PROBLEMS OF PHYSIOLOGICAL CHEMISTRY. 155 



investigator also claims the presence in the spleen of a related enzyme, 

 called adenase, which transforms adenin into hypoxanthin. The infer- 

 ence is that in many glands and tissues there are specific enzymes, as 

 yet undiscovered, which may be responsible for at least some of the 

 transformations known to occur there. 



That autolysis may be a possible explanation of the process of ani- 

 mal metabolism has been suggested by Levene * and also by Wells, f It 

 has been clearly indicated by such able workers as Salkowski, Jacoby 

 and others, that practically all animal cells contain within themselves 

 ferments or enzymes that are capable, under suitable conditions, of 

 digesting or breaking down the cell contents by a process similar to 

 ordinary proteolysis, and it may perhaps be assumed that all active 

 cells carry forward their ordinary metabolic processes by the agency 

 of these intra-cellular ferments. Moreover, it is not inconceivable 

 that ferments or enzymes of several kinds may exist side by side in a 

 given group of cells, just as they are known to exist in the pancreas, by 

 which we might infer the possibility of a series of transformations 

 taking place at essentially the same time, through the harmonious action 

 of a row of enzymes physiologically quite distinct. 



Further, the recently discovered reversible action of enzymes, on 

 which we have at command so much valuable work, suggests the pos- 

 sibility of a maintenance of cell equilibrium through this peculiarity 

 of action, thus affording a tangible explanation of the means by which 

 intra-cellular nitrogenous or proteid equilibrium is maintained, the 

 various cells of the body building up or breaking down the proteid 

 matter of their own tissues as circumstances require. If these ideas 

 are true, then our conception of ferment action must be considerably 

 broadened, and we have before us the possibility of explaining many 

 of the phenomena of tissue metabolism by the action and interaction 

 of intra-cellular enzymes. This is a problem well worthy of broader 

 study, with a view to the elucidation of the general laws that govern 

 tissue changes in general. In this connection we also have suggested 

 the possibility of interaction of another kind, viz., that interdependence 

 of one tissue or gland upon another for the full development of its 

 functional activity, as illustrated by the part played by the enterokinase 

 of the intestinal glands in the development of an active trypsin from 

 the zymogen of the pancreatic cells, and by the action of the internal 

 secretion of the pancreas upon the inert constituents of the muscle to 

 develop in the latter an active glycolytic enzyme. How far this gen- 

 eral principle extends in the metabolic phenomena of the body is en- 

 tirely problematical, but merits careful study. Here, then, we have an 



* 'Die Endprodukte der Selbstverdauung tierischer Organe,' Zeitschrift fur 

 physiologische Chemie, Band 41, p. 393. 



t ' On the Relation of Autolysis to Proteid Metabolism,' Amer. Journal of 

 Physiology, Vol. 11, p. 351. 



