ALBUMINS OR PROTEINS. 223 



from its tissues may possibly throw some light on the fact that the animal 

 cell is continuously using up proteins in its economy. Every individual 

 body-cell is capable of forming new cells, either in renewing its own 

 structure, or in giving off cells. It obtains the other necessary elementary 

 constituents from the storehouses of the tissues. Fats and carbohy- 

 drates are held in reserve. The animal organism has no storeroom for 

 its albumin. It is only capable of accumulating albumin under very 

 specific conditions. Even these stores are removed when the nutrition 

 returns to its normal state. Every cell is evidently restricted to a definite 

 amount of albumin, to which it closely adheres. If the animal organism 

 possesses more fat or carbohydrate than it requires, it will store them up. 

 There is no increase in the metabolism. If, on the other hand, the amount 

 of albumin administered be increased, then the metabolic changes are 

 increased. The albumin governs the whole animal organism. We will 

 add, that from the chemical point of view it is perfectly possible for the 

 cell, under certain conditions, to produce all its other organic requirements 

 from albumin. It is possible that it may produce fats and carbohydrates 

 from albumin. Albumin, from this point of view alone, is therefore a 

 valuable food-material. Whether such changes actually occur under 

 normal feeding, that is, with a sufficiency of fats and carbohydrates, is 

 very problematical, in fact hardly to be assumed. 



We will furthermore add that the albumin in the nourishment, which 

 certainly serves for manifold purposes, may not all participate in the 

 true cell metabolism. We arrive at this conclusion, from the fact that 

 the animal organism evidently produces its body albumin from such 

 differently constituted proteins in our foods. Waste products may very 

 easily arise. Let us recall the experiment of feeding a horse with gliadine, 

 which is so rich in glutamic acid. As this animal was only capable of 

 utilizing one-fifth of this amino acid for the synthesis of serum-albumins, 

 the remainder must have been consumed in some other manner. It is 

 possible that the animal cells possess the ability of producing other amino 

 acids from a specific one, but we can also imagine that when the nutrient 

 albumin is transformed into body albumin, many of the elementary com- 

 ponents are cast aside and directly consumed. We must not forget that 

 we are now entering into a realm which has so far been but little investi- 

 gated. We might expect from this assumption that the animal organism 

 would be satisfied with the smallest amounts of those albuminous sub- 

 stances whose compositions were closely related to its own proteins. In 

 this case most of the elementary components would be available. At any 

 rate, we are not justified in drawing the conclusion that the proteins 

 in the food take part in the metabolism of the cells from the fact that 

 the nitrogen in the case of mammals reappears in a short time as 

 urea. We find that amino acids and polypeptides are eventually broken 



