12 CIECUSrSTANOES MODIFYING THE ACTION OF DRUGS 



tion to his weight, than is the case in animals, and since the 

 spinal cord is larger and ipore highly developed in pro- 

 portion to the brain in animals, it happens that drugs 

 impressing the nervous system exert less effect on the brain, 

 and more on the spinal cord, of animals than they do in man. 

 Thus opium is more powerful in its influence on the 

 brain of man, and strychnin is more potent in its action on » 

 the spinal cord of animals. Drugs are not absorbed so 

 rapidly or perfectly in the enormous digestive apparatus of 

 ruminants as in man; neither do emetics act in these animals, 

 nor in horses; while in none of the lower animals are Agents 

 causing sweating so efficient as in man. 



ACTION OF DRUGS ON HORSES AS COMPARED WITH THAT ON OTHEB 



ANIMALS. 



Differences exist relative to the action of drugs on the 

 horse, as compared with other animals, chiefly in respect 

 to the digestive apparatus. Emetics do not act on the horse, 

 as this animal does not vomit unless the stomach is greatly 

 distended with gas, which causes dilatation of the cardiac 

 outlet. ' Moreover, the stomach is too t>ii.ail to be success- 

 fully compressed by the abdominal walls, and the great 

 length of the oesophagus between the stomach and dia- 

 phragm, together with the horseshoe-like band of fibres at 

 its cardiac extremity, prevent the regurgitation of food. The 

 intestines of the horse, on the other hand, are as volum- 

 inous as the stomach is small, and therefore are powerfully 

 infliieneed by irritants (as purgatives), although the action 

 of cathartics is slow. The bowels of horses excrete vastly 

 more of the fluid ingested than is the case in man or dogs 

 —whose kidneys chiefly assume this function — and these 

 latter organs are said to eliminate about 15 per cent, of the 

 fluid ingesta in the former animals, as against 50 per cent, 

 in man and dogs. 



ACTION OF DRUGS ON RUMINANTS AS COMPARED WITH THAT ON 

 OTHER ANIMALS. 



The capacious four-fold stomach of ruminants always 



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