THE RINGED WORMS OR ANNELIDS 121 



The body of a leech is generally flattened and provided 

 with a sucker at each end by means of which it adheres 

 to various objects. Leeches crawl by a looping motion. 

 Some species are furnished with teeth, especially those 

 which live by sucking the blood of higher animals. Of 

 the "blood suckers" the common medicinal leech is best 

 known, since it was long used for bleeding patients, and 

 was extensively raised in swamps and ponds especially 

 prepared for leech culture. After a full meal of blood, a 

 medicinal leech may live several months without food. 

 Some species of leech attack small animals such as worms 

 and snails; others, and especially the few that live in the 

 sea, live upon the bodies of fish, and in the tropics there 

 are land leeches which are troublesome pests to animals 

 and man. 



