280 NERVOUS SYSTEM. 



Transmission of Motor Stimulus in the Cord. The 

 antero-lateral columns of the cord, both the white and the 

 gray substance, are entirely insensible to direct irritation, 

 and conduct the motor stimulus from the centres to the 

 periphery. This statement may be accepted, as the result 

 of positive demonstration, with very little qualification. 



If the posterior columns of the cord be divided or even 

 removed for a certain length, the animal retains the power 

 of voluntary motion intact. It is supposed by Dr. Brown- 

 Sequard that the white substance of the antero-lateral col- 

 umns, in addition to its motor properties, takes a slight but 

 well-defined part in the transmission of sensory impressions, 

 and this idea is based upon experiments which seem to show 

 that slight sensibility remains in the lower extremities after 

 section of the posterior columns. 1 Such experiments, how- 

 ever, must be accepted with a certain degree of reserve, in 

 view of the great difficulty of dividing the columns sepa- 

 rately. If the white substance of the antero-lateral columns 

 take any part in the conduction of sensory impressions, it is 

 slight and unimportant. On the other hand, if the antero- 

 lateral columns of the cord be divided on both sides, the 

 power of voluntary motion is lost absolutely in all parts sup- 

 plied with nerves coming from the cord below the section. 



It would be an interesting point to determine positively 

 the relative importance of the white and the gray substance 

 of the anterior columns in the transmission of motor stimu- 

 lus ; but this has thus far been impossible. We cannot with 

 certainty divide the gray matter of the anterior columns 

 completely and leave the white substance intact, nor can we 

 divide the white substance without injuring the gray. As 

 far as experiments go, however, they seem to show that 



lished. A list of his most important memoirs, with a short account of his ex- 

 periments and conclusions, is given in the Journal de la physiologic, Paris, 1862, 

 tome v., p. 641, et seq. 



1 BROWN-SEQUARD, JErcperimces montrant que les cordons anterieurs de la moelle 

 epinere servent d la transmission des impressions sensitives. Journal de la physi- 



ie, Paris, 1858, tome i., p. 809. 



