308 EETROGEESSIVE CHANGES 



that not all parts of a cell die at the same time ; i. e., the causes 

 of different chemical processes of the cell reside in its different 

 intracellular enzymes, and these are not necessarily destroyed 

 alike by the same agents. 



We recognize that after an animal is dead as a whole the 

 various cells of its body do not die for some time, as shown by 

 the following examples : (1) We can cause the heart to beat 

 for a considerable period after its removal from the body ; (2) 

 if we perfuse a mixture of glycocoll and benzoic acid through 

 the kidney of a recently killed animal, synthesis of these sub- 

 stances into hippuric acid will occur ; and (3) the epithelium of 

 the skin can be removed from the body of an animal long after 

 death and transplanted successfully on another animal. So, too, 

 in ordinary cell death (necrobiosis) not all the enzymes are 

 destroyed together. When all are destroyed at once, as by 

 strong chemicals or by heat, the customary disintegrative changes 

 do not take place. If, however, not all the enzymes are thrown 

 out of function, then the others may be able to act, producing 

 the disintegrative changes by which histologists ordinarily 

 recognize cell death. These disintegrative changes are, for the 

 most part, apparently brought about by the intracellular pro- 

 teases, that is, through autolysis. This may be shown as 

 follows : l If we take two pieces of fresh normal tissue from an 

 animal, and in one kill the enzymes by heating to 100 C., 

 then implant both aseptically into the abdominal cavity of an 

 animal of the same species, it will be found that the changes 

 that follow in the two will be very unlike. In the unheated 

 tissue nuclear changes soon occur, so that they lose their capac- 

 ity for taking up basic stains, the cytoplasm becomes granular 

 and fragmented, the tissue becomes friable so that it is difficult 

 to secure good sections, and the changes are in general similar 

 to those seen in areas of necrosis. The boiled tissue, on the 

 other hand, retains its capacity for nuclear staining for months, 

 except at the periphery, where it is slowly attacked by leucocytes 

 and the enzymes of the blood plasma. Therefore it would seem 

 that the characteristic changes of necrosis depend chiefly upon 

 the intracellular enzymes, rather than upon the infiltrating 

 plasma as Weigert 2 and other early writers imagined. In 

 areas of anemic necrosis (see " Infarcts " ) we have another case, 

 in which the oxidizing enzymes are thrown out of function 

 through lack of oxygen, while the other enzymes are, presum- 

 ably, at first unaffected. From studies of infarcts it would seem 



1 Wells, Jour. Med. Kesearch, 1906 (15), 149. 



2 Cent. f. Path., 1891 (2), 785. 



