248 Dr. W. P. May. On the Seymental Representation 



A further important condition of the particular function with which 

 we are now concerned (sensori- motor reflex) is that, from the present 

 investigation, it seems certain that the path along which the im- 

 pulses pass as evidenced by movement elicited in stimulating a 

 certain posterior root, is directed towards a point below the level of 

 that posterior root, and, not as we might suppose, chiefly in the same 

 segment, or even above the level at which the posterior root joins the 

 cord. 



The proof of this new conclusion is afforded by many facts given in 

 the paper, not the least interesting of which is, that on direct stimu- 

 lation of the second or third anterior lumbar roots in the dog, no 

 movement results in the lower limb, yet stimulation of the third 

 posterior lumbar root gives distinct flexion and adduction of the hip 

 and flexion of the knee, and stimulation of the second posterior 

 lumbar root gives slight flexion of the hip and knee. In this con- 

 nexion also results obtained by Claude Bernard, Schiiltze, Ramon-y- 

 Cajal, Kolliker, Betzius, and Grolgi afford similar evidence. 



Influence of the Posterior Roots upon the Nerve Centres in the Spinal 



Cord. 



It was found that repeated excitation of the posterior roots de- 

 cidedly increased the excitability of the posterior roots themselves, 

 of the spinal cord and of the anterior roots. The difference in the 

 excitability of the preparation before and after the previous stimula- 

 tion may be represented by the fact that, whereas the minimal 

 stimulus before the application of the repeated stimulus was repre- 

 sented by a distance of 50 cm. of the secondary from the primary coil 

 in the condition of heightened excitability, a minimal stimulus was 

 obtained at a distance -of 70 cm. On the other hand, by cooling the 

 posterior roots as suggested by Professor Gad, a converse effect was 

 produced. The results of Belmonda and Oddi are also quoted in this 

 connexion. 



Results of Experiments upon the Spinal Cord in the Monkey. 



Method. The same as above. 



The same general results were obtained by stimulation of the 

 spinal cord in the monkey as described in the case of the 

 dog. The area found excitable was the postero-external column, 

 stimulation of which from the thirteenth dorsal segment to the 

 second sacral segment inclusive produced after a very short latent 

 period lateral flexion of the spinal column, flexion and adduction of 

 the hip, flexion of the knee, ankle, and toes, movement of the 

 tail and perinceum, and peristalsis (rumbling of the bowels), though 

 it depended on the position of the electrode and the strength 



