SANGUISUGA. 



legs. In summer, when they have retired to deeper waters, a 

 sort of raft is constructed of twigs and rushes, by which a few 

 are entangled. They are also taken by laying baits of liver, 

 to which the leeches resort and are then caught ; but this last 

 method is thought to make them sickly. A leech may be 

 known to be in good health if it be active in the water and 

 plump when taken out. The most certain method of indu- 

 cing leeches to bite is to cleanse the skin thoroughly ; and they 

 should be exposed to the air for a short time previous to their 

 application, as by this means they will bite more freely. If 

 they are voracious, they may be applied to the part by being 

 held lightly in the fingers, or they may be placed in a leech- 

 glass, which is a preferable mode. They should not be dis- 

 turbed whilst sucking, nor the patient be exposed to too great 

 warmth, or they will fall off; this they should always be per- 

 mitted to do of their own accord. When the feech has 

 dropped off, it should be seized by the tail and drawn between 

 the finger and the thumb so as to cause it to disgorge most of 

 the blood ; or this may be effected by putting it into a weak 

 solution of common salt. It should then be placed in many 

 successive fresh waters, and if not injured, it may be used 

 again at a future time. 



The corium, or true skin, which displays the rings of which 

 the body of the leech is composed, seems to be semi-cartilagi- 

 nous, and capable of expansion to nearly three times their nat- 

 ural magnitude ; hence the quantity of blood which the leech 

 can draw is greatly disproportionate to its natural size. Mr. 

 Kennedy has stated, on the authority of experiment, that it is 

 equivalent to the weight of the animal. M. Moquin Tandon 

 affirms that a small lively leech will take twice its weight, 

 a middle-sized one one half its weight, and a large one its 

 weight. Derheim says six times its weight. The average, 

 however, is considered about two drachms. This, neverthe- 

 less, is no criterion of what is obtained ; for the blood contin- 

 ues to flow after the leech falls off, and by applying a poul- 

 tice or warm water to the orifices, or a cupping-glass over the 

 place, a considerable quantity may be afterwards abstracted. 



There are some circumstances connected with the applica- 

 tion of leeches that require to be noticed. An erysipelatous 

 inflammation sometimes follows their application, which has 

 been referred to a peculiar irritable state of the skin of the 

 patient, but which has been ascertained by M. Derheim to 



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