68 THE ACTION OF THE LIVING CELL 



therefore that any endocellular enzymes found in the 

 medium surrounding cells must have been liberated 

 by necrosis. This concept finds confirmation in the 

 fact that active cytolytic agents or mechanical dis- 

 integration may be employed to achieve that extrac- 

 tion of enzymes from suspensions of cells. 



When, as a result of natural processes or injury, 

 autolysis of cells takes place, the contents of the cell 

 including the endocellular proteases responsible for 

 the autolysis may diffuse out into the surrounding 

 fluids. In the case of higher animals these substances 

 find their vs^ay into the blood and are eventually ex- 

 creted in the urine. This has been proven by Pfeiffer 

 ( 1914) v^ho w^as able to detect the presence of proteo- 

 lytic enzymes in the blood and urine of individuals 

 suffering from extensive burns. Similarly in infec- 

 tuous diseases accompanied by tissue destruction ab- 

 normal quantities of such enzymes have frequently 

 been found in the blood and urine. 



Just as beginning students of physiology frequently 

 ask "Why do not the stomach and intestines digest 

 themselves?" we may ask "Why do not the autolytic 

 enzymes destroy normal cells?" While the first ques- 

 tion has never been satisfactorily answered, it was 

 pointed out at the beginning of this chapter that the 

 hydrogen ion concentration of the normal cell is not 

 sufficiently great to permit activity of the endocellular 

 proteases. 



Prior to the recognition of the importance of the 

 intracellular hydrogen ion concentration in control- 

 ling the activities of the endocellular enzymes, it was 

 believed that autolysis was inhibited solely by the 

 presence of specific antienzymes. Some years ago 



