PRESENT PROBLEMS 339 



nel because of the peculiar chemical nature of the cell protoplasm. 

 Once started, the process of katabolism takes a definite course, with 

 formation invariably of the same products, because that particular 

 cell protoplasm, owing to its peculiar make-up, tends to break down 

 along certain definite lines of cleavage, as it were, and so the products 

 split off are always the same. 



We already have considerable knowledge which tends to indicate 

 that the cells of individual organs and tissues have a certain individ- 

 uality as regards their primary components, notably in the nucleo- 

 proteids present, but our knowledge is by no means complete enough 

 to permit of broad generalization. The problem is an interesting one, 

 and permits of a definite answer by the application of thorough and 

 persistent investigation. 



As an allied question, more or less in harmony with what has just 

 been said, reference may be made to the part which ferments and 

 enzymes possibly play in initiating and carrying forward tissue 

 changes, as well as the metabolic changes that occur in glandular 

 organs. Ferments have come into such prominence of late years as 

 responsible agents for so many transformations that we may well 

 query whether their influence does not extend far beyond the limits 

 originally assigned to their field of activity. The discovery of oxidases 

 and the part which these agents may play in tissue changes, the un- 

 doubted existence of ferments in such glands as the thymus, supra- 

 renal, spleen, etc., by which the recently studied autolytic changes in 

 these glands are produced, raise the question whether ferments or 

 enzymes are not far more largely responsible for the many trans- 

 formations that take place in active tissues than has been hitherto 

 supposed. Consider for a moment the peculiar products which result 

 from the self-digestion (autolysis) of many of the glands so far 

 studied. Note how the nucleo-proteid of the thymus, for example, 

 breaks down, yielding xanthin and a little hypoxanthin, together with 

 uracil, but no guanin, adenin, or thymin. 1 How the adrenal nucleo- 

 proteid likewise yields by autolysis considerable xanthin, but only 

 traces at the most of the other alloxuric bases (Jones). By the self- 

 digestion of the spleen, guanin as well as hypoxanthin is conspicuous, 

 but it is a noticeable fact that in the autolysis of the thymus, for ex- 

 ample, there is no appreciable amount of leucin to be detected, thus 

 indicating that the above autolytic changes are not due to any or- 

 dinary proteolytic enzyme, but to some peculiar enzyme which acts 

 directly and solely upon the nucleo-proteids, splitting off certain of the 

 contained alloxuric groups. In harmony with this view, Jones has just 

 announced the presence in the pancreas, thymus, and adrenals, of an 

 enzyme to which he gives the name of guanase, which has the power of 



1 Jones, Ueber die Selbstverdanung von Nucleoproteiden, Zeitschrifl fur physiolo- 

 gische Chemie, Band 42, p. 35. 



