12 CIRCUMSTANCES MODIFYING THE ACTION OF DRUGS 



Outlet. Otherwise the stomach is too small 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 

 influenced 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 

 contains large amounts of food in the rumen and abomasm, 

 while the impervious, poorly vascular and skin-like gastric 

 mucous membrane renders absorption feeble and imperfect 

 and enforces a comparatively larger dosage than is proper 

 for horses of greater weight. Ruminants are also generally 

 insusceptible to emetics. The skin and kidneys of rumi- 

 nants are still less active than is the case in horses. 



ACTION OF DRUGS ON DOGS AND PIGS AS COMPARED WITH THAT ON 

 OTHER ANIMALS. 



The action of medicine on dogs and pigs is similar in 

 kind to that observed in man, but the former animals are less 

 sensitive to drugs as a rule, since the dose suitable for a 

 man weighing 150 pounds is appropriate for a dog of 40 

 pounds weight. As exceptions to this rule, we find that dogs 

 will not bear the human dose of calomel, oil of turpentine, 

 or strychnine. In fact, the ordinary tonic dose of strych- 

 nine (gr. gip) for man will throw a medium-sized dog into 

 convulsions, and may kill a small animal, notwithstand- 



