Dispensatory of the United States, 161 



or rings, breathing generally by means of branchiae, with a nervous 

 system consisting in a double knotted cord, destitute of feet, and 

 supplying their place by the contractile power of their segments or 

 rings. The third order of this class, Abranchiatce, comprehends 

 those worms which have no apparent external organ of respiration. 

 This order is again divided into two families, to the second of which, 

 the Asetigera, or those not having setas to enable them to crawl, the 

 Leech belongs. 



It is an aquatic worm, with a flattened body, tapering towards each 

 end, and terminating in circular flattened discs, the hinder one being 

 the larger of the two. It swims with a vertical undulating motion, 

 and moves when out of the water, by means of these discs or suck- 

 ers, fastening itself first by one and then by the other, and alternate- 

 ly stretching out and contracting its body. The mouth is placed in 

 the centre of the anterior disc, and is furnished with three cartila- 

 ginous lens-shaped jaws at the entrance of the alim.entary canal. 

 These jaws are hned at their edges with fine sharp teeth, and meet 

 so as to make a triangular incision in the flesh. The head is fur- 

 nished with small raised points, supposed by some to be eyes. Res- 

 piration is carried on through small apertures ranged along the infe- 

 rior surface. The nervous system consists of a chord extending the 

 whole length, furnished with numerous ganglions. The intestinal 

 canal is straight and terminates in the anus, near the posterior disc. 

 Although hermaphrodite, leeches mutually impregnate each other. 

 They are oviparous, and the eggs, varying from six to fifteen, are 

 contained in a sort of spongy, slimy cocoon, from half an inch to an 

 inch in diameter. These are deposited near the edge of the water, 

 and hatched by the heat of the sun. The leech is torpid during the 

 winter, and casts off, from time to time, a thick slimy coating from 

 its skin. It can live a considerable time in sphagnous moss, or in 

 moistened earth, and is frequently transported, in this manner, to 

 great distances by the dealers. 



Savigny has divided the genus Hirudo of Linnaeus, into several 

 genera. The true leech is the Sanguisuga of this author, and is 

 characterized by its three lenticular jaws, each armed with two rows 

 of teeth, and by having ten ocular points. 



Several species are used for medicinal purposes, of which the 

 most common are the gray and the green leech of Europe, both of 

 which are varieties of the Hirudo medicinalis of Linnaeus, and the 

 Hirudo decora of this country. 



Vol. XXIV.— No. 1. 21 



