THE MEDICIXAL LEECH. 481 



small part of the northern coast of Africa. In some of these relatively 

 confined regions it has heen exterminated. The demand for it has 

 become very great ; France and Germany, for example, use about 

 thirty million, and the exportation from Hamburg alone has been 

 thirty million in a year.* It is not surprising that so important a 

 demand has raised the price of leeches till they have become a very 

 profitable article of trade. 



The successful stocking of a pond with leeches is a work requiring 

 considerable care ; the animal has many enemies, against which it must 

 be protected, and will not thrive except under specially favorable con- 

 ditions. The mother-leeches, when planted in the pond, lay their 

 cocoons (which contain the eggs) as in nature, and the young brood is 

 hatched out at the proper time ; but this brood, besides protection, 

 requires its natural food, sickens if it does not find it, and can not be 

 fed artificially. The young worms will not thrive in artificial ponds ; 

 neither can they be transplanted from other countries and left to 

 themselves without having first undergone a process of acclimatization. 

 The most suitable ponds for acclimatizing leeches should be dug in 

 bog-lands to a depth of about six feet, and should have from about 

 six to ten inches of bog-soil on the bottom. The pond should contain 

 about three feet of water, and should be provided with an inflow of 

 fresh water and be surrounded with a wall two or three feet high. 

 If the leeches are put in the pond in May or June, they will deposit 

 their cocoons toward September in funnel-shaped holes in the peaty 

 bottom ; in the course of a few days some ten or fifteen young 



Fro.. 3. 8. The iaw, with its saw-liketooth-plat.es. 9. The head, with its three-parted month open- 

 ing. 10. The upper side of the head, with ten eyes. 11. Section of a cocoon with its eggs. 



leeches will come out from the cocoon, and will attach themselves to 

 the old one to suck from it till they are large enough to seek food for 

 themselves. For food, the pond should be furnished with calamus and 

 other reed-like plants ; and duck-weed, little fishes, snails and frogs 

 should be put into it. Toward the latter part of the fall the animals 



* Although the application of leeches has been diminished in consequence of the adop- 

 tion of new practices in medicine, which permit bloodletting only in a limited degree, the 

 use of the animal is still considerable, and always will be so. A few years ago, when 

 bloodletting played an important part in sickness, leeches enough could not be got, and 

 it was hard to satisfy the demand in the ordinary way. Five to six million leeches, cost- 

 ing a million and a half of francs, were used in the hospitals of Paris yearly from 1829 

 to 1836, and 187,000 pounds of blood were drawn annually, or 1,496,000 pounds in the 

 eight years ! 



vol. xvn. 31 



