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THE ACTION OF DRUGS 



strophanthus, the chief diuretics, the chief diapho- 

 retics — all these drugs, and a host more, have been 

 studied and learned by experiments on animals. 

 Then comes the answer, that drugs act differently 

 on animals and on men. The few instances, that 

 give a wise air to this foolish answer, were known 

 long ago to everybody : they do not so much as 

 touch the facts of daily practice : — 



" The action of drugs on man differs from that 

 on the lower animals chiefly in respect to the brain, 

 which is so much more greatly developed in man. 

 Where the structure of an organ or tissue is nearly 

 the same in man and in the lower animals, the 

 action of drugs upon it is similar. Thus we find 

 that carbonic oxide, and nitrites, produce similar 

 changes in the blood of frogs, dogs, and man, that 

 curare paralyses the motor nerves, alike in them all, 

 and veratria exerts upon the muscles of each its 

 peculiar stimulant and paralysing action. Where 

 differences exist in the structure of the various 

 organs, we find, as we would naturally expect, differ- 

 ences in their reaction to drugs. Thus the heart of 

 the frog is simpler than that of dogs or men, and 

 less affected by the central nervous system ; we 

 consequently find that while such a drug as digitalis 

 has a somewhat similar action upon the hearts of 

 frogs, dogs, and men, there are certain differences 

 between its effect upon the heart of a frog and on 

 that of mammals. 



" Belladonna offers another example of apparent 

 difference in action— a considerable dose of bella- 

 donna will produce almost no apparent effect upon 

 a rabbit, while a smaller dose in a dog or a man 

 would cause the rapidity of the pulse to be nearly 



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