82 ENZYMES 



that if he hgated off a portion of the hver and let it remain in situ 

 in the animal the necrotic tissues showed an accumulation of leucine, 

 tyrosine, and other cleavage products of the proteins, 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. The influence of various chemicals 

 upon nitrogen elimination seems to correspond to their effect on auto- 

 lysis (Izar,^^ Laqueur^^). Also, the histologic changes of starvation 

 are similar in many respects to those of autolysis (Casa-Bianchi^^). 

 Among other observations possibly bearing on the same question are 

 those of Hildebrandt,^^ who found that autolysis in the functionating 

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

 of Schlesingeir,^^ who found that autolysis was at its maximum (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^^ sought for a possible influence on autolysis by thyroid extract, 

 which increases protein metabolism, but could demonstrate none 

 in vitro; Schryver,^^ however, reported 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 results of the former observer, but not 

 those of the latter, have been confirmed by Morse. ^^ 



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 ''why the 

 stomach does not digest itself," and the answer that satisfies some is 

 that dead protoplasm is essentially different from living protoplasm. 

 More specific replies are suggested by Wiener's studies on the relation 

 of the reaction of the tissues to their autolysis. He found that auto- 

 lysis does not begin in an organ until the original alkalinity is neutra- 

 lized by the acids which are formed in all dead and djnng cells. ^' If 

 enough alkali is added to the material from time to time to neutralize 

 the acidity as it develops, autolysis docs not take place. Although 



«'Internat. Beitr. Erniihrungstor., 1910 (1), 287. 



" Zeit. physiol. Cheni., 1912 (79), 1 et seq. 



" Frankfurter Zeit. Pathol., 1909 (3), 723. 



"" Hofmeister's Beitrilge, 1904 (5), 463; see also Grinimcr, Hiochcni. Zeit., 1913 

 (53), 429. 



" Hofmeister's Reitr., 1903 (4), 87. 



"* Amer. Jour, of Physiol., 1904 (11), 351; eorrohorated bv Kottiiuinn, Zeit. 

 klin. Med., 1910 (71), '•.m). 



«» Jour, of Physiol., 1905 (32), 159. 



'ojour. Biol. (Jhem., 1915 (22), 125. 



" ()])io (toe cU.) found, liowevcr, llial avitolysis of leucocytes was more rapid 

 in an alkaline inediuiii. Doeliez (.lour. \<]\]). Med., 1910 (,12), tHKi) stnt(>s that liver 

 also contains an enzyme active in an alkaline meiliiun, hut which exists as an 

 inactive zymogen until activated by acids. See also Dernhy." 



