ANATOMY AND PHYSIOLOGY 11 



500 pounds would be half the usual dose for adult horses. 

 In a general way the dose for -all animals from birth to a 

 iew weeks old, is one-twentieth of that suitable for the 

 mature animal of the same species ; for yearlings, about one- 

 third of the adult dose. The dose recommended for dogs 

 is commonly the same as that given to man, but this rule 

 does not apply in the case of some powerful drugs (strych- 

 nine), where the dose should be adjusted to the weight, i.e., 

 so much per pound, live weight. 



It is impossible to calculate the dose for all domestic 

 animals as based on that for animals of one species, be- 

 cause the differences in anatomy and physiology modify the 

 ^actions of drugs in degree and kind, but the dose for sheep 

 is about one-fourth of that for the larger ruminants. 



The repetition of a dose is determined to a consider- 

 able extent by the duration and rapidity of a drug's action. 

 Agents used for their immediate effect, as those relieving 

 pain and stimulating the circulation and respiration, are 

 repeated frequently till the desired effect is attained. 

 Medicines improving the condition of the digestion, blood 

 and nutrition, as tonics of various kinds, require time for 

 the accomplishment of their mission, and are usually given 

 two or three times daily for a period of some weeks. 



Anatomy and Physiology. 



Certain differences in the action of medicines may be 

 observed as occurring in the various species of animals, and 

 in animals as contrasted in this respect with man. 



ACTION OP DRUGS ON ANIMALS AS COMPARED WITH THAT ON MAN. 



From a comparative standpoint the action of drugs on 

 the nervous system of animals differs from that on man. ' 

 This follows according to the " law of dissolution," which 

 teaches that the more highly developed a part of the ner- 

 vous system is in the evolutionary scale, the more sensitive 

 is it to the influence of drugs. Since the cerebrum of man 

 is relatively larger and more highly developed, in propor- 



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