ANIMAL DRUGS. 



As the science of medicine has progressed step by step, 

 the great number of drugs derived from the members 

 of the animal kingdom has been reduced. This large 

 number of drugs was gradually introduced during the 

 middle ages, so that in the middle of the sixteenth cen- 

 tury at least 150 drugs derived from some portion of an 

 animal were in constant use. 



In the days of Hippocrates II, 400 B. C, and Dios- 

 corides, 50 A. D., very few such drugs were employed, 

 and at the present time the number is very small, except 

 in the homeopathic Pharmacopoeia, where many of the 

 materials in use during the middle ages have been re- 

 tained. 



Certain animal drugs have maintained their reputation 

 for efficiency, and only a few of these will be considered. 



HIRUDO. THE LEECH. 



This is a worm of the Annelid or Ringed- worm class. 

 The most familiar one of the class is the Hirudo medicin- 

 aliSy and this is the variety most commonly used. It lives 

 in ponds and slow-flowing streams, where it feeds upon the 

 blood of fishes, frogs, snails and other available food 

 materials. It is its habit to take as much at one time 

 as possible, gorging itself upon what supply of food is 

 obtainable. It can thus often live a whole year without 

 feeding twice. Its mode of locomotion is by means of 

 the alternate use of the front and rear suckers, and when 

 disturbed it swims by a rapid wave-like motion of the 

 entire body. 



Description. — The leech usually measures from 5 to 1 5 

 centimeters (2 to 6 inches) in length and is either 



