Proceedings of the Association of American Anatomists 519 



ON THE NUMBEE AND SIZE OF THE SPINAL GANGLION CELLS AND 

 DORSAL ROOT FIBERS IN WHITE RATS OF DIFFERENT AGES. 

 By He^^ry H. Doxaldson. 



Dr. Donaldson presented some results obtained by j\Ir. Hatai from 

 his studies on the spinal ganglion of the white rat during the growing 

 period. 



Four rats were used, their body weights being 10, 24, 68, and 167 

 grams, respectively. In each rat the number of cells in the ganglion 

 and the number of fibers in the dorsal nerve root of the sixth cervical, 

 tourth thoracic, and second lumbar was determined. On comparing 

 the number thus obtained, it was possible to draw the following con- 

 clusions : 



1. In the spinal ganglia the number of cell bodies is constant between 

 birth and maturity; there is, of course, some individual variation in 

 this number. 



2. The fibers of the dorsal nerve roots are more than twice as numer- 

 ous in the 167-gram rat as in the 10-gram rat, and the intermediate 

 weights show intermediate numbers in the roots. 



3. Since this is the case, it follows that the ratio between the num- 

 ber of cells in the ganglia as compared with the number of fibers in the 

 dorsal nerve root steadily decreases. In the youngest stage, there may 

 be as many as eleven cells in the ganglion for each fiber in the dorsal 

 nerve root, while in the case of the most developed nerve, there are 

 still 2.7 cells for each fiber. 



It appears that the new fibers are formed by the outgrowths of cells 

 present in the ganglion from the earliest stage. 



Studies on the general activity of the rat show that they are most 

 active when weighing from 25-35 grams, and therefore, at a time when 

 the number of fibers in the dorsal nerve roots is still very incomplete. 



THE NEUROGLIA OF THE OPTIC NERVE AND RETINA OF CERTAIN 

 VERTEBRATES. By G. Carl Huber. 



These observations embrace a study of the structure and distribution 

 of the neuroglia of the optic tract, chiasm of the nerve and retina of 

 the dog, cat, dove, tortoise, and frog, and also fragmentary observations 

 on the neuroglia of these structures as found in man. 



In this study, Benda's recently published method for staining the 

 neuroglia was used; this the writer has found applicable for staining 

 the neuroglia of vertebrates other than man. 



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