PRELIMINARY CONSIDERATIONS. 

 Definitions. 



Pharmacology is derived from the Greek, pharmakos, a drug, and is 

 the sum of all exact knowledge pertaining to drugs, and therefore em- 

 braces materia medica, therapeutics, pharmacy, and pharmacology in its 

 more recent and limited interpretation. 



Materia Medica, derived from two Latin words signifying medical 

 materials, treats of the derivation, natural history, physical and chemical 

 properties, physiological actions, doses, and tests of purity of drugs. A 

 special term sometimes used to describe the physical and chemical prop- 

 erties of drugs is pharmacognosy, while pharmacodynamics, or pharma- 

 cology (in a limited sense), refers to the action of drugs on healthy 

 animals. 



Therapeutics, derived from the Greek, therapevo, meaning to serve 

 or attend the sick, is that branch of knowledge which treats of the appli- 

 cation of all means — ^medicinal or otherwise — to the cure of disease or 

 relief of pain. The term has been further subdivided as follows: 

 Rational Therapeutics, which treats of the application of drugs as 

 founded on their physiological actions; Empirical Therapeutics; the use 

 of drugs as based on clinical evidence ; and General Therapeutics, the use 

 of remedial agents other than drugs, e. g., heat, cold, electricity, food, 

 etc. 



Pharmacy is the art of preparing, compounding, dispensing and pre- 

 serving drugs. 



Metrology, the science of weights and measures. 



Toxicology, derived from the Greek toxikon, a poison, is that branch 

 of knowledge which treats of the nature, actions, detection and treatment 

 of poisons. 



A medicine is an agent of animal, vegetable or mineral origin used 

 for the cure of disease or relief of pain. The word cure, signifies literally 

 to care for, from the Latin euro, and did not in its original sense mean 

 to restore to health, although that is its present interpretation. 



A drug, derived from the Dutch, droog, meaning dry, is now used 

 synonymously with medicine, although originally referring to an herb or 

 dried medicinal plant. 



Mode of Action of Drugs. 



Drugs act locally when they influence a part with which they come 

 in contact, and also when they affect one organ or apparatus after ab- 

 sorption. The first meaning is the usual one. 



Drugs act generally when they impress the body as a whole after 

 absorption. Drugs applied to the unbroken skin usually act locally be- 

 cause they are commonly unabsorbed; also when drugs insoluble in the 

 digestive tract (as charcoal and chalk), are given internally they act 

 locally for the same reason. The local action of drugs after absorption 

 is sometimes known as selective action, i. e., the power that most drugs 



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