326 Journal of Comparative Neurology. 



at the two levels of both the roots and trunk. In case of the 

 roots, counts were made of the fibers contained in sections 

 taken (i) as near the spinal cord as possible with the certainty 

 that the sections were intact ; and (2) of sections taken as near 

 the spinal gangHon as would allow them at the same time to be 

 free from spinal ganglion cells. In the longer roots, additional 

 counts were made from sections taken midway between the 

 cord and spinal ganglion. In case of the nerve trunks, the 

 enumerations were made of the fibers in a section taken (i) im- 

 mediately after the trunk emerges from the spinal ganglion ; 

 and (2) of the fibers in a section taken just before the ramus 

 conmiunicans appears. Careful counts were also made of the 

 fibers contained in the dorsal branches of each nerve. 



The nerves were stained with osmic acid, paraffin sections 

 were made from 3 to 4 micra in thickness, and the counts were 

 made with the application of a photographic method fully de- 

 scribed in the former paper. 



The following were among the conclusions reached : i . 

 The number of fibers in the ventral roots decreases as the root 

 passes from the spinal cord towards the spinal ganglion, 2. 

 The same is true for the dorsal root as it passes front the 

 spinal ganglion towards the spinal cord, 3, A section of the 

 nerve trunk taken close to the spinal ganglion contains (dorsal 

 branches excluded) more fibers than a section of the trunk 

 further distal. 



These differences in the number of fibers were interpreted 

 as merely an expression of the manner and rate at which the 

 larger frog acquires, as the result of growth, the greater num- 

 ber of fibers in its spinal nerves. 



4. The sum of the fibers in the trunk and dorsal branches 

 together always considerably exceeds the sum of the fibers 

 contained in the two roots. 



The material from which these conclusions were drawn was 

 obtained from only two specimens. These differed very slightly 

 in weight and were also taken at about the same season of the 

 year. 



Since the publication of these observations, it has been 



