THE MUTUAL RELATIONS. 305 



of food is of little consequence, or at least all of our present knowledge 

 of albumin metabolism speaks against it. We need only think of the 

 possibility of fats and carbohydrates being produced from albumin. Now 

 we have already seen that a large part of the elementary components of 

 the proteins are very closely related to the lower members of the normal 

 fatty acid series. We know further, that only a part of the carbon leaves 

 the organism in combination with the nitrogen of the individual amino 

 acids. A portion of the carbon chain must remain behind. What becomes 

 of this is not yet apparent. Right here the investigation must start con- 

 cerning the transformations of the albumins into fats and carbohydrates, 

 for all such changes must result from these carbon chains. We have, to 

 be sure, no positive proof that such transformations do take place. 



Perhaps the intermediate product, glucosamine, may throw some light 

 upon the formation of albumin from carbohydrates in plants, and, con- 

 versely, the production of carbohydrates from albumins in the animal 

 organism. It is a derivative of glucose (or of mannose), and is closely 

 related on the one hand to the sugars, and on the other, to the oxyamino 

 acids. It is certainly not without significance, that nature has provided 

 such connecting links. We recall the following formulae: 



CH . (OH) CH . (NH 2 ) CH . (NH 2 ) CH . (NH 2 ) 



CH : O CH : O COOH COOH 



d-Glucose Glucosamine Lysine Leucine 



The carbohydrates, as we have already seen, are related to the poly- 

 hydric alcohols on the one hand, and to various acids of different char- 

 acter on the other. We can thus, either directly or indirectly, connect 

 large groups of different compounds with the sugars. We are still entirely 

 in the dark regarding the method of formation of innumerable tannins, 

 ethereal oils, alkaloids, etc., which occur in the plant organisms. All 

 of these must ultimately be referred to the carbon dioxide of the air. 

 What relations they possess to the carbohydrates is still entirely beyond 

 our knowledge; in fact, owing to their great complexity, we are almost 

 forced to the conclusion that they are not at all related. C. Harries 1 has 



1 C. Harries: Ber. 38, 1195 (1905). 



