STARVATION , 607 



he had to take the following amounts : 30 gm. meat protein, 31 gm. milk 

 protein, 34 gm. rice protein, 38 gm. potato protein, 54 gm. bean protein, 

 76 gm. bread protein, and 102 gm. Indian-corn protein. The organism 

 is evidently able to satisfy its protein demands much more readily with 

 meat than with vegetable proteins. 



This variability in the food value of different proteins depends on their 

 ultimate structure that is, on the proportion and manner of linkage 

 of the various amino acids that go to build up the molecule. In no two 

 proteins are these building stones, as they are called, present in exactly 

 the same proportions, some proteins having a preponderance of one or 

 more and an absence of others, just as in a row of houses there may be 

 no two that are exactly alike, although for all of them the same build- 

 ing materials were available. Albumin and globulin are the most im- 

 portant proteins of blood and tissues, so that the food must contain the 

 necessary units for their construction. If it fails in this regard, even to 

 the extent of lacking only one of the units, the organism will either be 

 unable to construct that protein, and will therefore suffer from partial 

 starvation, or it will have to construct for itself this missing unit. It 

 is therefore apparent that the most valuable proteins will be those that 

 contain an array of units that can be reunited to form all the varieties 

 of protein entering into the structure of the body proteins. Naturally, 

 the protein which most nearly meets the requirements is meat protein, 

 so that we are not surprised to find that less of this than of any other 

 protein has to be taken to gain nitrogenous equilibrium. 



The most exact information regarding the "food value " of different 

 proteins has been secured by observations on the rate of growth of young 

 animals. This method yields more reliable information than can be 

 secured by studies on the nitrogenous balance, because it is not usually 

 possible to keep up the latter observations for a sufficient period of 

 time, or to secure an adequate number of data. During growth the 

 building-up processes are in excess of the breaking-down, so that the 

 effect is an increase in bulk of the tissues, thus permitting us, by the sim- 

 ple expedient of observing the body weight, to draw conclusions as to 

 the influence of various foodstuffs on tissue construction. 



