540 Articulated Animals. 
nuisance by gardeners, Earth Worms perforate, and 
loosen the soil, and render it pervious to rains and the 
fibres of plants, by drawing into it straws and the stalks 
of leaves: and chiefly by throwing infinite numbers of 
lumps called worm-casts, which form a fine manure for 
grass and corn. They are, however, very injurious to 
plants in pots. 
THE LEECH, (Sanguisuga officinalis,) 
Is about three inches in length, and in its exterior form 
somewhat resembles the worm, when extended, but 
often contracts itself greatly in length, at the same time 
expanding in thickness. It has a small head, a black 
skin, with six yellow lines above, and spotted with 
yellow below. The mouth of the Leech is of curious 
construction ; it has three jaws, each of which is armed 
with two ranges of very fine teeth, with which it pierces 
the skin ; and then draws up, as through a siphon, the 
•blood, upon which it feeds. The progressive movement 
of the Leech is effected by sticking, by suction, its 
mouth to a certain spot, then bringing its tail, which 
also has the property of sticking, in the same manner 
as the head, and then advancing its head further on, 
quickly followed by the tail, and so on. The common 
Leech is very often met with in brooks and rivulets. 
Its uses in medicine are well known, as by its means 
the blood can be extracted from diseased parts, to which 
the lancet cannot be applied. 
The blood which the Leech sucks out of the wound 
it makes supplies it with nutriment for so great a 
period of time, that a Leech, after having been satisfied 
with blood, has been known to live three years without 
