ABSORPTION OF DRUGS 9 



Salt action is dependent on osmosis. Concentrated salt solutions (hyper- 

 tome) draw water from the tissues and red blood cells; weak salt solu- 

 tions (hypotonic) lose water to the red corpuscles and tissues; salt 

 solutions of the same osmotic tension as the blood (isotonic) and tissues 

 maintain an equilibrium as regards the water content of these. The 

 principle of salt action depends upon the fact that if two solutions are 

 brought in contact through a membrane (or cell wall) they tend to equal- 

 ize in concentration. If cells are placed in dilute salt solution they swell 

 because the solution passes into them until it is of like concentration to 

 the dilute solution outside the cell. If cells are put into a concentrated 

 salt solution they shrink because water passes out until the solutions 

 within and without the cell are of equal strength. The same so-called 

 salt action occurs with most solutions of soluble substances — alkalies, 

 acids and sugar. Catharsis from salts and diuresis are due to salt action. 

 Salt solutions in the bowels absorb water from the tissues and flush them 

 out; salt solutions absorbed into the blood withdraw water from the tis- 

 sues and hydremia of the blood leads to diuresis. Any non-toxic salt 

 (crystalloid) in the blood increases its concentration and leads to a flow 

 of water into it from the surrounding tissues, increases its mass, and 

 pressure, and thus acts as a diuretic. 



No hypothesis can be formulated which will satisfactorily account 

 for the curative action of all medicines in all diseases, and systems of 

 medicine, as allopathy and homeopathy, founded on such hypotheses, are 

 valueless. 



Absorption of Drugs. 

 Drugs are absorbed most rapidly in solution (especially in alcohol) 

 and when the circulation is active. Absorption from the digestive tract 

 is poor when the circulation is depressed or in congested states; also 

 from the subcutaneous tissues in similar conditions, more particularly in 

 edema of these parts. Absorption from the stomach and bowels of 

 healthy animals is chiefly influenced by the quantity of food in them. 

 When these organs are empty, absorption is rapid; but when full, it is 

 slow. For this reason absorption is markedly tardy and imperfect in 

 ruminants. In these animals there is a comparatively impervious skin- 

 like mucous membrane and lack of vascularity in the first three gastric 

 compartments ; while a large amount of food is always to be found in the 

 first and third stomachs; all of which tends to delay absorption and 

 lessen the action of medicines given by the mouth. 



If drugs are irritating, they should be given to animals on the food, 

 or after feeding, in order that they be sufficiently diluted. 



Elimination of Drugs. 



A drug is as much outside the body when within the digestive tube — 

 as far as any action it may have on the body (unless an irritant) — as if 

 it were on the skin. When absorbed, a medicine passes into the blood 

 vessels or lymphatics and thence into the general circulation. That por- 

 tion which enters the portal circulation reaches the liver and may be 

 destroyed in part (some alkaloids) by this organ. After entering the 



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