HIRUDO MEDICINALIS. 141 



This small vermiform Amidide has a dark colour and forbidding 

 aspect, and inhabits the stagnant marshes and pools of fresh water 

 throughout Europe. The body is about three inches long, smooth, 

 tapering towards each extremity, composed of numerous rings 

 which are capable of being considerably lengthened or contracted 

 at pleasure. It is of a blackish colour above, with a slight 

 tinge of olive, and is marked by six yellow or buff-coloured 

 longitudinal lines, of which the two exterior ones on each side are 

 interrupted by a chain of longish black spots. The lower surface of 

 the animal is pale olive, variegated with large black or very dark 

 blue irregular spots. Both extremities of the animal are capable 

 of being dilated into a fleshy disc, by means of which it can affix 

 itself firmly to any smooth surface. The mouth is triangular, 

 placed in the centre of a circular or horse-shoe sucker, situated 

 under the head. The mouth is armed with three strong piercers, 

 improperly called teeth, of a rounded form, with sharp cutting edges. 

 They rest on small eminences, and are so placed with regard to 

 each other as to meet in a centre under equal angles. They arc 

 confined in their relative situation by a strong circular ligament 

 which surrounds the oesophagus. The teeth of the Leech are power- 

 ful enough to penetrate not only through the human skin, but 

 also that of horses and cattle. According to Dr. Johnson the eyes 

 of the medicinal leech are two in number, disposed in the form of 

 a crescent on the pointed extremity at the back part of the head.— 

 Fig. A, represents the internal structure of the Leech, slightly mag- 

 nified j a, the three piercers ; b, the abdominal blood-vessel ; c, 

 the lateral vessels \ d, the male organs of generation ; e, the testes ; 

 /, the abdominal vesicles, lying on the surface of the several cells 

 or stomachs ; g, the lateral vesicles secreting the unctuous fluid 

 for lubricating the surface ; B, shews the cocoons of the Leech of 

 their natural size; C, the same cut open ; D, the cocoon contain- 

 ing two young Leeches. 



It was for a long time the received opinion that the Medicinal 

 Leech was viviparous, excluding its young, like the eel, completely 

 formed; and it is but lately that the contrary fact has been 

 ascertained. Mr. Christopher Hebb, an eminent surgeon in 

 Worcester appears to have been the first who notices distinctly 



