sriXAL coi;d — heart. 4&7 



functional power of the nerve-centres so quickly in the frog as 

 in warm-blooded animals, it nevertheless does so after a time. 

 In order to discover whether the casca destroyed the power of 

 the spinal cord by acting directly upon it or not, its action upon 

 the heart was investigated, and we found that a short time after 

 its administration it arrested tlie pulsations of that organ. It 

 seemed, therefore, quite possible that the loss of power in the 

 spinal cord was simply due to stoppage of the heart by the 

 poison, but of course tliis was only probability, as the casca 

 might act both on the cord and the heart. We decided this 

 point, however, by administering casca to one frog, and waiting 

 until the heart had stopped. The instant it had done so, we 

 arrested the circulation in a frog of a similar kind and size by a 

 ligature around the large vessels as they arose from the heart. 

 In these two frogs the circulation was equally arrested, but in 

 one of them the poison had been previously carried by the blood 

 to the spinal cord, and could still act upon it although the flow 

 of blood was stopped. If tlie casca had any paralysing action 

 upon the nervous structures of the cord itself, reflex action 

 ought to have ceased in the poisoned frog before doing so in the 

 ligatured frog, but this was not the case. In both frogs reflex 

 action ceased in almost exactly tlie same time. The abolition 

 of the function of the spinal cord is therefore due to stoppage 

 of the circulation caused by the casca, and not to the action 

 of the drug upon the cord itself. The staggering gait, inability 

 to stand, and paralysis which we have observed in dogs and 

 3ats, we attribute, like the paralysis in frogs, to disturbance 

 af the circulation, and not to any special action on the nerve- 

 sentres. 



Action on Clrndation. Action on tlic Heart. — The first action 

 of casca upon the heart of the frog is to cause it to beat more 

 slowly, then the ventricle becomes irregularly contracted, some 

 parts of it being firmly contracted and white, while here and 

 there other points are not contracted, and being filled with 

 blood, look like little red pouches studding the cardiac surface. 

 Finally, the ventricle stops altogether in a state of contraction, 

 while the auricles continue to pulsate for some time longer. 

 In cats also the ventricle sometimes becomes irregularly con- 



2 H 2 



