Hirudo, B.P. Leeches. Hirudo Australis, I.C.A.
Other tomes: Sayre
Leeches are fresh-water annelids, the speckled leech, Sanguisuga medicinalis, Savigny, and the green leech, Sanguisuga officinalis, Savigny (Class Hirudinea), being obtained chiefly from Germany (near Hanover) and the South of France. They have a soft, smooth body, about 5 centimetres in length, tapering towards the extremities, both of which are provided with disc-shaped suckers. The anterior sucker is the smaller, and surrounds the tri-radiate jaws, by which the leech effects an incision in the skin. The dorsal surface is olive-green, with six rusty-red longitudinal lines; the ventral surface of the speckled leech is greenish-yellow, with black spots, that of the green leech being olive-green, with a black line. The buccal secretion of leeches contains a substance named hirudin, which retards the coagulation of blood. It is extracted by treating the minced heads of leeches with physiological salt solution, at a temperature of 38° to 40°, and can be obtained in brownish lamellae or light masses. It is readily soluble in water, but insoluble in alcohol or ether.
Uses.—Leeches are used to reduce congestion and inflammation in such conditions as pleurisy, pneumonia, ophthalmia, pericarditis, inflammation of the car, liver, etc. Each leech draws on an average about 6 mils (90 minims) of blood. The blood drawn does not coagulate, owing to its admixture with the pharyngeal or buccal secretion of the leech, which contains the active substance hirudin, which checks its coagulability. This secretion is also injected into the place bitten, and is in some degree the cause of the persistent haemorrhage that often follows removal of the leech, as well as of the apparent bruising round the site of the puncture. If desired, the bleeding may be encouraged to persist by hot fomentations or poultices. The haemorrhage may usually be arrested by the pressure of a pad of cotton, fixed by a bandage; or a solution of ferric chloride on cotton may be used as a styptic. Leeches are usually applied with a leech glass; or a hole may be cut in a piece of blotting-paper, and the leech confined to its position by a pill-box or tumbler. The skin should be cleansed and moistened with sweetened milk at the site of application. If hirudin be injected into the general circulation the blood drawn off takes several hours to clot. It has, therefore, been suggested that this substance should be given to those suffering from thrombosis, and in other conditions in which the blood is apt to clot too readily.
HIRUDO AUSTRALIS, I.C.A.
Australian or five-striped leeches, Hirudo quinquestriata, Schmarda (Class Hirudinea), are found in the Australasian Colonies, where they are used instead of the European varieties. They are also known as Hirudo Australis, Bosisto, or Limnobdella quinquestriata, R. Blanch. They are greenish-yellow on the ventral surface, and yellowish-brown on the dorsal surface, which is also marked with live longitudinal stripes. The jaws are large and contain forty-eight to fifty teeth, the inner ones being the larger.
Uses.—Australian leeches are used in a similar way to European leeches, and for the same purposes (see Hirudo).