488 MESSRS. F. GOTCH AND V. HORSLEY 



We reserve also to the end of this chapter the pertinent bearing of these observations 

 upon the important doctrine of kinaesthesis (BASTIAN). 



The evidence of the passage of nerve impulses, as indicated by electrical changes, 

 from the aroused centres in the cord down the afferent (sensory) fibres of the posterior 

 roots may be grouped as follows : 



(1.) Electrical changes in the posterior roots and mixed nerve with all anterior roots 

 cut when the spinal centres discharge under the influence of strychnia. 



(2.) Electrical changes in the above structures when the spinal centres are discharged 

 reflexly. 



(3.) Electrical changes in the above structures when the spinal centres are aroused 

 by electrical excitation of the columns of the cord. 



(1.) The Electrical Changes in the Posterior Roots when the Spinal Centres are Excited 

 by Strychnia. 



The most remarkable illustrations of the fact that impulses emerge from a dis- 

 charging spinal centre on its afferent as well as its efferent side, is that furnished by 

 the following experiments. 



In a Cat (211) the cord was divided as usual in the lower dorsal region (llth 

 dorsal) and both sciatic nerves exposed and divided. The central end of each nerve 

 was connected when desired with the galvanometer. The cauda equina was then 

 exposed, and the posterior roots of the 5th, 6th and 7th lumbar nerves, and those of 

 the 1st and 2nd sacral, were divided on the right side, whilst the anterior roots of 

 the same nerves were divided on the left side. 



The right nerve was thus in connection with the cord by its anterior roots only, 

 the left by its posterior. Thirty minims of a 1 per cent, solution of acetate of 

 strychnia was now injected intraperitoneally. When the tetanic strychnia spasms 

 commenced, excitatory electrical effects were observed in both nerves. 



The amount of the deflections varied with the intensity and direction of the spasms, 

 but were always larger in the right nerve (posterior roots cut) than in the left, averaging 

 180 in the right, and 30 in the left. The effect, though smaller in the posterior 

 root, was absolutely definite in character, each spasm being accompanied by an effect. 



In another animal, Cat (341), we divided the cord at the 12th dorsal vertebra and 

 exposed the cauda equina. We then selected the 7th left lumbar posterior root, 

 divided it near the ganglion and connected in accordance with our method the 

 central end with the galvanometer. 



Thirty minims of a 1 per cent, solution of acetate of strychnia were then injected 

 into the peritoneal cavity. Each strychnia spasm caused excitatory electrical effects in 

 the posterior root, which gradually increased in amount in proportion as the discharges 

 became more violent and prolonged. The galvanometer deflections, which were very 

 definite in character and similar in direction to those obtained by the passage of nerve 

 impulses, amounted to 40 at first, then 70, and finally 120. 



