AUTOLYSIS. 17 



having been transformed into the enzyme, and hence are called secre- 

 tion enzymes or extracellular enzymes. 



Besides these extracellular enzymes we also have another group 

 which act within the cells, hence are intracellular and therefore are called 

 intracellular enzymes or endoenzymes. Numerous enzymes besides the 

 yeast zymase belong to this group, and seemingly also oxidases and 

 enzymes having hydrolytic action. The best studied of this group 

 are the proteolytic enzymes, which were first observed by SALKOWSKI 

 and his pupils, and which bring about the self-digestion or autodiges- 

 tion of organs in the absence of micro-organisms. This autodigestion 

 has been the subject of numerous investigations, principally by the HOF- 

 MEISTER school and especially by JACOBY. 1 The latter has given the 

 name autolysis to the process, and he has shown that the enzymes taking 

 part in this action do not come from the digestive tract and are not 

 pepsin or trypsin taken up by the cells. In autolysis we are not only 

 dealing with a proteolysis, but several other processes occur, such as the 

 splitting of fats and carbohydrates, oxidations and reductions, and 

 perhaps also syntheses. 



We therefore generally designate as autolysis all the enzyme actions 

 which take place in removed organs or fluids without the aid of micro- 

 organisms, but it must not be forgotten that autolytic processes may 

 also occur intra vitam under certain conditions. The combined action 

 of various enzymes in autolysis also explains to us why, as especially 

 shown by LEVENE and by JONES, 2 the products obtained by the hydro- 

 lytic cleavage of an organ by means of an acid are somewhat different 

 from those products produced on autolysis. 



It is at present impossible to state what part autolytic processes 

 take in life under physiological conditions, and we can have only con- 

 jectures on this subject. In the autolysis of a removed organ or of one 

 through which the blood is not flowing, the conditions in many ways are 

 quite different from the conditions in life. The products which appear 

 after weeks or months of autolysis, sometimes in very small quantities, 

 do not give any clue to the nature of the processes, and conclusions must 

 be drawn very carefully from these results. 



The post-mortem autolyses, as far as studied, are chiefly proteolyses, 

 but we must not forget that the enzymes taking part are in many cases 

 most active in acid reaction, while they have only a weak action or 



1 A complete summary of the literature of intracellular enzymes and autolysis may 

 be found in Jacoby, Ueber die Bedeutung der intrazellulareri Fermente, etc., Ergeb- 

 nisse der Physiologic, Jahrg. 1, Abt. 1, 1902. See also Preti, Zeitschr. f. physiol. Chem., 

 52; Arinkin, ibid., 53; Hedin, Hammarsten's Festschr., 1906. 



2 Levene, Amer. Journ. of Physiol., 11 and 12, and Zeitschr. f. physiol. Chem., 41; 

 W. Jones, ibid., 42. 



