88 ENZYMES 



fuuctionating inammary gland is much more active than in the rest- 

 ing ghmd ; and of Schlesinger/- wlio found tliat autolysis was at its 

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

 the fii-st few months of life, and that in conditions associated with 

 emaciation the rate of autolysis varied directly with the degree of 

 enuiciation. Wells ■*^ sought for a possible influence on autolysis by 

 thyroid extract, which increases protein metabolism, but could demon- 

 strate none in vitro; Schryver,*^ however, 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 results of the former 

 observer, but not those of the latter, have l)een confirmed by ^lorse.*^' 



DEFENSE OF THE CELLS AGAINST THEIR AUTOLYTIC ENZYMES 

 The question of wliy the autolytic ferments do not destroy the cells 

 until after death is a revival of the old ]H-oblein of "why the stomach 

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

 protoplasm is essentially different from living protoplasm. ]More ex- 

 act replies are suggested by AViener's studies on the relation of the 

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

 does not begin in an organ until the original alkalinity is neutralized 

 by the acids which are formed in all dead and dying cells.*^ If 

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

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

 the spleen contains an enzyme digesting in alkaline solution, and an- 

 other which acts best in weak acids, the latter appears more promi- 

 nently under ordinary conditions because the spleen and the blood 

 contain antibodies which check the enzyme that acts in alkaline solu- 

 tions, while acids destroy this antibody CHedin).'*^ Organic acids are 

 formed in autolysis of the tissues, aiul the latent period between the 

 time of the removal of an organ from llic body and the appearance of 

 autolysis may be explained partly by the time required for the neu- 

 ti-alization of alkaleseeuce. P)radley " has also ()l)tained evidence that 

 the acid renders the substrate susceptible to digestion by the proteases. 

 The old observation that rigor mortis disappears most rapidly in 

 nuiscles that have been exhausted just before death is also probably 

 exi)lained by the greater amount of acid in such muscles. If we 

 imagine that autolysis is limited to periods when the cells have an acid 

 reaction, however, wo limit tlic i-jiiigc of usefidness in the living cell 



<2 TIofiiK'ifitor'R Bcitr., 1003 (4), !-7 



-•3 Amor. Jour, of Plivsiol., 1004 (11), 351; ooi rolidiatcd Iiv l\<itt maim, Zeit. 

 klin. ^\^Hl., lOin (71), 3(50. 



4<.Toiir. of Plivsiol., mn.T (32), ir>n. 



■••''.Tonr. Biol, riicin., lOl.'i (22), 12r). 



<" Opifi (loc cit.) found, liovvovor, that autolysis of loueocytoa was more rai)id 

 in an alkalino incditun. Docho/, (Proc. Sop. Exp. Biol, and ^I'^d.. 1010 (7). 07) 

 stat-oH that llvfT alno contains an cn/ynip active in an alkaliiii' iiu'diiim. Ii\it which 

 exists as an inactive zyniofrcn until activated by acids. 



••7 Festschrift f. liainniarston, Upsala, 190G. 



