LIBRARY 
 STATE esfbt^T ^9^RD 
 
 ET-310 
 
 United States Department of Agriculture 
 
 Agricultural Research Administration 
 
 Bureau of Entonaology and Plant Quarantine 
 
 A TECHNIQUE OF GRAIN ORIENTATION 
 FOR RADIOGRAPHIC ANALYSIS 
 
 By Norman M. Dennis 
 Division of Stored Product Insect Investigations 
 
 The accurate examination of wheat or other grains for hidden infes- 
 tation by the radiographic method requires a systematic arrangement of 
 the kernels on the X-ray film. If random arrangements are used, con- 
 siderable time may be consumed in reading the finished radiograph. 
 Expensive films, chemicals, and more time may be wasted by too 
 loosely grouping the kernels. At the other extreme, a crowded sample 
 will produce results that make accurate evaluation impossible. 
 
 Various techniques have been suggested for orientation of the 
 kernels of grain in preparation for the radiographic examination. A 
 series of small lateral V-shaped furrows produced by crimping a heavy 
 grade of Cellophane has been used. The lateral furrows are filled by 
 sprinkling the sample of grain over them. A slight jar will upset the 
 arrangement. Grooved plastic has been tried, but radiographic details 
 in the sample are obscured by the X-ray's transversing the plastic. 
 Assorted grills or pens have been used, but they too are tedious to load. 
 
 The soda-straw technique described herein has been found to be a 
 very satisfactory method for conserving film as well as reducing the 
 preparation and examination time of each sample. It also affords a 
 conveni^ent way of handling the grain samples for storage, identification, 
 and reexamination at a later date, if this be desired. 
 
 Soda straws are inexpensive and can be obtained very easily in 
 various diameters. The choice of diameter will depend on the kind of 
 grain being examined. The common size 4 mm. in diameter is ideal 
 for wheat kernels. Cellophane soda straws are more convenient to 
 work with, since the tightness of the packed wheat kernels inside the 
 straw can be observed; however, with a little experience comparable 
 results can be obtained with paraffin paper straws. 
 
 Individual soda straws can be loaded with wheat kernels in about 
 2 seconds with the use of suction from a small vacuum pump or aspira- 
 tor (fig. 1). A good holder for the straws can be quickly constructed 
 from a 3-inch section of 5-mm. o. d. glass tubing having a wall thickness 
 of 1.D5 mm. A 1-inch section of light gum -rubber tubing 3/16 inch i. d. 
 
is slipped l/2 inch on one end of the section of glass tubing. The remaining 
 l/2-inch end of rubber tubing fornris a receptacle cup for the soda straws. 
 The other end of the section of glass tubing is connected to the vacuum 
 line. The internal diameter of the glass tubing is small enough to prevent 
 sucking wheat kernels down the vacuum line. The irregular shape and 
 size of the wheat kernels make it impossible to clog the straw by reducing 
 the vacuum during the loading operation. When the straw has been filled, 
 it is removed from the receptacle cup and each end is crimped with the 
 fingernail to confine the kernels. Each straw can be marked with ink or 
 other method of identification. 
 
 A fully loaded 8 1/2 -inch soda straw will hold about 45 wheat kernels. 
 These kernels will remain in the same order until the straw is unloaded. 
 One-hundred and forty-four of these soda straws, giving a total of 6,480 
 kernels, can be radiographed side by side in a grain X-ray machine on a 
 14- by 17 -inch X-ray film (figs. 2% 3). Arrangement of the straws and the 
 number of kernels radiographed per sample are of course optional. The 
 loaded straws can be grouped with rubber bands and stored in 2 -quart 
 Mason jars or any convenient container. 
 
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