64 



have been considered as demonstrating that there is no crossed 

 action in the spinal cord. 



One of these experiments of Galen consisted in the transver- 

 sal section of a lateral half of the spinal marrow. After this 

 operation the animal was paralyzed in all the parts situated be. 

 hind the section, on the same side, so that the palsy was on the 

 right side of the body when the right side of the spinal cord was 

 divided, and vice versa. 



The second experiment consisted in a longitudinal section on 

 the middle line of the spinal cord so as to separate into two late- 

 ral halves the part of that nervous centre supplying nerves to the 

 posterior limbs. After this operation the animal was able to 

 walk. 



Galen, in these two experiments did not examine the state of 

 the sensibility. He speaks merely of the voluntary movements. 

 Nevertheless his researches were considered in this century as 

 completely proving that there is no crossing of action in the 

 spinal cord, either for sensibility or for voluntary movement. 



The following experiments will prove that there is a crossing 

 of action for sensibility in that organ : 



1st. If a lateral half (i. e. the posterior and the antero-lateral 

 columns and the gray matter of one side of the spinal cord), is 

 divided transversely at the level of the tenth costal vertebra, on 

 a mammal, it is soon evident that the sensibility is much dimin- 

 ished in the posterior limb opposite to the side of the sections. 

 On the contrary the sensibility instead of being lost appears 

 much increased in the posterior limb on the side where the sec- 

 tion has been made. 



2d. If, instead of one transversal section of the spinal cord, 

 two, three, four or many more are made on the same lateral half 

 of that organ, the same results are obtained. 



3d. If, instead of mere sections, a removal of a part of a 

 lateral half of the spinal cord, is effected, the same results are 

 still obtained. In performing this experiment a longitudinal 

 section, one inch in length, from behind forward, is made in the 

 median plane of the spinal marrow, and then two transversal sec- 

 tions on a lateral half are made at the extremities of the longi- 

 tudinal section, so that a part of the cord is completely separa- 

 ted from that organ and afterwards removed. 



