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 any food. It is usual, however, to make them disgorge the greater part of the blood they have swallowed by sprinkling them with salt; as otherwise they would not bite again till the blood they had taken was fully digested.
Leeches lay eggs, which are covered with a kind of membrane, which serves to protect them when they are deposited in the clay and holes in the sides of ponds. They appear to live on the eggs of fish or frogs, but eagerly attach themselves to the legs of human beings, horses, or cows, whenever they have an opportunity. As there is a prejudice among the country people that Leeches never breed well till they have tasted blood, it is said that they drive their horses and cows into the water inhabited by the Leeches, and consequently that the Leech districts are remarkable for their wretched-looking horses and cattle. Leeches must be five years old before they are fit for medical purposes; and they are caught in shallow water in spring by people going in with naked feet and ankles, to which the Leeches adhere, when they are picked off and put in baskets provided for the purpose. In summer a raft is made of twigs, and the waters being disturbed with a stick, the Leeches rise to the surface, and get entangled in the raft. When caught, they are washed in water with a very little salt in it, and packed in wet linen cloths, which are put into a barrel with a canvas cover, and sent away for sale. London used to be chiefly supplied from the fenny districts of Lincolnshire, but the consumption of these useful worms has been so great that most of our Leeches are now imported through Hambro’ from the east of Europe. Some years since Dr. Pereira stated that the number of Leeches imported by the four principal dealers in London amounted to 7,200,000 annually. They are also, when kept in a glass bottle with water, a good barometer, as they always come up to the neck of the bottle when rainy weather is approaching, remain at the bottom in dry weather, and move anxiously up and down when the weather is stormy. Horse-Leeches are larger than the common species, more voracious, and narrower at each extremity.