288 LECTURE XIII. 



causes of the well-known metabolic derangement, gout, which is un- 

 doubtedly closely related to a disturbance of the purine assimilation. 

 Our uncertainty begins when we proceed to follow the behavior of the 

 nucleic acids in the alimentary tract, although we are a little better informed 

 regarding the decomposition of the nucleoproteids themselves. The latter 

 are, at the start, vigorously attacked by pepsin and hydrochloric acid 

 in the stomach. The loosely-linked albuminous component is split off 

 and converted into peptones. Nuclein then separates in an insoluble 

 form, but later on is partially dissolved. Trypsin likewise separates 

 the albuminous component from the nucleoproteids. The nucleic acids, 

 however, seem to remain entirely unaltered. They must, therefore, 

 occupy a class by themselves among the food materials, because all the 

 others so far discussed are largely disintegrated in the intestine in order 

 to supply the tissue cells, and partly those of the intestine itself, with 

 the necessary material for their individual needs. We would expect, 

 a priori, that the nucleic acids would also have to be disintegrated to 

 make them available. Up to the present time but one ferment has been 

 isolated from the tissues capable of separating nucleic acids into their 

 components. This is the so-called nuclease. 1 Trypsin destroys this 

 ferment. Nuclease has been found in the pancreas of the dog and the 

 thymus gland of the calf. Undoubtedly, such ferments must be widely 

 distributed in the tissues. They account for the first stages of the cleavage 

 and degradation of the nucleic acids. Recent investigations 2 have shown 

 that neither the active nor the inactive pancreatic juice is able to decom- 

 pose the nucleic acids into their components; both, however, are capable 

 of so altering them that their entire characteristics are changed, thus 

 making them more easily dialyzable. Even the cell walls of the intestine 

 possess ferments which are capable of completely decomposing the altered 

 nucleic acids. The animal organism evidently treats this valuable material 

 in a very economical manner. The nucleic acid cleavage-products are 

 difficultly soluble in water, and not easily absorbed, as feeding experi- 

 ments with purine bases have proved. These experiments indicate that 

 the complete disintegration of these compounds takes place only in the 

 walls of the intestine. Material, foreign to the organism, is there pre- 

 pared for its requirements. We are unacquainted with the exact manner 

 in which the pancreatic juice changes the nucleic acids. It may possibly 

 be that it acts as the beginning of a hydrolytic decomposition. The 

 disintegration proceeds in stages, and we must expect to meet complexes 

 analogous to the peptones, and dextrins. We have not the least doubt 

 but that the nucleic acids very closely resemble the albumins in their 

 entire construction and the way they are broken down. 



1 F. Sachs: Z. physiol. Chem. 46, 337 (1905). 



3 E. Abderhalden and A. Schittenhelm: ibid. 47 (1906). 



