640 LECTURE XXVII. 



This is a satisfactory explanation as regards the carbohydrates and fats, 

 which, at least with fully developed organisms, can, under certain con- 

 ditions, be regarded solely as combustible materials. The amount of these 

 substances consumed is determined by the amount of energy which is trans- 

 formed in the body. If the supply of carbohydrate or fat is greater than 

 the organism requires at a given time, some of it is laid aside. It is quite 

 different with albumin. The amount at hand regulates the entire metab- 

 olism. The more there is present, the greater the metabolism. Why is 

 so much albumin required? The distinction between circulating albumin, 

 i.e. albumin which is to be used as fuel, and organized albumin, or that 

 which is used for the construction of cell-material, does not help us here. 1 

 As a matter of fact, there is no proof that there is any justification for a 

 sharp distinction between these two kinds of albumin. As we have pre- 

 viously stated, we prefer to consider the total albumin metabolism from a 

 single standpoint and to trace the high requirement of albumin on the part 

 of the animal organism to the fact that in the adaptation of the albumin 

 in the food to the form required by the body there are quite a number of 

 the simpler constituents which are not suitable for synthesizing the new 

 albumin, and these are eliminated. The intestine contains a mixture of 

 different amino acids from which it selects those which suit it and in quite 

 definite porportions. Here again the Law of the Minimum holds. The 

 amount of amino acid which is utilized in the synthesis of new albumin is 

 governed by the amount of that amino acid which is present to the slightest 

 extent relatively. This conception holds only while we have no positive 

 proof that the animal cell is capable of forming one amino acid from another 

 to any considerable extent. For the present our knowledge of the rela- 

 tions concerning the decompositions in the tissues makes any such assump- 

 tion appear improbable. Now the most widely different cell complexes 

 likewise possess their own characteristic albumin. We refer, for example, 

 to the histones, which differ again from the albumin of their nutriment, 

 in this case the serum albumin. Here again the nutriment is broken down, 

 and again the cell chooses those building-stones which it can utilize, and 

 rejects the others. Thus we can imagine that in this reconstruction of the 

 cells, which, although not very extensive of itself, is nevertheless constantly 

 taking place, a considerable supply of albumin is required. When the 

 albumin supply is large, the cell is assured of a sufficient supply of all the 

 most varied building-stones. The unutilized amino acids are at once 

 robbed of their amino group, and perhaps the nitrogen-free chains are 

 further utilized. Even in starvation metabolism the consumption of 

 albumin must be remarkably high, for, in this case also, the albumin trans- 



1 Cf. Emil Abderhalden: Zentr. gesamte Physiol. u. Pathol. des Stoffwechsels, N. F. 

 1 (1906). 



