Section IV., 1914 1267] Trans. R.S.C. 



Some Observations on Vaso-motor Reflexes. 



By Swale Vincent and A. T. Cameron. 



(From the Physiological Laboratory, University of Manitoba, 

 Winnipeg.) 



(Read May 27, 1914.) 



The present investigation was suggested by the conflicting results 

 obtained by our senior class of students in trying to obtain the results 

 described in the majority of text-books on stimulation of the central 

 end of an afferent nerve, and by what seemed to us an inexplicable 

 contradiction frequently met with, between the effect of stimulating 

 the cut central end of a sensory nerve, and the effect of stimulating the 

 terminals of such a nerve, as for example, in the skin. 



Insufficient attention has been paid by previous investigators 

 to the specific pharmacodynamic effect of the anaesthetic employed. 

 It seems to have been assumed by most workers that a standard 

 condition of the animal should be aimed at, in which disturbing in- 

 fluences due to reflex muscular spasms and reflex respiratory move- 

 ments were as far as possible eliminated. Such an object is undoubt- 

 edly desirable from many standpoints, but has in our opinion the 

 supreme disadvantage that the specific action of the anaesthetics 

 concerned is disregarded. In experiments with dogs the majority 

 of observers seem to have employed ether as an initial anaesthetic 

 followed by morphia, and frequently curare. We have found no de- 

 tailed account of what happens in the record of the vaso-motor re- 

 flexes if the animal be simply anaesthetised with ether. We have 

 considered that this problem should not be shirked, especially as 

 such a condition is one very frequently met with in surgical procedure 

 upon the human subject. 



The problem of the vaso-motor reflexes is of course intimately 

 connected with that of shock, but with the latter subject itself we do 

 not propose to deal. 



From a large number of experiments on dogs, cats, and rabbits 

 we are led to the following conclusions: 



When an animal is deeply under the influence of ether, it is fre- 

 quently impossible to obtain any vaso-motor reflexes whatever. When 

 anaesthesia is fairly complete the effect of stimulating the central end 

 of the cut sciatic nerve is sometimes a distinct rise. As the effect of 

 the anaesthetic begins to pass off, the rise is followed by a more or less 



