176 ACTION OF KITPJTB OF AMYL OX THE CIRCULATIOX, ETC. 



small quantities of the drug produce a great effect, and tliat its 

 action speedily passes off, the vapour being either excreted or 

 destroyed in the body. 



In order to avoid the disturbance occasioned by the convul- 

 sions, the animals were then poisoned by curare and the vapour 

 administered. The pressure, as before, sank immediately and 

 did not return to the normal amount so long as the inhalation 

 was continued. It did not, however, sink constantly, and then 

 remain at a definite minimum, but oscillated up and down, just 

 as Traube observed it in curarised animals, and as is shown in 

 the last two curves of Fig. 107. 



It is possible that the convulsions which occur readily in 

 rabbits, but which I have only once, and that to a very slight 

 extent, seen in man, are suffocative, like those produced by CO, 

 for Dr. Gamgee has shown that nitrites acting on the blood 

 prevent haimoglobin from giving up its 0. This is the more 

 probable as the respiration is first affected, and if a drop of 

 nitrite of amyl be mixed with water and the vapour thus 

 diluted be administered, the limbs remain quiet, but the animal 

 begins to make respiratory movements independently of the 

 bellows, and when the vapour is less diluted these become more 

 and more marked till general convulsions take place. 



The diminished blood-pressure might be due either to a 

 lessened power of the heart, or a dilatation of the arteries and 

 a consequently diminished resistance. That the latter is the 

 true cause is rendered probable by the flushing which the 

 vapour causes, both in the human face and the rabbit's ear, and 

 is shown by what might at first seem an anomalous action in 

 some dogs. When the pulse in dogs is slow, the inhalation of 

 amyl produces comparatively little effect on the blood-pressure ; 

 and it might be thought that its action was different in them 

 from rabbits, but the reason is that the pulse, which in rabbits 

 is naturally rapid, and remains unchanged by the vapour, 

 becomes in these dogs remarkably quick, almost as much so as 

 in rabbits. If the vagi be first divided, so that the pulse in the 

 dog becomes quick like that of the rabbit, and the nitrite be 

 then inhaled, the pressure falls just as in rabbits. In order ta 

 confirm this view, and at tlie same tiiae to decide the question. 



