778 ARTICULATA — LEECH. 



able. The horse leech. 1 which is the largest of all, and grows to four 

 inches in length, with a glossy black surface, is of no use, as it will not 

 stick to the skin; the snail leech is hut an inch in length; and though it 

 will stick, is not large enough to extract a sufficient quantity of blood from 

 the patient ; the broad-tailed leech, which grows to an inch and a half in 

 length, with the back raised into a sort of a ridge, "will stick but on very 

 few occasions; it is the large brown leech 2 with a whitish belly, that is 

 made use of in medicine, and whose history best merits our curiosity. 



The leech has the general figure of a worm, and is about as long as one's 

 middle finger. Its skin is composed of rings, by means of which it is pos- 

 sessed of its agility, and swims in water. It contracts itself when out of 

 water, in such a manner that, when touched, it is not above an inch long. 

 It has a small head, and a black skin, edged with a yellow line on each 

 side, with some yellowish spots on the back. The belly also, which is of a 

 reddish color, is marked with whitish yellow spots. But the most remarka- 

 ble part of this animal is the mouth, which is composed of two lips, that 

 take whatever form the insect finds convenient. When at rest, the opening 

 is usually triangular ; and within it are placed three very sharp teeth, capa- 

 ble of piercing not only the human skin, but also that of a horse or an ox. 

 Still deeper in the head is discovered the tongue, which is composed of a 

 strong fleshy substance, and which serves to assist the animal in sucking, 

 when it has inflicted its triple wound ; for no sooner is this voracious crea- 

 ture applied to the skin, than it buries its teeth therein, then closes its lips 

 round the wound which it has made ; and thus, in the manner of a cupping- 

 glass, extracts the blood as it flows to the different orifices. 



The leech is viviparous, and produces its young one after the other, to the 

 number of forty or fifty at a birth. It is probable that, like the snail, each 

 insect contains the two sexes, and that it impregnates, and is impregnated, 

 in the same manner. The young ones are chiefly found, in the month of 

 July, in shallow running waters, and particularly where they are tepified by 

 the rays of the sun. The large ones are chiefly sought after ; and, being put 

 into a glass vessel filled with water, they remain for months, nay, for years, 

 without taking any other subsistence. But they never breed in this confine- 

 ment ; and, consequently, what regards that part of their history still 

 remains obscure. 



In England, they seldom grow to above four inches ; but in the East, 

 they are found from six to seven. Their pools abound with them in such 

 numbers, that it would be dangerous bathing there, if from no other consi- 



1 Hirudo sanguisuga, Lin. The genus Hirudo has the body oblong, blunt, slightly 

 depressed, widened posteriorly, composed of numerous contractile segments, and with the 

 posterior extremity terminated by a broad prehensile disc; mouth naked, dilatable 

 armed interiorly with three teeth or horny jaws ; no eyes ; anus superior, near ibo 

 posterior disc. 



• H'rudo mediciialis, Lin. 



