SANGUISUGA. 



The internal digestive apparatus is evidently adapted in the 

 construction of all its parts to form a capacious reservoir for 

 the reception of fluids taken in by suction ; the stomach, in- 

 deed, with the numerous lateral appendages opening from it 

 on each side, would seem to fill the whole body, and, being 

 extremely dilatable, allows the animal to distend itself to a 

 wonderful extent, so that it is not unusual to see a leech when 

 filled with blood expanded to five or six times the dimensions 

 which it presented in an empty state. 



The stomach itself occupies about two thirds of the visceral 

 cavity ; on opening it, it is seen to be divided t>y delicate 

 septa into nine or ten compartments, which communicate 

 freely with each other. In each compartment there are two 

 lateral orifices leading into as many wide membranous pouches, 

 which, although shrunk and flaccid when in an undistended 

 state, are easily filled with fluid introduced into the stomach, 

 and are then swelled out into very capacious bags. Perhaps 

 the simplest way of obtaining a correct idea of the relative 

 sizes and general arrangement of these organs, is to make a 

 cast of their internal cavities when in a state of distention ; 

 this is readily effected by placing a dead leech in warm water 

 until it is slightly heated ; in this state, the pipe of a small 

 injecting syringe can be introduced into the oesophagus so as 

 to fill the stomach and cseca with common wax injection, and 

 if the body be immediately removed into a vessel of diluted 

 muriatic acid, the soft parts will be speedily destroyed, leaving 

 an exact model of the interior. It will then be seen that the 

 lateral caeca increase gradually in size as they approximate 

 the posterior extremity of the body, until the last pair become 

 so large as nearly to fill up the space intervening between the 

 end of the stomach and the anal boundary of the visceral 

 cavity. What is the exact nature of these capacious sacs 

 which thus* open into the stomach of the leech? Are they 

 prolongations of the digestive surface, or are they glandular 

 caeca provided for the secretion of some auxiliary fluids poured 

 into the stomach ? These are questions which admit of con- 

 siderable discussion. On the one hand, there can be little 

 doubt 'that, when the leech is filled with blood, the various 

 caecal pouches become likewise distended, and they are appar- 

 ently as well calculated to effect the digestion of their con- 

 tents as the stomach itself. Those physiologists, however, 

 who embrace a different opinion, support their views by refer- 



5 



