108 



VETERINARY PHYSIOLOGY 



which reflex action is produced (p. 82); (2) that other parts 

 of the ingoing nerves run up the spinal cord to act upon 

 some part of the brain the activity of which is related 

 to those chancres in consciousness which we call sensa- 

 tions. 



(o) Hemisection of Spinal Cord. — If only one half of the 

 spinal cord is cut across all sensation of changes of temperature, 

 and all sensation of pain are lost on the opposite side below 

 the level of section, but tactile sense is partially lost for some 

 distance below on the same side, and further down on the 

 opposite side. The proprioceptive sensations are lost on the 

 same side. 



The fibres connected with pain and with heat and cold 



Fig. 47. — To show the Ascending Degeneration in the Spinal Cord. 1, after 

 section of the posterior roots. 2, after hemisection of the cord. 



receptors must cross the middle line at once and run up the 

 opposite side of the cord, while those connected with touch 

 must ran for some distance, probably in part, right up 

 the same side of the cord. Those connected with the 

 muscle-joint sense must run up the same side of the 

 cord. (For outgoing fibres see p. 19-5.) 



(4) Ascending Degenerations of Cord. — Taking advantage of 

 the fact that nerve fibres when separated from their cells die 

 and degenerate (p. 76), light has been thrown upon the course 

 of these fibres in man and apes by studying the degeneration 

 which follows: — 



1. Section of a series of posterior roots inside the ganglia. 



2. Section of one half of the cord. 



