CHAP, i.] TISSUES AND MECHANISMS OF DIGESTION. 353 



frequently found partially digested, viz. in cases when death has 

 taken place suddenly on a full stomach. In an ordinary death, 

 the membrane ceases to secrete before the circulation is at an end. 

 That there is no special virtue in living things which prevents 

 their being digested is shewn by the fact, that the leg of a living 

 frog or the ear of a living rabbit introduced into the stomach of a 

 dog through a gastric fistula is readily digested. It has been 

 suggested that the blood-current keeps up an alkalinity sufficient 

 to neutralize the acidity of the juice in the region of the glands 

 themselves , but this will not explain why the pancreatic juice, 

 which is active in an alkaline medium, does not digest the 

 proteids of the pancreas itself, or why the digestive cells of the 

 bloodless actinozoon or hydrozoon do not digest themselves. We 

 might add, it does not explain why the amoeba, while dissolving 

 the protoplasm of the swallowed diatom, does not dissolve its 

 own protoplasm. We cannot answer this question at all at 

 present, any more than the similar one, why the delicate proto- 

 plasm of the amoeba resists during life the entrance into itself 

 by osmosis of more water than it requires to carry on its work, 

 while a few moments after it is dead water enters freely by 

 osmosis, and the effects of that entrance become abundantly 

 evident by the formation of bullse and the breaking up of the 

 protoplasm. 



