ABSOEPTIOiSr OF DRUGS 3 



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 otheirs may imme- 

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

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

 possible to determine whether medicines affect the cells 

 of an organ or nerve-endings in the organ. The action of 

 most vegetable drugs is thought to arise f-rom the chemical 

 affinity of their active principles for the part or parts acted 

 upon. 



Thus the selective action of strychnine depends upon its 

 forming a chemical compound with the protoplasm of the 

 cells of the spinal cord. The action of many of the inorganic 

 salts on the body is due to their physical properties, as dif- 

 fusion and osmosis (see " salt action " under sodium chlo- 

 ride, and action of sodium sulphate on bowels). Also the 

 action of most salts is owing to their being in great part 

 dissociated in the weak solutions found in the tissues into 

 electrically positive (kation) and negative (anion) ions. 

 The action of a salt is then usually the action of its ions and 

 not of its molecule. Neither does the action of an ion repre- 

 sent the chemical action of the atom, as when KCl is disso- 

 ciated into a positive K ion and a negative CI ion. The 

 action of the ion is a physical or electrical action. Some- 

 times one ion is inert, as the CI ion in KCl. Sometimes one 

 is inert and the other very toxic, as in IvCN^, where the posi- 

 tive or K ion is practically without action (see action of 

 ions under " Special Salts"). 



'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 homceo- 

 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 wjien the circulation is de- 

 pressed or in congested states; also from the subcutaneous 

 tissues in similar conditions,, more particularly in cedema 



Digitized by Microsoft® 



