ANATOMY AND PHYSIOLOGY OF THE SPINAL CORD. 403 



which contribute to the same movements in the body. 

 Before noticing these, however, a few remarks will be given 

 on the excitability of the cord itself. 



It is held by many physiologists, that the columns of the 

 cord correspond to the roots of the spinal nerves in this; 

 that while the anterior columns are possessed of no sensi- 

 bility the posterior are acutely sensitive throughout. M. 

 Chauveau has carefully investigated this matter, having 

 sacrificed as many as eighty horses in his experiments, and 

 his conclusions are such as to modify greatly the above 

 statement. The following are his results : 



1st, On the Cord separated from its connection with the 

 Brain. In this case, when the division of the cord was made 

 in the upper or middle third of the neck, respiration was 

 kept up artificially. On pricking or scratching the surface 

 of the anterior or lateral columns, care being taken not to 

 come in contact with the motor nerves, no evidence of 

 sensibility was obtained. On treating similarly the surface 

 of the posterior columns, contractions took place in the 

 muscles supplied by the adjacent motor nerves. When 

 slightly irritated, muscular contractions took place on the 

 same side only ; when more actively irritated, similar effects 

 were noticed on the opposite side, and on both of a more 

 extensive character. 



2d, On the Spinal Cord connected with the Brain. Scratch- 

 ing of the anterior and lateral columns produced, as before, 

 no result. Irritation of the posterior columns led to signs 

 of pain and active (involuntary) muscular contraction. 

 Varying the amount of irritation produced effects similar 

 to those observed in the detached end, and the pain was 

 most lively when the outer border of the column was 

 touched, becoming less and less so toward the superior 

 median fissure. 



