226 LECTURE XI. 



a small, or even no, increase in the amount of urea in the urine, for the 

 reason that other nitrogenous decomposition products are also formed, 

 which, in' part, are direct indications of incomplete combustion of the 

 albumin. We observe an increased albumin disintegration during many 

 pathological processes, such as fevers, phosphorus, arsenic and antimony 

 poisoning, and also with an insufficient supply of oxygen. We shall see 

 later that an increased elimination of nitrogen follows the administration 

 of the thyroid gland, and of the hypophysis, or of extracts obtained from 

 these organs. In Morbus Basedowii we shall become acquainted with a 

 disease, which is evidently related to the changes in metabolism of the 

 thyroid gland, and is characterized by an increased disintegration of 

 albumin. 



We are here chiefly interested in this question: How is urea produced 

 from albumin? We cannot give a direct answer. We may in fact add 

 that the formation of urea from albumin has never been satisfactorily 

 explained. We are accustomed to assume that a hydrolytic cleavage pre- 

 cedes the oxidation of the absorbed and assimilated nourishment. The 

 cell evidently does not consume glycogen, but d-glucose, and perhaps not 

 even this directly, but only after the cell has altered it in a manner as yet 

 undetermined so that oxygen can attack it. We assume likewise that the 

 fats are decomposed into their components and are then completely oxi- 

 dized. Many observations indicate that the proteins in the cell-metabo- 

 lism are first hydrolyzed and then the cleavage-products are consumed. 



An observation by Drechsel * seemed to place the proteins in an excep- 

 tional position. Drechsel obtained urea from albumin simply by hy- 

 drolysis, although the yield was very small. We know to-day that the 

 amount of urea thus formed is dependent on the quantity of arginine 

 present in the protein. 



A. Kossel and H. D. Dakin 2 have also recently shown that urea may be 

 obtained from arginine in the tissues. They permitted erepsin to act on 

 clupein sulphate, and found that this protamine was attacked by the 

 ferment. After a time all of the arginine present in the molecule was 

 found in the digesting fluid. A repetition of the experiment, using another 

 erepsin preparation, failed to remove the biuret reaction, even when the 

 process was allowed to continue through a long period of time. Higher 

 complexes remained unattacked. 



On analyzing the digesting mixture Kossel and Dakin found the follow- 

 ing products: (1) protone, the peptone of the protamine; (2) arginine; (3) 

 ornithine; (4) urea; and (5) amino- valeric acid. This discovery indi- 

 cates that the erepsin further hydrolyzes a portion of the arginine into 



1 Ber. 23, 3096 (1890). 



1 Z. physiol. Chem. 41, 321 (1904) ; 42, 181 (1904). Miinchener med. Wochenschrift 

 No. 13, 1904. 



