ABSORPTION OF DRUGS 6 



vous system. Some drugs, however, may directly influence 

 muscular tissue, as is seen in the supposed action of digitalis 

 on the nerve-free heart's apex; while others may imme- 

 diately act on the cells of an organ, as pilocarpine on 

 the sweat glands. As in the latter instance, it is usually im- 

 possible to determine whether medicines affect the cells 

 of an organ or nerve-endiugs in the organ. Our knowledge 

 of the curative action of medicines is chiefly derived from 

 clinical experience, or deduced from the effects of drugs on 

 healthy animals. It is, however, sometimes possible to 

 foretell to a certain extent the action of a synthetic com- 

 pound from its chemical composition. When our knowledge 

 of the action of drugs on healthy animals is applied to 

 remedy known pathological conditions (e.^., the use of 

 astringents to stop bleeding by their action in contracting 

 vessels and clotting blood), we are practising rational thera- 

 peutics. 



No hypothesis can be formulated which will satisfac- 

 torily account for the curative action of all medicines in all 

 diseases and systems of medicine, as allopathy and homoeo- 

 pathy 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 wTien the circulation is de- 

 pressed or in congested states ; also from the subcutaneous 

 tissues in similar conditions, more particularly in oedema 

 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 



