 calories per day. Subject. — Chemist A, 30 years of age. Weight {without clothing). — At the beginning of the experiment 69.8 kilograms (153.5 pounds); at the end of the first period 6S.6 kilograms (151 pounds). During the second and third period the weight did not change. Duration.— The experiment began with breakfast March 8, the first period covered four days. The second period began with breakfast March 12. and covered four days. The third period began with breakfast March 16, and covered four days. 21 Table 18. — Results <<( < rperimeni No. 20. Labora- tory num- ber. Food materials. Weight of ma- terial. Total organic matter. Nitro- gen. Protein. Fat. Carbohy- drates. Ash. Heat of com bus- tion calcu- lated. 149 First Period ( K EST ) . Digestion experi- ment No. .'/•"'. Grams. 364 40 8,000 100 320 120 840 40 240 800 Grams. 88 36 1 , 042 99 288 109 565 37 240 2 Grams. 7.57 .10 if,, lo .75 7.H4 1.60 12.68 .48 Grams. 47 1 290 5 49 10 79 3 'nil ins. 41 35 378 a rams. Grams. i l 64 i ulories. 508 Butter 504 Milk 94 216 99 17.") 19 240 480 Gelatin 505 Oatmeal 23 6 1 8 2 186 Rice 507 Bread 11 15 506 Potato chips Sugar Coffee .32 2 Total 2,506 77.74 486 503 1,517 86 13, 769 Feces (water-free) Urine 511 128 6,705 92 6.09 71.90 38 29 25 36 477 560 Amount digested. 2,414 71.05 448 474 1,492 50 12 732 Coefficients of di- gestibility (per cent) 96.3 92.2 92.2 94.2 98.4 58.1 92.5 Second Period i Work). //.■;, .v'.-.-.v SXpen ni' nt No. J 16. Eggs 449 364 180 7,408 100 320 120 1,000 100 420 800 88 160 963 99 288 109 672 92 420 2 7.57 .43 41.48 .75 7.84 1.60 15.10 1.20 47 3 259 5 49 10 94 7 41 157 367 4 5 66 508 Butter 515 Milk 337 94 216 99 566 48 420 480 Gelatin 505 Oatmeal 23 6 10 4 485 Rice 507 Bread 12 37 506 Potato chips Sugar Coffee .32 2 Total 2,893 76.29 476 637 1,780 86 , 16, 063 Feces (water- free) Urine 516 130 3,858 98 6.34 66.99 40 29 29 32 531 545 Amount digested. 2,795 69.95 436 608 1,751 54 14, 987 Coefficients of di- gestibility (per cent) 96.6 91.7 91.6 95.5 98.4 62.8 93 3 Third Period (Rest). Digestion experi- ment No. 217. Eggs 449 364 40 8,000 100 320 120 840 40 240 800 88 36 1,063 99 288 109 565 37 240 2 7. 57 .10 44.80 .75 7.84 1.60 12.68 .48 47 1 280 5 49 10 79 3 41 35 395 4 1 60 508 Butter 520 Milk 388 94 216 99 475 19 240 480 Gelatin 505 Oatmeal 23 6 1 8 2 485 Rice 507 Bread 11 15 506 Potato chips Sugar Coffee .32 2 Total 2,527 76.14 476 520 1,531 82 13,981 Feces (water-free) Urine 521 130 6,971 95 6.50 69.80 41 25 29 35 493 544 Amount digested. 2,432 69.64 435 495 1,502 47 12, 894 Coefficients of di- gestibility (per cent) 96.2 91.5 91.4 95.2 98.1 57.3 92.6 22 In the second set of experiments the daily urine was collected in one portion during the first (work) period. On the first day of first period of experiment No. 20 the total urine whs L,890 grams and its nitrogen content 0.96 per cent, or 18.1 grams; on the second day 1,750 grams, with a nitrogen content of 1.02 per cent, or 17.9 grams; on the third day L,645 grams, with a nitrogen content of 1.13 per cent, or 18.6 grams; and on the fourth day 1.420 grams, with a nitrogen content of L.22 per cent, or L7.3 grams. The total nitrogen eliminated was there- fore 7.'). < -> grams. During the second (work) period the urine was collected in portions corresponding to eight-hour intervals. The results follow: Table 19. — Amount of nitrogen eliminated in tin urine (digestion experiment No. .W>). Period. 8 a. in. to 4 ]>. m. i p. in. to 12 p. rn. 12 ]>. in. to 8 a. in. Total. First day: Weight of urine .grains. . Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of nrine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen 345 5.00 1.45 305 4.70 1.54 282 5.16 1.83 358 G.19 1.73 5.48 1.81 353 7.17 2. 03 281 5. 99 2.13 350 5.99 1.71 :.. :;,s 1.60 245 4.70 1.92 295 :>. 4u 1.83 405 .">. 83 1.44 984 15. SO 903 it;. :.7 858 16.55 1,113 18.01 During the third (rest) period the urine was also collected in por- tions corresponding to eight-hour intervals. The amount of urine and its nitrogen content are shown in Table 20, which follows: Table 20. — Amount of nitrogen eliminated in the urine (digestion experiment Xo. 217). Period. First day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen ..do Per cent of nitrogen Fourth day: Weight of urine : grams. . Weight of nitrogen do Per cent of nitrogen 8 a.m. to 4 p.m. 448 5.82 1.30 725 6.53 770 6.62 397 5.56 1.40 4 p. m. to 12 p. m. 1,005 6.53 .65 613 6.26 1.02 , 645 794 12 p.m. to 8 a.m. 473 5.16 1.09 381 4.84 1.27 422 5.02 1.19 2.50 .84 Total. 1,926 17.51 1.719 17.62 1,837 18.03 1,489 16.64 28 From the data given in the preceding tables the balance of income and outgo of nitrogen whs calculated as follows: Table 21. — Daily income and outgo of nitrogen in experiment No. 20. Periods. First period, rest Second period, work Third period, rest . . . Time. Days. Nitrogen. In food. Grams. 19.43 19.07 19.04 In feces. Grams. 1.52 1.59 1.62 In urine. Grams. 17. 9* 16. 75 17.45 Gain ( + ) or 'in i, us. -0.07 + .73 - .03 EXPERIMENT NO. 21. The experimental conditions were the same as in the preceding experiment. The subject, a chemist, was 23 years of age and in good health. During the work period the subject made the trip up and down hill 68 times. This was calculated to yield 1,223,235 foot-pounds, or 42,422 kilogrammeters, equivalent to 99 calories, or 25 calories per day. The results of the digestion experiment follow: Subject. — Chemist B, 23 years of age. Weight (without clothing). — At the beginning of the experiment, 56.4 kilograms (124 pounds); at the end of the first period and the beginning of the second period, 55.9 kilograms (123 pounds); at the end of the second and the beginning of the third period, 56.4 kilograms (124 pounds) ; at the end of the experiment, 56.1 kilograms (123£ pounds). Duration. — The periods each covered four days and began with breakfast March 8, 12, and 16, respectively. 24 Table 22. — Result* of experiment No. Pi. Labora- nun,- Pood materials, ber. Weight Of nia- terial. Total organic matter. Nitr<>- gen. Protein. Fat. Carbohy- drates. A-h. Beats of combus- tion calcu- lated. 449 First Period (Bee Digestion experi- ment Xo. 218. drums. 608 40 6,000 100 320 120 640 120 320 400 Grams. 117 36 781 99 288 109 430 110 320 1 Grams. 12.65 .10 34.80 . 7"> 7.84 1.60 9.66 1.44 (i rum.--. 79 1 218 5 49 10 60 9 Grams. • 35 283 Grams. i 508 Butter 504 Milk 280 94 216 99 362 :.7 320 480 505 6 1 6 5 485 Rice... 507 Bread B 44 506 Potato chips Coffee . . . .16 1 Total . 2, 321 69.00 432 461 1,428 73 12 701 Feces (water-free) 512 115 4,497 88 5. 75 48.89 36 35 17 26 457 495 Amount digested. Coefficients of di- gestibilit\ (per cent) 2,233 63. 25 396 426 1.411 47 11.749 96.2 91.7 91.7 92.4 64.4 92.5 Second Period (Work). Digestion expt ri- ment Xo. 219. Eggs 449 608 180 5,408 100 320 120 800 180 500 400 147 160 703 99 288 109 537 166 500 1 12.65 .43 30. 28 .75 7.84 1.60 12.08 2.16 79 3 189 5 49 10 75 14 68 157 268 6 5 41 508 Butter... 515 Milk . 246 94 216 99 452 86 500 480 Gelatin 505 23 6 1 8 8 485 Rice 507 10 66 506 Potato chips Coffee .16 1 Total . 2,710 67.95 425 592 1,693 75 14,992 Feces (water-free) Urine 517 111 4. 061 87 5.41 54.90 34 37 16 25 472 4^y Amount digested. Coefficients of di- gestibility (per cent). ..." 2, 623 62.54 391 555 1,677 50 14. 031 96. S 92. 92.0 93.8 99.1 66. 7 93.6 Third Period (Rest). Digestion ex per i- m i lit Xn. 220. Eggs... 449 608 40 6,000 100 320 120 640 120 320 400 147 36 797 99 288 109 430 110 320 1 12.65 .10 33.60 .75 7.84 1.60 9.66 1.44 79 1 210 5 49 10 60 9 68 35 296 6 1 45 508 Butter 520 Milk 291 94 216 99 362 57 320 480 Gelatin 505 23 6 1 6 5 485 507 8 44 506 Potato chips Coffee .16 1 Total Feces (water-free) Urine Amount digested. Coefficients of di- gestibility (per cent) 2. 337 67.80 424 474 1.439 70 12,823 522 114 1,624 87 5. 62 54.65 35 33 19 ■j 7 452 486 2, 2.50 62. 18 389 441 1,420 43 11,885 96.3 91.7 91.7 93.0 98.7 61.4 92.7 On fche first day of the first (rest) period L,413 grams of urine was eliminated, containing <».7l> percent, <>r 10.2 grams nitrogen; on fche second day, L, 137 grams urine, containing L.03 per cent, or LI. 7 grams nitrogen; on the third day, 943 grams urine, with 1.3 per cent, or 1^.4 grama nitrogen; and on the fourth day, L,004 grams urine containing 1.4.') per cent, or L4.6 grams nitrogen. The total nitrogen eliminated w;i\ therefore, 48.9 grams, or L2.2 grams per day. During the second (work) period the urine was collected iii por- tions corresponding to eight-hour intervals and its nitrogen content determined. The details follow: Table 23. Amount of nitrogen eliminated in the urine (digestion experiment No. ?19). Period. First day: Weight of urine grams. . Weight of nitrogen do. Per eent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do. . . Per cent of nitrogen Third day: Weight of urine grams. Weight of nitrogen do... Per cent of nitrogen Fourth day: Weight of urine grams. Weight of nitrogen do. .. Per cent of nitrogen 8 a. m. 4 p. m. 12 p. in. to to to 1 p. m. 12 p. m. s a. in. 568 315 143 5. 15 4.85 2.76 .96 1.54 1.98 502 258 203 ."». 37 4.31 3.59 1.07 1.67 1.77 461 427 193 ... 1 1 5.64 :;. 15 1.18 1.32 1.79 155 323 213 5.78 4.55 3.71 1.27 1.41 1.71 Total. 1,026 13.1)6 963 L3.27 1,081 14.53 991 14.04 During the third (rest) period the urine was also collected in por- tions corresponding to eight-hour intervals. The results follow: Table 24. — Amount of nitrogen eliminated in the urine (digestion experiment No. 120). Period. a. m. to p. m. First day: Weight of urine grams..! 780 Weight of nitrogen do ' 6. 24 Per cent of nitrogen .80 Second day: Weight of urine grams. . 578 Weight of nitrogen do 6. 65 Per cent of nitrogen 1. 15 Third day: Weight of urine grams. . 655 Weight of nitrogen do 6. is Per eent of nitrogen .99 Fourth day: Weight of urine grams. . 51 13 Weight of nitrogen do 5. 28 Per cent of nitrogen 1.05 I p. m. 12 p. m. to to 12 p. m. 8a. m. 350 173 4.73 2.73 1.85 1.58 225 197 3.44 3.31 1.53 1.68 495 251 4.80 4.02 .97 1.60 280 137 1. 12 2.55 1.58 1.86 1 Total. 1,303 13.70 1,000 13.40 1.401 15.30 920 12. 25 26" The daily balance of income and outgo of nitrogen was calculated. The results are shown in the following table: Table 25. — Daily income and outgo of nitrogen in exjh riment No. 21. Periods. Time. Nitrogen. In food. In feces. In urine. Gain. First period, rest Second period, work Third period, rest .. Days. 4 4 4 drums. 17.25 16.99 16.95 Grams. 1.44 1.85 1.41 Grams. 12.22 13.73 13.66 Grams. 3.59 1.91 1.88 EXPERIMENT NO. 22. The experimental conditions were the same in this as in the two preceding experiments. The subject was the same as in experiment No. 19. During the first and third periods the subject performed as little external muscular work as possible. During the second period a considerable amount of external muscular work was performed. This consisted in making 70 trips up and down a hill 140 feet high. The work expended in raising the body to the height of the hill was calculated to 3 ield 1,319,799 foot-pounds, or 45,421 kilogrammeters. This is equivalent to a total of 106 calories, or an average of 24 calories per da}^. The details of the digestion experiment follow. Subject. — Student C, 22 years of age. Weiglrf (without clothing). — At the beginning of the experiment, 65.5 kilograms (144 pounds); at the end of the first period and the beginning of the second period, 64.3 kilograms (141.5 pounds); at the close of the second and the beginning of the third period, 65 kilograms (143 pounds); at the end of the experiment, 64.3 kilograms (141.5 pounds). Duration. — The experimental periods, each consisting of four days, began with breakfast on March 8, 12, and 16, respectively. Table 26. Results oj experiment No. ' ;. Labo- ratory Dum- ber. Pood materials. First Period t Ki>i Digestion > III' lit NO. itl. ISggti Weight of ma- terial. Total organic matter. Nitro- gen. Protein. drums. :•_' 1 218 5 (9 10 7'.t 12 lal. Carbon y ilriltrv Ash. 11. Hi of COmbllS- tion calcu- lated. •149 'hums. 666 lit 6,000 100 820 120 S40 L60 320 400 (trams. 134 36 781 99 268 109 665 147 320 1 d rums. 11.56 .10 34.80 .75 7.84 1.60 12.68 1.92 Grams. 62 35 283 Grams. Qrnms. 6 1 is 6 I 7 Calories. Butter 604 Milk 280 94 •jk; 99 175 76 320 INI Gelatin 605 ( latmeal 23 485 Rice 607 Bread 11 59 506 Potato chips Sugar Coffee .it; 1 Total 2,480 71.41 447 473 1,560 77 13,446 Feces | water-free 513 113 5,338 88 5. 32 56. 94 33 36 19 25 457 517 Amount digested. Coefficients of di- gestibility (per 2, 392 66.09 414 437 1,541 52 12, 472 96. 5 92.6 92. 6 92. I '.is. B t,7. :> 32 s Second Period (Work). Digestion expt ri- mnit No. ! 449 556 180 5, 408 100 320 120 1,000 220 .500 400 134 160 703 99 288 109 672 202 500 1 11.56 .43 30.28 .75 7.84 1.60 15.10 2.64 72 3 189 5 49 10 '.»! 16 (12 157 208 6 5 41 508 Butter 515 Milk 246 94 216 99 566 in:, 500 480 Gelatin . 505 23 6 1 10 9 485 Rice 507 Bread 12 81 506 Potato chips Sugar Coffee .16 1 Total 2,868 70.36 439 603 1,826 78 15,726 Feces (water-free) 518 114 4,146 92 5.23 62. 45 33 41 18 22 499 507 Amount digested. Coefficients of di- gestibility (per cent) 2, 776 65. 13 406 562 1,808 56 14, 720 96.8 92.6 92.5 93.2 99.0 71.8 Third Period (Rest). Digestion experi- ment No. ! 449 556 40 6,000 100 320 120 840 160 320 400 134 36 797 99 288 109 565 147 320 1 11.56 .10 33.60 . 75 7.84 1.60 12. 68 1.92 72 1 210 5 49 10 79 12 62 35 296 6 1 45 508 Butter 520 Milk 291 94 216 99 475 76 320 480 Gelatin 23 6 1 s 7 485 Rice 507 11 59 506 Potato chips Coffee .16 1 Total . . . 2,496 70.21 439 486 1,571 74 13,568 Feces (water-free) 523 107 5,996 83 5.16 62.09 32 27 24 24 431 509 Amount digested. Coefficients of di- gestibility (per cent) 2,413 65.05 407 459 1,547 50 12, 628 96.7 92.6 92.7 94.4 98.5 67.6 93.1 28 In t lie* first (rest) period of this experiment the urine was collected in a single portion for each day. On the iirst day 952 grams was excreted, containing 1 .39 per cent, or L3.2 grams nitrogen; the amount eliminated on the second day was 1,457 grams, with a nitrogen content of 0.96 per cent, or 14 grams; on the third day 1..">: J ,7 grams, with a nitrogen content of 0.91 per cent, or 14 grams; and on the fourth day 1,392 grams, containing 1.13 per cent, or 15.7 grams nitrogen. The total nitrogen eliminated in the urine during the whole period was, therefore, 56.9 grams, or L4. 2 grams per day. During the sec- ond (work) period the urine was collected in portions corresponding to eight-hour intervals, and its nitrogen content determined. The results are shown in the following table: v Table 27. — Amount of nitrogen eliminated in the urine {digestion eocpervment No. Period. First day: W.eight of urine Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen 8 a. m. to 4 p. m. 317 4.85 1.53 335 5.90 1.76 417 6.05 1.45 712 6. 34 4 p. m. to 12 p. m. 340 5.95 1.75 260 4.76 1.83 343 5. 73 1.67 4.87 1.19 12 i>. m. to S a. in. 197 4.26 2.16 255 5.23 2.05 291 4.54 1.56 270 3.97 1.47 Total. 85 1 15.06 850 15.89 1,051 16.32 1,391 15.18 29 During the third (rest) period the urine was as before collected in portions corresponding to eight-hour intervals. The amounts elimi- nated and the nitrogen in it arc shown in Table 28, which follows: Table 28. — Amount of nitrogen eliminated in the urine (digestion experiment No. 228). Period. Firsl day: Weight of urine grams. . Weighl "t" nitrogen do Per criit of nitrogen Second day: Weight of urine grams.. Weight of nitrogen do Percenl of nitrogen Third day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen 1 p, it to 12].. in. to Total. . III. « a. in. 639 157 5.50 4.43 .86 .97 K17 363 6.54 4.10 .80 1.13 635 470 4.70 5. 55 .74 1.18 369 272 5.54 3.97 1.50 1.46 l,fi'2X 15. 68 1 , 756 L5.59 1,607 16.02 1,006 14.80 As was the case in the preceding experiments, the daily balance of income and outgo of nitrogen was determined. Table 29. — Daily income and outgo of nitrogen in experiment No. 22. Periods. Time. Nitrogen. In food. In feces. In urine. Gain First period (rest) Second period (work) Third period i rest I... Days. 4 4 4 Grams. 17.85 17.59 17.55 Grams. Grams. Grams. 1. 33 14. 24 2. 28 1. 31 16. 61 . 67 1.29 L5.52 .71 EXPERIMENT NO. 23. This experiment began the third series reported in the present pub- lication, which was made with the same young men who had served as subjects of the preceding experiments. The diet contained less protein and energy than normal and was unchanged during the second or work period. Except in the second period, no appreciable amount of muscular work was performed. During the second period the subject of experiment No. 20 made the trip uphill 55 times. This was calcu- lated to yield 1,201,915 foot-pounds, or 41,565 kilogrammeters, equiv- alent to a total of 97 calories, or an average of 24 calories per day. The average results of the digestion experiment follow: Subject — Chemist A, age 30 years. Weighi (without clothing). — At the beginning of the experiment was 69.8 kilograms (153.5 pounds); at the end of the first period and the beginning of the second period, 68.4 kilograms (150.5 pounds); at the close of the second and the beginning of the third period, 67.7 kilograms (149 pounds); at the close of the experiment, 67.3 kilograms (148 pounds). Duration. — The three experimental periods, each of four days' duration, began with breakfast March 22, 26, and 30, respectively. 30 Table 30. — Reeu&ts of experiment No. 28. Labora tory iiiini- ber. Pood materials. Weight of ma- terial. Total organic matter. Nitro- gen. Protein. Fat. Carbohy- drates. Ash. Heat of com- bustion calcu- lated. 449 First Period I Rest). Digestion experi- ment No. 22k. Eggs Grams. 364 80 7, tiOO 100 280 120 900 40 320 800 drams. 88 70 966 99 252 109 604 36 320 2 Grams. 7.57 .24 41.80 .75 6.86 1.60 14.31 .50 Qrams. 47 2 261 5 43 10 90 3 Grams. 11 68 353 (•'n l ins. Grams. 4 2 59 ( 'alortes. 528 Hotter 626 Milk 352 94 189 99 60S 20 320 ISO Gelatin 605 Oatmeal 20 5 1 10 2 185 Rice 627 Bread 11 13 626 Potato chips Sugar.. Coffee .32 2 Total 2, 546 73. 95 463 506 1,577 83 13,917 Feces (water-free) Urine 531 117 6, 533 85 5. 74 66. 75 36 21 28 32 441 534 Amount digested. Coefficients of di- gestibility (per cent) . . .. 2,461 68.21 427 485 1,549 51 12, 942 96.7 92.2 92.2 95.9 98.2 61.5 93.0 Second Period (Work). Digestion experi- ment No. 225. Eggs 449 364 80 7,600 100 280 120 900 40 320 800 88 70 976 99 252 109 604 36 320 2 7.57 .24 41.04 . 75 6.86 1.60 14.31 .50 47 2 257 5 43 10 90 3 41 68 353 4 2 55 528 Butter 535 Milk 366 94 189 99 503 20 320 480 Gelatin 505 Oatmeal 20 5 1 10 2 is:, Rice rv_>7 Bread 11 13 526 Potato chips Sugar Coffee .32 2 Total 2, noti 73.19 459 506 1,591 79 13, 951 Feces (water-free) Urine 536 118 4, 274 87 5. 82 62.87 36 24 27 31 471 529 Amount digested . Coefficients of di- gestibility (per cent) 2, 469 67.37 423 482 1,564 48 12, 951 96.6 92.0 92.2 95.3 98.3 60.8 92.8 Third Period (Rest) . Digestion expt /•/- ment No. 226. 449 364 80 7,600 100 280 120 900 40 320 800 88 70 1,005 99 252 109 604 36 320 2 7.57 .24 41.04 .75 6.86 1.60 14.31 .50 47 2 257 5 43 10 90 3 41 68 381 4 2 60 528 Butter 540 Milk 367 94 189 99 503 20 320 480 < relatin 505 I latmeal 20 5 1 10 ■2 485 Rice 527 Bread 11 13 528 l'otato chips Coffee .. .32 2 Total 2, 585 73.19 459 534 1,592 84| 14,219 Feces (water-i reei Urine 541 121 5, 988 88 5. 88 68.35 37 26 25 33 457 527 Amount digested. Coefficients of . Periods. Nitrogen. Time. In food. First period, real — Second period, work Third period, rest ... Days. 4 4 4 Grams. 18.49 18.30 18.30 In feces. Grams. 1.44 1.46 1.47 In urine. Grams. 16.69 15.72 17.09 Gain( + ) or loss (-). drain*. +0.36 + 1.12 - .26 EXPERIMENT NO. 24. The experimental conditions in this were the same as in the pre- ceding experiment. The subject performed during the second or work period 1,349,157 foot-pounds, or 46,717 kilogramme ters of estimated muscular work. This was equivalent to 109 calories, or 27 calories per day. As in previous cases, the work consisted in walking up and down hill. The number of trips made was 75. Subject. — Chemist B, age 23 years. Weight (without clothing). — At the beginning of the experiment 56.1 kilograms ( 123.5 pounds) ; at the end of the first period and the beginning of the second period, 55.9 kilograms (123 pounds) ; at the end of the second and the beginning of the third period, 55.6 kilograms (122£ pounds); at the end of the experiment. 55.8 kilograms (122| pounds). Duration. — The three experimental periods, each of four days' duration, began with breakfast, respectively March 23, 26, and 30. 33 Table 34. — Results of experiment No. $4- Food materials Weight Total oi ma- organic terial. ' matter. First PERIOD (Rest). Digestion expt ri- iii mt No. .'.'.'. Eggs Butter Milk Gelatin Oatmeal Rice Bread Potato chips. Sugar Coffee Total Feces I water-free) Urine Amount digested. Coefficients of di- gestibility (per cent ) Second Period (Work). Digestion experi- ment No. ^28. i,, ams. 608 Ml 5,600 100 280 120 700 Ml 500 400 Eggs Butter Milk Gelatin Oatmeal Rice Bread Potato chips. Sugar Coffee Total Feces ( water-free) Urine Amount digested. Coefficients of di- gestibility (per cent) Third Period (Rest). Digestion expt ri- nu nt y_> s7 5. 3(] 54.58 34 37 16 23 451 492 Amount digested. Coefficients of di- : gestibility per cent i 2, 576 62 '.'5 394 461 1.721 53 13,965 96.7 92, 2 92.1 92. 6 99. 1 69.7 j 93.4 37 On the first day of the first (rest) period the subject excreted 842 grams of urine containing L.92 percent, or L6.2 grams nitrogen; on the second day 910 grams urine, containing L.69 per cent, or L5.4 grams nitrogen; on the third day the total urine excreted equaled 1.im;;> grams, its nitrogen content L.37 per cent, or 14. *> grams; on the fourth day of the period the urine excreted equaled L,697 grams with a nitrogen content of 0.89 per cent, or 15.1 grams. The total amount of nitrogen excreted in the urine during the period was, there- fore, 61.2 grams, or 15.3 grams per day. As was the case during the preceding experiments, the urine was collected in the second (work) period in portions corresponding to eight-hour intervals, and its nitrogen content determined. The results follow. Table 39. — Amount of nitrogen eliminated in tin urim {digestion experiment No. 231). Period. 8 a. m. to 4 p. m. 4 p. m. to 12 p. m. Fi^t day: Weight of urine gram<. . 344 Weight <>f nitrogen ■. do j 4.44 Per cent of nitrogen 1. 29 Second day: Weight of urine gram- . . 299 Weight of nitrogen do 5.17 Per cent of nitrogen 1. 73 Third day: Weight of urine grams. . 270 Weight of nitrogen do 5.02 Per cent of nitrogen 1.86 Fourth day: Weight of urine grams. . 277 Weight of nitrogen do 5. is Per cent of nitrogen 1.87 5. 39 1.61 7.20 1.86 5.85 1.90 319 6.06 1.90 12 p. m. to 8 a. m. Total. 190 869 3. 84 13. 67 2.02 165 851 3.48 15.85 2.11 155 733 3.68 14.45 2.31 215 811 4.19 15.43 1.95 The details of the amount of urine and nitrogen in it excreted during the eight-hour periods of the third (rest) period of this experiment are as follows: Table 40. — Amount of nitrogen eliminated intheurim (digestion experiment No. Period. First day: Weight of urine grams.. Weight of nitrogen do Per cent of nitrogen Second day: Weight of urine grams. . Weight of nitrogen do Per cent of nitrogen Third day: Weight of urine grain*-. . Weight of nitrogen do Per cent of nitrogen Fourth day: Weight of urine grams.. Weight of nitrogen do Per rent of nitiogen 8 a.m. 4 p. m. to to 4 p. m. 12 p. m. 322 5.22 1.62 562 6.18 1.10 180 2.75 1.53 1.33 4.93 1.53 365 5.62 1.54 242 304 4.02 5.02 1.66 1.65 12 p. m. to 8 a. m. Total. 3S0 1,182 3. .50 15.10 .92 1.119 3.67 H.7> 1.56 17o 720 3.40 11.77 1.94 215 761 3.89 12.98 1.81 38 The table below shows the daily balance of income and outgo of nitrogen during the whole experiment: Table 41. — DaUy income and outgo of nitrogen in experiment No. Periods. First period, rest Second period, work Third period, rest .. Time. Days. 4 4 4 Nitrogen. In food. In feces. In urine. j Gain. Grams. 17.22 17.08 17.08 Grams. Grams. 1.09 15.31 1.26 14. 85 1.34 13.65 Grams. 0. B2 - SUMMARY OF COEFFICIENTS OF DIGESTIBILITY. In the preceding pages data are given which show the amount of protein, fat, and carbohydrates digested, as well as the energy of the total digested food. Such data are summarized in Table 42. the results being compared with those obtained in the similar investigation pre- viously reported/' Table 42. — Summary of coefficients of digestibility of a simple mixed diet, and the energy available. Num- ber of experi- ment. 206 207 i 208 209 | 210 211 212 213 214 215 216 217 218 219 220 ' 221 222 223 224 225 226 •227 228 229 230 231 232 , Sub- ject. Character of experiment. Protein. Fat. Carbohy- drates! Energrv Rest Work Rest do Work Best do Work Rest do Work Rest do Work Rest do Work Rest do Work Rest do Work Rest do Work Rest Average, rest experiments: A. 6 experiments R. 6 experiments C 6 experiments Average, 18 experiments. Average, work experiments: A, 3 experiments B, 3 experiments €, 3 experiments Average. 9 experiments Average, all (27) experiments . Per cent, 91.6 91.2 92.2 92.0 91.5 91.5 92.4 92.6 92.9 92. 2 91.6 91.4 91.7 92.0 91.7 92.6 92.5 I 92.7 92. 2 92. 2 91.9 92.2 91.9 91.6 93.8 92.8 92.1 91.9 91.8 92.7 Per cent 95.9 96.4 96.7 94.0 94.0 94.1 94.3 92. 7 94.8 94.2 95.5 95. 2 92.4 93.8 93.0 92.4 94.' 4 95.9 95.3 95.1 95.8 93.6 93.9 96.9 94.1 92.6 95.5 93.9 94.2 92.1 Per cent. 98.3 98.4 98.4 98.3 98.6 98.4 98.4 98.4 98.1 99.1 98.7 96.8 99.0 98.5 98.2 98.3 98.4 94.5 98.7 98.5 99.0 99.1 ,b Per cent. 92.6 92.7 93.0 93.0 92.9 93.0 93.1 93.0 93.4 92. S 93.3 92.6 92.5 93.6 92. 7 92.8 93.6 93.1 93.0 92.8 93.1 93.3 93.1 93.2 93.9 93. 5 93.4 92.8 93.0 93.3 92. 2 94.5 98.4 ' 93.0 91.7 91.8 92.6 95.7 93.8 93.3 98.2 | 98.7 98.9 1 92.9 93. 2 93.4 92.0 94.3 98. 6 93.2 93.1 a U. S. Dept. Agr., Office of Experiment Stations Bui. 89. 89 From the table it appears thai there was practically no difference in the average thoroughness of digestion of the ration when tin* sub- jects rested unci when they performed rather severe muscular work. Slight variations are noticeable in the coefficients of digestibility obtained with the different subjects, but these are not sufficient forgen- eral deductions. Individuality appeared to have much less effect upon the digestion than might be expected. The average results agree quite closely with those previously obtained when it is remembered that the diet in the two series of experiments though similar was not the same. Considering the experiments as a whole, the differences in coefficients of digestibility between the periods of work and rest are Less marked than those observed when the conditions as regards work performed were uniform. This is strong evidence that the average results of a considerable number of digestion experiments may be assumed to actually represent the digestibility of the different nutrients in a given diet, and that such averages may be used in calculation. METABOLISM OF NITROGEN. The income and outgo of nitrogen was determined in the experiments reported in this bulletin, the special object being to secure information regarding the nutrients, which are the actual source of muscular work. It was assumed that if protein was required for performing external muscular work more nitrogen would be excreted in the urine under the experimental conditions in the period in Avhich muscular work was performed than in the periods in which the subject remained as inac- tive as possible. There are those who maintain that muscular work is performed at the expense of nitrogen- free nutrients, and that under ordinary circumstances protein is not the source of energy, but is required for the formation and repair of body tissue. Other physiolo- gists hold that while nitrogen-free nutrients are usually the source of muscular energy, yet, if the work is protracted enough, or severe enough to induce labored breathing, the energy must be supplied by protein. Judging by the results of the investigations conducted under the auspices of this Department, it appears that, provided the carbohy- drates and fat in the diet are abundant and the protein is not excessive, the nitrogen-free nutrients are the usual source of energy for external muscular work. In the early experiments made at the University of Tennessee the diet was quite abundant, and under the different experimental condi- tions little change in the amount of nitroo-en excreted in the urine was observed, which could be attributed to an increased metabolism of protein in the work periods. In the present experiments the diet was more limited in amount, though in the majority of eases it was normal in the proportion of nitrogen-free to nitrogenous nutrients. 40 The balance of income and outgo of nitrogen, as well as the available energy in a food, and the average heat equivalent of the work per- formed in the different work experiments, is shown in the following table: Table 43. — Daily incorru and outgo of nitrogen and energy in metabolism experiments Nob. 17-25, with work actually measured. a, . a -- -- •_ IS 19 20 21 22 23 24 25 206 207 208 209 ■Jio 211 212 213 1214 215 •JIG ■217 218 219 220 221 222 223 224 225 226 227 228 229 1230 ^231 232 Character of experi- ment Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Rest . Work Rest . Nitrogen. II Kgs. A -0.45 A A R 4- .34 B - .34 B + .23 c - .23 (' e A -1.13 A A R - .45 B + .45 R - .23 C -1.13 (' + .68 c - .68 A -1.36 A - .23 A - .45 R - .34 B - .34 R -f .23 (' <"' C - .45 Gins. 20.88 20.08 20.48 18.54 17.94 18.24 18.93 18.33 18.63 19.43 19.07 19.04 17.25 16.99 16.95 17.85 17.59 17.55 18.49 18.30 18. 30 16.30 16.16 16.16 17.22 17.08 17.08 Gms. 1.75 1.74 1.60 1.51 1.51 1.57 1.44 1.37 1.35 1.52 1.59 1.(12 1.44 1.35 1.41 1.33 1.31 1.29 1.44 1.46 1.47 1.29 1.35 1.38 1.09 1.23 1.34 Gms. 17.56 17.92 17.61 13. 01 14.28 I 14.1s 14. 29 16. 44 16.77 17.98 16.75 17. 45 12. 22 13.73 13.66 14. 24 15. 61 15. 52 16.69 15. 72 17. 09 12. 53 13.11 14.19 15. 31 14. 85 13. 65 Gms. + 1.57 4- .42 +1.27 +4.02 +2.15 +2.49 4-3.20 + .52 + .51 - .07 + .73 - .03 +3.59 +1.91 +1.88 +2.28 + .67 - .74 + .36 -1.12 - .26 +2.48 +1.70 - .59 + .82 + .97 +2.09 Energy, Work measured. Calo- ries. 3,960 3, 912 3,898 3. 687 3, 651 3, 640 3,848 3,812 3,802 3, 442 4,016 3.4S3 3.175 3,748 3. 206 3. 361 3, 932 3, 392 3. 479 3,488 3. 555 3.272 :;.27s 3.327 X. 522 >28 g - « = ~ Galo- rit 8. vies. 143 149 142 143 124 lis E - - < 126 133 133 128 126 130 128 137 134 132 in; ion 119 140 133 123 114 118 101 111 136 136 i 124 122 113 121 114 129 125 127 108 127 lio 153 lis 132 114 132 118 116 109 116 ss 126 104 124 113 123 ties. 3,668 3,627 3, 626 3,428 3.390 3,384 3,583 3, -546 3. 550 3,183 3.747 3.224 2. 937 2,972 3,118 3.157 3. 236 3.23s 3. 309 3,053 3, 051 3.102 3.308 3,300 3, 341 K 521 532 486 494 503 493 432 428 461 448 463 473 506 470 409 406 452 463 <, rums. < j rums. :.17 J- 551 47 545 539 521 505 456 460 579 572 570 562 -568 563 550 646 1840 1781 1751 1885 1856 1517 1515 1428 1443 lo77 1600 1573 1565 48 35 90 83 Percent. 21.33 , 21. 43 24. 21 25. 11 22.18 22. 1-1 21. 19 21.20 21. 77 23.13 18.67 19.39 19. 98 21.47 20.81 21.11 IS. 10 16.54 , 17.31 16.02 | 16.20 18.75 19.04 18.04 I 17.87 17.61 ! IS. 00 i 16.35 16. 21 /'' /■ et. 31.15 30.78 26. 45 25.48 26.47 27.38 27. -56 27.03 24. 03 24.48 24. .50 23.82 21.39 20.07 23.12 22.79 24.39 23. 31 Per cent. 43.69 44.03 46.86 46.37 44. 34 43.00 46.39 46.77 51.33 •50.73 .50.04 49.70 56. 71 57.36 53. 57 52. 34 51.31 52.11 18.60 19.46 61.24 59.27 18.43 18.97 62. 43 60.59 17.64 18. 01 63.84 62.85 19.40 19.00 58. .50 19. 26 18.73 59.65 60. 26 19.25 17.86 59.99 60.88 18.07 18.50 62. 86 62.-56 ft r ct. 3.83 g. 76 3.94 4.08 4.09 3.87 3. 45 3.35 3.23 3.18 3! 40 3.50 3.47 2.79 3.17 2.60 3.13 2.50 2.94 3.32 3.46 3.05 3.14 3.15 3.26 2.72 2.73 It will be seen that the agreement between the composition of the ration as shown by the analysis of composite samples and as computed on the basis of analyses of individual foods is quite close. When the results of duplicate analyses of the same composite sample were com- pared the same close agreement is found. In accordance with the usual practice, these data are not reported. In all cases the discrepan- cies are not greater than are to be expected from the analysis of different samples of such foods as meat, fish, etc.. or in some cases even in duplicate analyses of the same sample. Furthermore, it must be remembered that the calculated composition of the ration includes the result of all the errors in the analysis of the different foods. The proportion of error in the anlysis of composite samples it would 48 appeal- must be lower, as the total Dumber of determinations is nol nearly as Large. It is interesting to compare the coefficients <>t' digestibility obtained in the different work and rest periods in the earlier experiment- at the University of Tennessee and those reported herewith when the composition of the ration is obtained by the two methods. Table 4">. — ( '<>< ijiri, ntsof digestibility of nutrients computi dfrom composition of individual food materu Is and from thai of composite samples. Character of analyses. Experiment No. 58: By individual analyses By composite analysis. . Experiment No. 56: By individual analyses. By composite analysis. Experiment No. 59: By individual analyses By composite analysis. . Experiment No. 62: By individual analyses. By composite analysis.. Experiment No. 65: By individual analyses By composite analysis . Experiment No. 99: By individual analyses. By composite analysis. Experiment No. 102: By individual analyses. By composite analysis. . Experiment No. 106: By individual analyses Bv composite analysis . Experiment No. 108: By individual analyses. Bv composite analysis. . Experiment No. 206: By individual analyses By composite analysis. . Experiment No. 209: By individual analyses By composite analysis. . Experiment No. 212: By individual analyses By composite analysis. . Experiment No. 215: By individual analyses By composite analysis. . Experiment No. 218: By individual analyses By composite analysis. . Experiment No. 224: By individual analyses By composite analysis. . Experiment No. 227: By individual analyses By composite analysis. . Protein. Fat. ^Sfi 7 " Ash. Energy. Per <■> at. 94.4 94.4 94.2 94.3 94.2 94.3 91.7 91.8 93.3 93.3 92.7 93.2 91.4 91.7 92.9 93.4 92.8 92.9 91.6 91.9 92.0 92.4 92. 4 92.5 92.2 92.3 91.7 91.6 '.''J. 2 92.4 92. 2 92. 1 /•< ;• cent. 96.9 96.9 94.9 94.9 94.9 95.0 97.0 97.0 96.7 96.8 95.7 95.6 ss. -1 87.4 95. 5 95.4 94.5 94.2 95.9 96.1 94.0 94. 2 94.3 94.4 94.2 94.1 92.4 92.2 95.9 95.5 95. 9 drates Per cent. 96.1 96.2 98.0 98.0 96.5 96.5 95.9 95.9 97.6 97.6 96.8 98.2 98.2 96.1 96.0 97.5 97.6 97.7 97.6 98.3 98. 2 98.2 98.3 98.3 98.3 Percent. Percent. 66. 7 90. 8 66.0 65.9 90.8 67.4 66. 7 88. 9 66.7 55.3 91.2 56.4 61.5 91.2 62.5 52.4 90.0 47.4 56.3 88.8 56. 3 62. 9 S9. 4 63.9 56.8 90.1 56.8 i 56.0 61.0 6/.1 72.7 67.6 72.4 68.1 60.0 64.4 65.3 61.5 .... 62. 8 2 The agreement between the results obtained by the two methods is again seen to be very close. From the results of the above comparisons it seems fair to conclude that the composition of a given diet may be learned with reasonable accuracy by the analysis of a composite sample made up of aliquot portions of the different foods in the ration, and that this method may be advantageously followed in digestion experiments and similiar investigations where the amount of analytical work is at best neces- sarily large. ■Hi!