PRINCIPLES OF AUTOLYSIS 77 



conditions. In this specimen 90.4 per cent, of tlie nitrogen was in 

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

 half of all the protein of the liver had been changed into non- 

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

 Complete disintegration of the proteins with liberation of all the 

 amino-acid complexes is probably never reached. Of 45.8 grams of 

 amino-acids present in 100 grams of liver, in ten days' autolysis there 

 had been set free but 1.85 gm., after 30 daj^s 10.1 gm., and after 50 

 days but 29.1 gm. (Abderhaldcn and Prym.'') Bj' determining the 

 freezing point and conductivitj'' of autolyzing mixtures, valuable 

 evidence can be obtained as to the rate of change, which, in some cases, 

 is much more significant than the usual estimation of soluble and in- 

 soluble nitrogen (Benson and Wells^). Titration of the free amino- 

 acids b}' the formaldehyde method, together with the estimation of 

 proteose and peptone nitrogen, also furnish valuable information, 

 while the Van Slyke method of determining free amino-acids is 

 especially useful for this purpose. 



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

 workers, who have examined practically everj^ 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 hodij} The rate of digestion 

 is very different in different organs, however, liver digesting rapidly 

 while brain and muscle tissue digest much more slowly, aud the auto- 

 lytic activity varies under different conditions;^ thus, fever causes a 

 great increase in the proteolytic activity of the muscles.^*' The char- 

 acter of the antiseptic used modifies greatly the rate, salicylic and ben- 

 zoic acids giving the most rapid autolysis, while of non-acid antiseptics 

 toluene is perhaps the least inhibitory. One of the most important 

 factors in modifying the rate of autolysis is the H-ion cencen- 

 tration developing in the tissues. ^^ Acidity acts, partly, at least, by 

 so modifying the substrate that the enzj^mes can attack it, and a very 

 small excess of acid will destroy the enzymes; Bradley^'- estimates this 

 destructive acidity at about that concentration of H-ions which is 

 indicated by methyl orange and Congo red, the maximum" autolysis 

 being obtained with an acidity at about pH = 6.00. A reaction 

 approximating that of blood (pH = 7.4 — 7.8) reduces autolysis to a 

 minimum. A latent period has been observed before autolysis in 



«Zeit. physiol. Chem., 1907 (53), 320. 



^ Jour. Biol. Chem., 1910 (8), 61. 



^ Except, perhaps, the red corpuscles (Pincussohn and Roques, Biochem. Zeit., 

 1914 (64), 1). 



* Concerning autolysis of skin, see Sexsmith and Petersen, Jour. Exp. Med. 

 1917 (27), 273. 



'" Aronsohn and Blumenthal, Zeit. klin. Med., 1908 (65), 1. Striated muscle 

 autolyzes much less rapidly than cardiac and unstriated. (Bradley, Proc. Am. 

 Soc. Biol. Chem., 1918 (33), xi). 



" See Morse, Jour. Biol. Chem., 1916 (24), 163. 



'Uour. Biol. Chem., 1915 (22), 113; 1916 (25), 261. 



