778 ARTICULATA—LEECH. 
able. The house leech,! which is the largest of all, and grows te fsur 
inches in length, with a glossy black surface, is of no use, as it wili not 
stick to the skin; the snail leech is but an inch in length; ard 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? 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 animai 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. Itis 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 thesun. 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 confines — 
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 homy jaws; no eyes; anus superior, near th¢ 
posterior disc. 
® Mirudo mediciralis, Lin. 
