HIRUDO MEDICINALIS 



347 



I. GnathobdellidcB t leeches with jaws. 



These are distinguished by the possession of usually three jaws in the 

 pharynx ; the body consists of twenty-six segments. The posterior sucker 

 is large and flat ; the anterior sucker is smaller. The Hirudinea have 

 five pairs of eyes, the Nephelincs have four pairs. 



Gen. Hirudo, L., 1758. 



The entire body consists of 102 annulations ; five appearing on one 

 segment in the central region of the body. The pharynx has three 

 semi-circular jaws, the arched border of which is beset with numerous 

 teeth (50 100). The male sexual orifice lies between the thirtieth and 

 thirty-first rings, the female orifice between the thirty-fifth and thirty- 

 sixth. There are numerous species, some of which are utilised for medi- 

 cinal purposes. 



i. Hirudo medicinalis, L., 1758. 



It occurs in numerous colour varieties, one of which has been 

 designated Hirudo officinalis, Moq. Tandon. Usually the dorsal surface is 

 greyish-green, and is marked with six rusty- 

 red longitudinal stripes. The ventral surface 

 is olive-green, more or less spotted with black, 

 and marked at the sides with a black longi- 

 tudinal line. The length averages 8 to 12 

 20 cm. This leech lives in swamps, ponds and 

 brooks, overgrown with plants and having a 

 muddy bed. The cocoons are deposited in the 

 soil at the sides. Europe, as well as N. Africa, 

 is its home. At the present day it has been 

 exterminated from most parts of Central Europe, 

 but it is still very common in Hungary. Its 

 use for medicinal purposes is well known. A 

 large leech can suck about 15 grs. of blood 



a I 



FIG. 227. Hirudo medicin- 

 alis. (a) Anterior end,, with 

 open buccal cavity, with the 

 jaws (/.) at the base ; (b) one 



and about the same amount is lost through jaw isolated. (After Claus.) 

 secondary haemorrhage. 



2. Himdo troctina, Johnston, 1816. 

 Syn. : Hirudo inter rupta, Moq. -Tandon, 1826. 



This species measures 8 10 cm. in length. The back is greenish, with 

 six rows of black spots surrounded by red ; the lateral borders are orange- 

 coloured ; the abdomen spotted or unspotted. Its habitat is in N. Africa 

 and Sardinia. It is applied medicinally in England, Spain, France, 

 Algeria, &c. 



