Kanson, Spitial Nerves. 113 



merated in the same individual nerve, a rather constant ratio of 

 approximately i fiber to 3.2 cells was obtained. The first tv^o 

 specimens v^ere 72 days old and w^eighed about no grams, the 

 third was six months old and weighed 188 grams. 



TABLE III. 



Ratio of Spinal Ganglion Cells to Dorsal Root Fibers (Ranson). 

 Specimen. Number of Cells. Number of Fibers. Cells per Fiber. 



72 days 7,721 2,472 3.1 



72 days • 8,116 2,394 • 3.3 



6month.s 8,624 2,689 3-^ 



The number of cells in a given spinal ganglion exceeds the 

 number of medullated fibers in the corresponding root; this excess 

 holds alike for frogs and mammals, although the actual percentage 

 of the excess varies greatly. Hatai and Hardesty ascribe to the 

 anaxonic cells the responsibility for this condition; but, since we 

 know that these cells do not exist in any appreciable number, we 

 are thrown back upon the non-medullated fibers of the small cells 

 as the chief source of the discrepancy. While it is possible that 

 the majority of these non-medullated fibers do not push out into 

 the dorsal root, it seems probable that the number of cells in the 

 spinal ganglion does not exceed the number of axis cylinders in 

 the dorsal root by so large a number as it does the number of mye- 

 lin sheaths. A count of the dorsal root fibers obtained by a dif- 

 ferential axis cylinder stain is the logical method of answering this 

 question. 



5. The increase in the number of medullated fibers in the grow- 

 ing animal. — Hardesty ('05) has shown that, when his frogs were 

 arranged in a series of increasing body weight, there was a general, 

 though not very regular, increase in the number of fibers in the 

 ventral and dorsal roots as well as in the peripheral nerves. 



The white rat however in the hands of Hatai ('03) has given 

 uniform results, showing a regular increase in the number of med- 

 ullated fibers both in the ventral and dorsal roots. 



The n C. nerve of the white rat shows more variability; in a 

 general way however the number of fibers is increasing. The 

 increase is, however, by no means as rapid, nor is there such a 

 large number of fibers added as in the nerves studied by Hatai. 



These observations are recorded in the accompanying table. 



