32 ACTION DIFFERENT ON DIFFERENT ANIMALS 



In a variable but usually short period, medicines, generally 

 in a modified form, are eliminated by the bowels, kidneys, 

 skin, salivary and mammary glands, or pulmonary mucous 

 membrane. Digitalis, for example, after exerting its action 

 mainly on the heart and arterioles, is removed by the kid- 

 neys. Alcohol and its analogues are got rid of by the skin 

 and kidneys, and also pass away through the respiratory 

 mucous membrane. During their excretion medicines exert 

 their in-contact effects on the excretory organ and passages. 

 Thus, aloes and neutral salts, after stimulating the secretion 

 and movements of the bowels, are in part absorbed into 

 the blood, and thence are returned into the bowels, causing 

 further purgation. Nitre, and small doses of salines and 

 ethers, chiefly removed through the kidneys, produce 

 diuresis. Terebene and various balsams during their ex- 

 cretion by the pulmonary membrane or urinary passages 

 exert their antiseptic properties. 



III. The several species of veterinary patients are differ- 

 ently affected by many medicines. These differences, how- 

 ever, are in degree rather than in kind, and depend upon 

 differences in organisation and function. On the circu- 

 latory, respiratory, and urinary systems, which nearly 

 resemble each other in man and the domestic animals, 

 medicines act tolerably uniformly. Thus, aconite, digitalis, 

 and nitre, produce very similar effects in men, horses, dogs, 

 and cattle. Greater diversity, however, occurs in regard to 

 medicines acting on the nervous, digestive, and cutaneous 

 systems, which differ considerably in the several species of 

 animals. Rabbits and monkeys seem to possess a special 

 resistance to the action of atropine. Apomorphine, which 

 promptly causes vomiting in dogs, has no emetic action on 

 the pig (Feser). Morphine is an excellent hypnotic for the 

 dog ; but in the cat and pig it causes excitement and con- 

 vulsions. 



The more highly any organ or system of organs is developed 

 the more susceptible does it become to the action of medi- 

 cines, and, it may be added, to diseases also. This general 

 law explains why the highly-developed human brain is 

 specially susceptible to the effects of such cerebral medi- 

 cines as opium and chloral, and why frogs, whose spinal 



