THE MUTUAL RELATIONS. 319 



of the amino groups and oxidation. We should undoubtedly be making a 

 great mistake if we were to draw the conclusion that all such compounds 

 are decomposed in the same way, merely because in mammals the greater 

 part of the nitrogen from ingested protein, amino acids, and polypeptides 

 appears in the urine. We must not forget that the formation of urea 

 represents only one phase in the disintegration of the amino acids. It 

 certainly does not explain the intermediate albumin metabolism. 



The formation of sugar from amino acids has been regarded as a safe 

 conclusion on account of the fact that these acids are closely related to 

 the fatty acids, and for this reason it may seem superfluous to make such a 

 sharp distinction between the formation of sugar from fats and from albu- 

 min. On the other hand, the objection may be raised that the amino acids 

 which have been studied are derivatives of the lower fatty acids. If we 

 assume that the amino groups are removed from the amino acids while they 

 are in the tissues, thus forming fatty acids, it would be expected that an 

 accumulation of glycogen would result on feeding animals with the fatty 

 acids in question. L. Schwarz * has carried out such experiments, and 

 found that the fatty acids administered did cause an increase in the 

 acetone bodies eliminated, but not in the sugars. 



Embden and Salomon 2 have recently investigated the influence of 

 individual amino acids (alanine, glycocoll) of asparagine and of lactic 

 acid on the elimination of sugar in dogs whose pancreas had been removed. 

 They found that an increase resulted. It is possible that the sugar was 

 formed, in this case, from the above compounds, and that this kind of 

 experiment is more suitable for establishing the formation of sugar than 

 the method of studying the glycogen formation. It is certain that sugar 

 will be formed from albumin or its amino acids only in proportion as sugar 

 is needed by the organism. Further experiments will be necessary to deter- 

 mine whether the administered amino acids have acted in a direct or 

 indirect manner. 



The experiments with the amino acids themselves, therefore, are not 

 as yet such as lead to definite conclusions. We are thus brought back to 

 our former question: Is sugar produced from albumin itself? Claude 

 Bernard made experiments on the formation of glycogen after feeding 

 albumin. He showed that a dog, which had been fed for months only on 

 meat, contained large amounts of glycogen in its liver. He also raised 

 fly-maggots upon boiled egg-albumin or extracted meat, and found large 

 amounts of glycogen. 3 E. Kiilz 4 repeated these last experiments. He 

 divided 72 fresh eggs of Musca vomitoria into two equal groups, and 



1 L. Schwarz: Arch. klin. Med. 76 (1903). 



2 G. Embden and H. Salomon: Hofmeister's Beitr. 6, 63 (1904); ibid. 6, 507 (1904). 



3 C. Bernard: Lecons sur le Diabete, p. 464 (1877). 



4 E. Kiilz: Pfliiger's Arch. 24, 71 (1881). 



