HIRUDO MEDICINALIS. M3 



considerable velocity. Tn winter they resort to deep water, or 

 bury themselves to a considerable depth in the mud leaving a small 

 aperture to their subterraneous habitation. Dr. J. R, Johnson, 

 of Bristol, who has written an excellent Treatise on the " Medical 

 and Natural History of the Leech," says they begin to make their 

 appearance in the water about the end of March or the beginning 

 of April. During sunny weather they may be seen very actively 

 swimming from place to place ; but should the weather prove cold 

 or cloudy they confine themselves to the mud. In rainy or windy 

 weather, when the water is agitated, they retire from sight. Just 

 before a thunder-storm, they commonly come up to the surface ; 

 and this the leech-gatherers find a good opportunity for collecting 

 them. Formerly Norfolk used to supply a great part of the leeches 

 which are brought to the London market, but at present they are 

 imported chiefly from Hamburgh, Bordeaux, and Lisbon. They 

 are caught in spring and autumn by people who wade into the 

 ponds and allow them to fasten on their legs ; or by beating the 

 water with poles, which causes the leeches to rise to the surface, 

 when they are taken with the hand and put into bags. They are 

 best preserved in jars half filled with pure water, which must be 

 frequently renewed, and kept in a cool place. But previously 

 to placing the Leeches in this vessel they should be singly 

 examined. If, on being handled, they contract, and feel hard and 

 firm, it affords the best indication of their being healthy; but should 

 they feel flabby, or exhibit protuberances or white ulcerous specks 

 on their surface, they should be kept in jars by themselves. 



The food of the Medicinal Leech appears to consist of the blood 

 of quadrupeds and other animals, which they casually meet with in 

 the water, and which, as they are capable of an abstinence of 

 several weeks or even months, they generally find in great abun- 

 dance. Should it prove otherwise, they arc said to subsist by suck- 

 ing the fluids of fish, frogs, worms, and the larvse of aquatic 

 insects. 



Leeches appear to have been employed for blood-letting for more 

 than two thousand years. We learn from Galen, that the medical 

 utility of leeches was known to Hippocrates : in inflammation of 

 the liver, they were preferred by Aretceus to cupping-glasses ; and 



