286 Journal of Comparative Neurology and Psychology. 



the experiment. It was anticipated that the section of the nerve 

 would not be nearly as destructive of spinal ganglion cells in the 

 adult, as it had been in the younger animals; and the results ex- 

 pressed in Table X came as something of a surprise to the writer. 



TABLE X. 



Showing the Effect of Cutting the II C. Nerve in Adult Rats (140 Days Old) 



which Survived 120 Days. 



TABLE XI. 

 Showing the Influence of the Age of the Animal and the Length of the Post- 

 operative Period upon the Effect of Cutting the II C. Nerve in the White Rat.' 



'The figures in parentheses indicate the number of cases from which the averages were obtained. 



From Tables X and XI it will be apparent that there was found 

 a slightly greater number of cells in the spinal ganglia of the ani- 

 mals operated on when already adult, than in the first set of young 

 rats, but fewer than in the second set. It is believed that the 

 diflFerence is in each case merely a matter of individual variation 

 in the original ganglia, and is, therefore, of no consequence. That 

 the section of the nerve should entail practically the same effect 

 upon the spinal ganglion, whether it is made in the young or in 

 the adult animal, is a matter of a good deal of interest and a result 

 quite contrary to precedent. It is the more difficult to understand 

 because at least 30 per cent, more meduUated afferent fibers were 

 cut in the operation upon the adult than in that upon the young 

 rat (p. 274), and it is hard to see how this should have been so 

 exactly compensated for by a greater resistance of the adult neu- 

 rones. There is a possibility that even in the rat twelve days old 



