RELATION OF AUTOLYSIS TO METABOLISM 89 



and other splitting products of the proteids, which suggested 

 that these same bodies are being formed in the liver constantly, 

 but that they are as constantly removed from the normal organs 

 by the circulating blood, or are undergoing further alterations 

 which cease when the circulation is checked. Among other 

 observations possibly bearing on the same question are those of 

 Hildebrandt, 1 who found that autolysis in the functionating 

 mammary gland is much more active than in the resting gland ; 

 and of Schlesinger, 2 who found that autolysis was at its max- 

 imum (in rabbits) in new-born animals, decreasing rapidly in 

 the first few months of life, and that in conditions associated 

 with emaciation the rate of autolysis varied directly with the 

 degree of emaciation. Wells 3 sought for a possible influence 

 on autolysis by thyroid extract, which increases proteid metab- 

 olism, but could demonstrate none in vitro. Schryver, 4 how- 

 ever, found that autolysis was more rapid in the liver of dogs 

 fed thyroid extract for some days before death than it was in 

 control animals. 



The possibility of synthesis of proteids by the autolytic en- 

 zymes seems not to have been investigated. Proteid synthesis 

 seems to be accomplished on a large scale in the wall of the 

 intestine, and the enzyme most prominent in this tissue is the 

 erepsin of Cohnheim. In this connection the statement of 

 Vernon 5 that erepsiu or a similar enzyme is present in all the 

 tissues of the body may be of some significance. Erepsin is 

 very similar to the autolytic enzymes, except that it does not 

 attack proteids until they have been already split as far as 

 proteoses, and the products of its action are not quite the same 

 (Cohnheim). As yet the exact relation of erepsin to synthesis 

 is quite unknown. The chief positive evidence yet obtained 

 concerning proteid synthesis by proteases is the " plastein reac- 

 tion/ 7 i. e., the formation of an insoluble plastein when pro- 

 teases are added to proteose solution ; this occurs not only with 

 trypsin and pepsin, but also with extracts of organs containing 

 autolytic proteases. 6 



DEFENSE OF THE CELLS AGAINST THEIR AUTOLYTIC ENZYMES 



The question of why the autolytic ferments do not destroy 

 the cells until after death is a revival of the old problem of 



1 Hofmeister's Beitriige, 1904 (5), 463. 



2 Ibid,, 1903 (4), 87. 



3 Araer. Jour, of Physiol., 1904 (11), 351. 

 * Jour, of Physiol., 1905 (32), 159. 

 5 Jour, of Physiol., 1904 (32), 33. 

 6 Niirnberg, Hofmeister's Beitr., 1903 (4), 543. 



