ON THE MAMMALIAN NERVOUS SYSTEM. 311 



size has been roughly indicated previously ; this will, however, be more clearly 

 exhibited by the consideration of the ratio which a similar comparison between the 

 difference in the cord and in the posterior root of the Cat shows : 



Average Cat cord _ "032 __ J/5 



Average Cat posterior root '022 1 



It is probable therefore that the larger difference is in some way correlated with 

 the structure of the cord and the trophic and other physiological influences which 

 that structure implies. 



This explanation is supported by an analysis of the results obtained in the two 

 species of animals when the cord is placed under different conditions as regards its 

 central connections. Such analysis involves the grouping together on the one hand of 

 all those determinations in which the cord was still in connection with the cerebrum and 

 its central end investigated, and on the other hand of all those in which the portion 

 of cord examined was that of the lower fragment unconnected with the cerebrum. 



The first group shown in Appendix B, III., gives the average result in the case of 

 the lower dorsal cord of fourteen Cats, this average being '034 Daniell ; the highest 

 amount observed being '046, the lowest '025. 



It also gives the average result in the case of five Monkeys, this being '025 Daniell; 

 the highest reading being '029, the lowest '018. 



If now, we turn to the second group, the average in the Cat of all the readings in 

 the dorsal and lumbar regions respectively when the Cat's cord is severed from the 

 brain, amounts to : 



Dorsal region, 24 cases, average '029 

 Lumbar ,, 10 '033 



34 cases 



Gross average = '03 Daniell. 

 Highest = '043 ; lowest = '014. 



In the Monkey a similar average of four sets of experiments gives '019 Daniell; 

 highest '027, lowest '013. 



A comparison of the two groups of results may now be made as follows : - 



Cat- 

 Cord connected with brain '034 



Cord severed from brain '03 



Monkey 



Cord connected with brain '025 



Cord severed from brain '019 



