76 ENZYMES 



dead tissues within the body which occurred without putrefaction, 

 and, as he noted, resembled the effects of the digestive ferments. It 

 was nearly twenty years later that Salkowski^ showed definitely that 

 this softening of dead tissues was really brought about through a true 

 digestion by intracellular enzymes, which produced the same splitting 

 products that were at that time considered characteristic for tryptic 

 digestion (leucine and tyrosine). The process he named "autodiges- 

 tion." This important observation remained almost unnoticed for 

 ten years more, when Jacoby,^ in 1900, took up the investigation of 

 this matter of cellular self-digestion, and after this the importance of 

 the principles involved became for the first time generally appreciated. 

 Jacoby rechristened the process "autolysis," by which name it is now 

 commonly known. 



AUTOLYSIS^ 



Autolysis is generally studied by the method used bj' Salkowski, 

 which depends upon the difference in the susceptibility of bacteria 

 and of enzymes to antiseptics. The organs are ground to a pulp, 

 placed in flasks with or without the addition of water or dilute acids, 

 and bacterial action is prevented by the addition of antiseptics that 

 are not poisonous to enzymes — 'toluene and chloroform are most com- 

 monly used. It is possible also to secure organs in an aseptic con- 

 dition and to permit them to undergo autolysis without the use of 

 antiseptics, but the practical difficulties are such that this method 

 is seldom used — it is sometimes designated as "aseptic autolysis, in 

 contradistinction to antiseptic autolysis by the Salkowski method. In 

 a short time it can be seen that digestive changes have taken place, 

 particularly if comparisons are made with control flasks in which 

 the enzymes have been destroyed by boiling. To determine the rate 

 of autolysis the amount of nitrogen that remains in the form of coagu- 

 lable compounds, and that which is converted into soluble, non- 

 coagulable compounds (albumoses, peptones, ammonia compounds, 

 amino-acids, etc.), is compared. The method may be illustrated by a 

 concrete example: A given specimen of emulsionized liver tissue was 

 permitted to digest itself for twenty-two days. At the end of that 

 time 39.4 per cent, of the nitrogen was still contained in the com- 

 pounds that remained insoluble or became so after the autolysis was 

 stopped by boihng; while 60.6 per cent, of the nitrogen was in a 

 soluble form. A control specimen from the same liver was boiled 

 while fresh to kill the enzymes, and then let stand under the same 



3 Zeit. f. klin. Med., 1890, supplement to Bd. 17, p. 77. 



•" Zeit. f. physiol. Cheni., 1900 (30), 149. 



5 Resviiiu'; of literature l)v Salkow.ski, Deut.schc Klinik, 1903 (11), 147; also see 

 Schlesinger, HofnieistxT's lieitriiKe, 1903 (4), 87; Oswald. Biochem. Centr., 1905 

 (3), 365; Levene, Jour. Ainer. Med. Assoc., 1906 (46). 77t); Nicolle, Ann. Inst. 

 Pasteur. 1913 (27), 97; von Fiirth, " Chemistry of Metal)olisiii," Ainer. Transl., 

 1916. 



