ACTIONS OF MEDICINES ON DOGS AND PIGS 35 



exceptions. Dogs, for instance, take six or eight times the 

 dose of aloes usually given to human patients, but are 

 seriously injured by half as much calomel or oil of turpentine 

 as is prescribed for a man. The opinion generally held, 

 that medicines may be given to dogs in the same doses as 

 to man, cannot therefore be safely entertained without many 

 reservations. In dogs, while the stomach is relatively large, 

 the alimentary canal is short and straight, and purgatives 

 consequently act with greater rapidity than in other veterin- 

 ary patients. Another peculiarity is the facility with which 

 they can be made to vomit. Indeed, vomition in dogs is 

 often produced by their eating various grasses, by their 

 swallowing nauseous or unpalatable matters, or by their 

 overloading the stomach. The kidneys are excited with 

 more difficulty than in horses or cattle. On Pigs the actions 

 of medicines are similar to their actions on men and dogs. 



Sir Lauder Brunton points out several curious differences 

 in the actions of drugs on several of the lower animals. 

 Morphine convulses frogs, but, even in large doses, has no 

 effect on pigeons, except in reducing their temperature. 

 Belladonna quickens cardiac action in man, dogs, and 

 horses, by paralysing the vagus, which controls or restrains 

 heart action. But in rabbits the vagus has hardly any 

 appreciable effect in regulating the heart-beats, and these 

 animals accordingly take large doses without having the 

 rapidity of the circulation increased. The rabbit's heart 

 not being controlled by the vagus, a marked difference also 

 occurs in the action of amyl-nitrite on rabbits as compared 

 with dogs. Such observations are not only most interesting 

 in themselves, but greatly further the understanding of 

 the actions of drugs. 



The action of medicines is influenced by the age of the 

 patient, and as a rule very young animals are more sus- 

 ceptible than adult animals. Young dogs are much more 

 easily affected by morphine than adult dogs. Kittens, 

 however, seem to be able to withstand larger doses of 

 morphine than fully grown cats (Guinard). The young 

 tolerate chloroform anaesthesia better than the old, and 

 poisons such as strychnine and digitalis may be given in 

 larger doses to young animals than to adults, 



