PHYSIOLOGICAL EFFECT OF DRUGS 87 



examples of this is in the action of cyanide, iodoacetate 

 and mustard gas on the arterioles of the frog. Mustard 

 gas produces practically no effect at all, HCN produces 

 an almost immediate vasodilation and iodoacetate an 

 almost immediate vasoconstriction. It is no doubt pos- 

 sible by the exercise of sufficient ingenuity, by taking 

 account of the fact that these drugs act at different points 

 upon the metabolism of glucose, to maintain that it is 

 in fact interference with glucose metabolism which is the 

 key point in the attack of all these substances upon cells. 

 But this attitude smacks considerably of special pleading, 

 and a great deal more analysis on the physiological as 

 well as upon the biochemical level must be obtained be- 

 fore it can be accepted. 



Classification of Drugs according to their 

 Physiological Effect 



The possibility exists that some useful principle might 

 emerge from grouping drugs together which produce 

 the same physiological change in cellular behaviour. But 

 it is soon seen that a simple classification along these 

 lines is not very enlightening. As examples we may take 

 the inhibition of muscular contraction, the inhibition of 

 mitosis, and the induction of lachrymation. 



Of course, muscular contraction can in practice be in- 

 hibited by substances which act upon the neuromuscular 

 junction. But as we are here concerned rather with cellu- 



