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, (Sanyuisuga 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 



