ON THE MAMMALIAN NERVOUS SYSTEM. 



505 



posterior column having been divided at the 9th dorsal vertebra, the left 1st lumbar 

 posterior root was excited, and the electrical changes in the cord noted galvano- 

 metrically at the same time that the muscular movements were observed. 



It will be seen that the electrical change in the dorsal region of the cord was 

 indicated by an effect of 55 in the galvanometer, when the lateral column on the side 

 of the excitation was uninjured ; whereas hemisection between the root and the 

 observed region cut down the galvanometric effect to only 7. Before the interruption 

 by the hemisection, a reflex contraction was observed during the excitation in all the 

 muscles supplied by the various nerve segments between the excited root and the 

 observed area of cord, whilst, after the section, such reflex contraction was limited to 

 the piece of cord below the hemisection. The particulars of this second experiment, 

 which appear to suggest that the internuncial fibres are localised in the lateral 

 column, are as follows : 



Cat 376. Cord divided, and peripheral end connected to the galvanometer at the 

 intervertebral disc between the 8th and 9th dorsal vertebrae, section of the left 

 posterior column opposite 13th dorsal vertebra. 



Left hemisection of the cord was then performed at disc between 13th dorsal and 

 1st lumbar vertebra?. 



(2.) Descending Discharges. 



While PFLUGER'S law concerning the upward internuncial discharge of spinal nerve 

 centres undoubtedly prevails, nevertheless the anatomical investigations of LOCKHART 

 CLARKE, the physiological observations of BROWN- SEQUARD, and the anatomical 

 researches of GOLGI, recently confirmed by RAMON Y CAJAL, show that there must 



MDCCCXCI. B. 3 T 



