i54 POPULAR SCIENCE MONTHLY. 



travels along a certain definite channel 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 

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

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

 teids 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. Fer- 

 ments 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 undoubted existence of 

 ferments in such glands as the thymus, suprarenal, spleen, etc., by 

 which the recently studied autolytic changes in these glands are pro- 

 duced, raise the question whether ferments or enzymes are not far more 

 largely responsible for the many transformations 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 nucleoproteid of 

 the thymus, for example, breaks down, yielding xanthin and a little 

 hypoxanthin, together with uracil, but no guanin, adenin or thymin.* 

 How the adrenal nucleoproteid 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 hypox- 

 anthin is conspicuous, but it is a noticeable fact that in the autolysis 

 of the thymus, for example, there is no appreciable amount of leucin to 

 be detected, thus indicating that the above autolytic changes are not 

 due to any ordinary proteolytic enzyme, but to some peculiar enzyme 

 which acts directly and solely upon the nucleoproteids, 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 transforming guanin into xanthin. The same 



* Jones, ' Ueber die Selbstverdauung von Nucleoproteiden,' Zeitschrift fur 

 physiologische Chemie, Band 42, p. 35. 



