INTERNAL ANATOMY 



Digestive Tract. 



The digestiv tract is a more or less highly differentiated tube 

 extending from one end of the body to the other. In most of the 

 Minnesota leeches several distinct regions can be easily recognizd 

 in it. But there is no uniformity in the differentiation nor in the 

 names applied to the several regions by the various writers. 



The Mouth 



is on the ventral surface at the anterior end in the center of a more 

 or less well developt sucker. In one group of leeches, cald the 

 Gnathobdellidae, it is provided with three "jaws" that radiate from 

 a common point with an angle of about thirty degrees between the 

 middle jaw and each of the outer of the trio. The free edge of each 

 jaw is curvd and coverd with a horny (chitinous) band that is 

 notcht like a saw. When these jaws are workt back and forth on 

 the skin of the host by the special muscles attacht to them they cut 

 a ragged wound in the skin, which bleeds much more freely than 

 would a single clean cut. The mouth opens into a short portion 

 cald the 



Farynx or Esofagus. 



This is a muscular region which by the action of its muscles 

 can create a strong suction thru the mouth. In one group of leeches, 

 cald the Rhyncobdellidae , it can be protruded and is often spoken of 

 as the proboscis. In the true bloodsuckers this region has opening 

 into it a large number of unicellular glands cald salivary glands. 

 They are located mainly in the two or three somites immediately 

 in front of the anterior reproductiv opening. Hemingway has also 

 describd a multicellular gland he calls the esofageal gland that 

 opens into this region thru a cellular duct. For the full account 

 see page 49. These glands produce a secretion which prevents the 

 coagulation of the blood suckt from the host. The esofagus opens 

 into the largest portion of the digestiv tract, cald 



