AUTOLYSIS 87 



enzymes have been destroyed by boiling. To determine the 

 rate of autolysis the amount of nitrogen that remains in the 

 form of coagulable compounds, and that which is converted into 

 soluble, non-coagulable compounds (albumoses, peptones, am- 

 monia 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 compounds that remained 

 insoluble or became so after the autolysis was stopped by boil- 

 ing ; 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 condi- 

 tions. In this specimen 90.4 per cent, of the nitrogen was in 

 an insoluble form, and 9.6 per cent, was soluble. Therefore, 

 over half of all the proteid of the liver had been changed into non- 

 coagulable substances in the course of about three weeks (at 37 C.). 

 Since Jacoby's paper appeared, the field has been invaded by 

 many workers, who have examined practically every tissue in 

 the body, and found that all possess the power of self-digestion ; 

 or, in other words, proteases are present in every cell in the body. 

 The rate of digestion is very different in different organs, how- 

 ever, liver digesting rapidly while brain and muscle tissue digest 

 much more slowly. These intracellular proteases are not alto- 

 gether like either pepsin or trypsiu, for they split proteids to 

 its simplest elements, whereas pepsin carries the digestion only 

 to the peptone stage (under ordinary conditions) and unlike 

 trypsin their action is most marked in a faintly acid medium, 

 and is entirely checked by alkalies no stronger than 0.4 per cent. 

 NaOH, according to Wiener. 1 Furthermore, the cleavage prod- 

 ucts seem to contain a much larger proportion of the nitrogen 

 in the form of ammonia and its compounds than is the case with 

 tryptic digestion. It is quite probable that in autolysis several 

 intracellular enzymes are in action, some of which may not be 

 present in pancreatic or gastric juice. On the whole, however, 

 the products are quite similar to those obtained by tryptic diges- 

 tion. To give a concrete example, Dakin 2 detected in the prod- 

 ucts of autolysis by the kidney in acid solution, the following 

 substances : Ammonia, alanin, a-aminovalerianic acid, leucin, 

 a-pyrollidin carboxylic acid, phenylalanin, tyrosin, lysin, histidin, 

 cystin, hypoxanthin, and indol derivatives, including probably 

 tryptophan. 



1 Centr. f. PhysioL, 1905 (19), 349. 



2 Jour, of Physiology, 903 (30), 84. 



