Leeches. 47 1 



head than the tail, composed of 95 to 100 transverse rings, flat- 

 tened on the ventral aspect and somewhat less so on the dorsal, 

 and furnished with two suckers a caudal and a cephalic, the last 

 having the oral opening. The oral sucker has three rings within 

 each other and an orifice in three slits arranged one forward and 

 two lateral so as to have a triradiate appearance. Each slit cor- 

 responds to a denticulated crest or jaw and the three perforate the 

 skin so as to form a triangular wound. The leech bite can 

 always be recognized by this triangular outline. Leeches are 

 hermaphrodite vet the congress of two individuals is necessary to 

 reproduction. 



The different kinds of leeches that interest veterinarians are 

 mainly the following : — 



The Medicinal Leech (Hirudo Medicinalis) is dull olive or 

 olive brown on the back, with six yellowish spots and lateral 

 yellowish stripes, while the belly is grayish with black spots. 

 The body is composed of 95 to 100 rings and the mouth is sur- 

 rounded by four incomplete rings. These are found naturally in 

 ditches and ponds, with pure running water, weeds for shelter 

 and muddy bottom and banks. They bite man or beast that 

 may wade in the water. They are more or less common in Europe, 

 Western Asia and Africa. A number of varieties have been de- 

 scribed, one of the most common of which is the Green Leech 

 (H. Officinalis) distinguished by its greenish shade and the 

 absence of spots on its venter. 



The Trout Leech (H. Troctina, Interrupta) about the same 

 size as the medicinal leech (80 to 100 mm. when extended) has a 

 generally greenish back, with bright round spots, and orange or 

 reddish borders. This is an inhabitant of the fresh running 

 waters of Algiers and Northern Africa generally, and has been 

 used in medicine as a substitute for the medicinal leech. 



The Hirudo Decora, the common leech of N. America is 

 bluish in color, with about twenty-two reddish points on the 

 dorsum, and a series of lateral black spots. Found in the run- 

 ning fresh waters this is smaller than the medicinal leech drawing 

 about a drachm of blood instead of i^ drachm. It fastens on 

 animals and men that wade the streams. 



The Horse Leech, Haemopis Sanguisuga or Vorax, of nearly 

 the same size as the medicinal leech is soft, greenish brown on 



