ft I Witt' I 
 
 
 U. S. Department of Agriculture, Forest Service 
 
 FOREST PRODUCTS LABORATORY 
 
 In cooperation with the University of Wisconsin 
 MADISON, WISCONSIN 
 
 SCHOOL OF FORESTRY U 
 
 \ 
 
 UNIVERSITY OF FLORiOA 
 
 NEWLY DISCOVERED MICROSCOPIC STRUCTURAL 
 UNITS OF WOOD FIBERS 
 
 By GEORGE J. RITTER 
 Senior Chemist 
 
 and 
 
 R. M. SEBORG 
 
 Assistant Chemist 
 
 R loii 
 
 Published in 
 
 INDUSTRIAL AND ENGINEERING CHEMISTRY 
 
 December, 1930 
 
Digitized by the Internet Archive 
 
 in 2013 
 
 http://archive.org/details/newlydiscOOfore 
 
HEWLY DISCOVERED MICROSCOPIC STRUCTURAL UNITS OF V/OOD FIBERS^ 
 
 By 
 
 GEO. J. RITTER and R. M. SEBORG 
 
 Results published by Ritter (1_) regarding the dissection of wood 
 fibrils by chemical means showed that the smallest structural units of the 
 wood fiber which had been isolated at that time were fusiform bodies. 
 They are short, spindle-shaped units which, when arranged parallel to one 
 another with an overlapping of the pointed ends, form the fibrils. The 
 fibrils are long, slender, fi lament-like structures, arranged to form the 
 fibers. 
 
 Careful microscopical examination of the fusiform bodies after 
 various treatments suggested that they are composed of still smaller 
 structural units. At the tine of the meeting of the American Association 
 for the Advancement of Science, Des Moines, Iowa, December 1$29> sufficient 
 progress had been made in the study to warrant the following prediction (2); 
 
 It is quite probable that still smaller microscopic building 
 units in the fusiform bodies will be discovered in the near future, 
 and that the source of the optical properties described in the 
 preceding paragraphs will then be found in the newly discovered 
 uni t s . 
 
 Recently, separation of the fusiform bodies into smaller units 
 was accomplished at the Forest Products Laboratory, but suitable photo- 
 micrographs of the results were obtained only after much experimentation 
 and difficulty. 
 
 Materials 
 
 The materials used in this study consisted of two batches of 
 mixtures of fibrils and fusiform bodies which were prepared from delignified 
 i.hite spruce fibers. One batch was prepared by the sulfuric acid method; 
 the other, "by chlorination in the sunlight. 
 
 —Presented before the Division of Cellulose Chemistry at the 80th Meeting- 
 of the American Chemical Societ", Cincinnati, Ohio, September 8 to 12, 
 
 1930. 
 
 R10$U 
 
Procedure and Results 
 
 Small samples of the mixtures containing fibrils and fusiform 
 bodies were treated on glass slides with phosphoric acid (~Jo percent) at 
 approximately 75° C TThen slight pressure was applied to the cover glass 
 over the specimen, the fusiform bodies separated into smaller units. 
 
 The newly discovered units (Figure 1) are spherical in form 
 when detached from the mother unit. They are approximately 0.^5 micron, 
 or U5OO A. in diameter, which is nine times the length of the cellulose 
 micelle revealed by the X-ray diffraction pattern. Since these units have 
 not been observed in the fusiform bodies, their original form is unknown, 
 but from observed optical properties it would seem that the shape is other 
 than spherical. 
 
 Optical P r operties 
 
 Previously described structural cellulose units (2) showed 
 between crossed Nicol prisms an increasing degree of sharpness in the 
 angles of minimum and maximum luminosity with decreasing size of unit. 
 In other words, the parallelism of the crystalline structure which exhibits 
 the effect in polarized light was greater in the smaller units. Such a 
 condition would be expected from the fact that there is less opportunity 
 for variation in the parallelism of crystalline arrangement in the smaller 
 than in the larger units which are composites of the small ones. It was 
 found, however, that between crossed Nicol prisms the isolated spherical 
 units were uniformly luminous in all positions, indicating a random 
 arrangement of the crystalline structure. Such a disarrangement in the 
 internal structure of the new units would result during the deformation 
 of an angular body to a spherical one. This conclusion is confirmed by 
 the fact that it would be impossible to build up a solid structure with 
 spherical units. 
 
 The results herein described suggest a future study in which the 
 spherical units may be isolated under minimum swelling conditions, so as 
 to reduce the possibility of deforming them. If the same units can be 
 obtained by such a method, which the writers believe is possible, their 
 optical properties should be similar to those of the fusiform bodies. 
 
 Literature Cited 
 
 1. Hitter, Ind. Eng. Chera. , 21, 28^ U92S). 
 
 2. Hitter, J. Forestry, 28, 533 (1930) , 
 
 R109U -2- 
 

 
Figure 1. — Spherical units. 7°0X. 
 
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