ABSORPTION AND DISTRIBUTION OF MEDICINES 27 



(Hering). Barium chloride traversed the circulation of a 

 horse in twenty seconds, and injected into the jugular vein of 

 a dog it reached the carotid artery in seven seconds. When 

 the foot of an Albino rat was immersed for a few seconds in 

 chloroform containing one per cent, of atropine, absorption 

 occurred, and dilatation of the pupils followed in from two 

 to five minutes (Waller). 



Medicines may be administered by injection into the sub- 

 cutaneous areolar tissue, the trachea, veins, glands, muscles, 

 rectum, uterus, udder, and large serous cavities ; but the 

 most frequent and generally the most convenient mode of 

 administration is by the mouth, whence, speedily reaching 

 the stomach and small intestine, medicines are absorbed and 

 enter the circulation. Administered in a tolerably con- 

 centrated but soluble form medicines do not generally 

 require to be acted upon by the ferment-containing secre- 

 tions of the digestive canal ; but the digestion of mashes 

 and many restorative foods is promoted by the alkaline 

 saliva, which also favours the hydration and solution ot 

 some drugs. The acid, pepsin-containing, gastric juice 

 dissolves proteids, as well as iron, mercurial and other salts. 

 The alkaline bile emulsifies fats and resins, and activates 

 some agents, such as aloes ; the pancreatic fluid furthers 

 digestion of starch, albumin and fats ; and specially refrac- 

 tory substances are more thoroughly reduced by the alkaline 

 intestinal juices. Medicines taken up by the vessels of the 

 gastro-intestinal mucous membrane are conveyed to the 

 liver where they may be stored up, detained for a time, 

 neutralised or modified, eliminated in the bile, or passed 

 unchanged into the general circulation. 



Absorption by the healthy buccal membrane is possible, 

 but, excepting the most volatile agents, such as prussic acid, 

 medicines introduced into the mouth are either quickly 

 swallowed or rejected, and consequently contact with its 

 thick epithelium is too brief to permit of penetration. 

 Gastric absorption varies with the species, the age of the 

 animal, and the state of the stomach as regards contents, 

 digestive phenomena, and freedom from disease. Very 

 active in dogs and pigs, gastric absorption in cattle and sheep 

 occurs only in the abomasum. In horses, absorption by 



