142 HIRUDO MEDICINALIS. 



that the leech is oviparous. He says, " In the month of May I 

 have, from large leeches, seen protruding from the female organ of 

 generation, a white opake oval substance, having a considerable 

 quantity of mucus adhering to it, which I cannot conceive to be 

 excrementitious, but rather an ovum." That this was the real fact 

 there can now be no doubt, since the observations of Mr. Hebb 

 have since been amply confirmed by M. Virey, author of a paper 

 in one of the early volumes of the Journal de Physique, and 

 by Dr. Noble, resident physician at Versailles. The ova or 

 rudiments of the future Leech, are imbedded in a gelatinous 

 mass, and contained in a bag of a spongy texture, somewhat 

 resembling in size and figure the cocoon of the silk-worm. The 

 ova are deposited on, or agglutinated to, aquatic plants, and are 

 hatched by the heat of the sun. M. Planchy, in a Memoir read 

 before the Society of Agriculture and the Arts, in the department 

 of the Seine, asserts that the existence of the cocoons of the Leech 

 has been for a long time known in the department of Finistere. 

 According to this gentleman, it is by means of these cocoons, the 

 leech-dealers of Bretagne, and particularly of Finistere, replenished 

 with Leeches the ponds destined to furnish the metropolis with a 

 great portion of the leeches there employed. About the month of 

 April or May, according to the nature of the season, they send out 

 labourers, provided with spades and baskets, to the ponds and 

 marshes, where they are known to exist in abundance. These 

 workmen then set about removing those portions of mud that 

 are known to contain cocoons, and which are afterwards depo- 

 sited in sheets of water previously prepared for their reception. 

 Here the young leeches are allowed to quit them, but are, after an 

 interval of six months, withdrawn, for the purpose of being con- 

 veyed to larger ponds. Horses and cows are then driven in to feed 

 on the margin of these ponds, with the view of affording the 

 leeches nourishment and accelerating their growth ; and in twelve 

 months from this period the leech-dealers begin to collect them for 

 medical use. 



Leeches do not cast -their skin ; but at certain times throw off a 

 tough slimy substance from their bodies, apparently the production 

 of disease. They swim in a serpentine direction, and at times with 



