210 Transactions of the Canadian Institute. [Vol. VII. 



changing the view that usually a markedly slow pulse is an urgent 

 indication for the immediate removal of the anaesthetic. 



As a rule, unless an animal has just been struggling violently, the 

 pulse becomes considerably slowed when he is going under chloroform 

 and becomes fast when he is coming out. The exception mentioned is 

 struggling, and this, as has been already shown, may so hasten the pulse 

 that it only slows when, or just before, the respiration stops. The cause 

 of this slowing is doubtful, some attributing it to stimulation of the 

 vagus by the chloroform vapour, some to the direct poisoning of the 

 heart muscle, and others again to asphyxia. Whatever the cause of 

 this gradual slowing may be, it is a valuable sign clinically. The fall of 

 pressure is evidently not due alone to it, as shown by the fact that such 

 falls occur when the vagi are divided, when atropine is given (vide 

 tracing 47), or while the pulse is still fast after struggling (vide tracing 

 20). Nevertheless the fall in pressure and the slowing of the pulse as a 

 rule go hand in hand in deep chloroform narcosis. 



As regards the effect of posture during chloroform narcosis, generally 

 speaking the animal is rendered less resistant to the effects of gravity 

 than is one not so poisoned, and hence the vertical feet-down position 

 produces a greater fall than it would otherwise do. If the animal be 

 first placed feet-down and then chloroform be pushed, as might be 

 inferred, the pressure falls more freely than when the drug is given in 

 the horizontal position. This is in accordance with Mr. Leonard Hill's 

 observations, when he considers chloroform to be the most powerful 

 agent known for abolishing the mechanisms which compensate for the 

 influence of gravity.^ 



The effects of various operations on the blood pressure while the 

 animal was under chloroform were tried, and as a rule they were 

 chiefly negative. 



Tracing XXIV. — 3/8. — Dog under Chloroform and horizontal. 10 Abdomen opened freely. 11 

 Splenic arterj- tied. 



Tracing 24 is taken from a dog completely anaesthetized with 

 chloroform and lying horizontal. At 10 the abdomen was freely opened 



I Journal of Physiology, Vol. XXI, Nos. 4 and 5, 1897. 



