CH. XLI.] METABOLISM OF PROTEIN 625 



argument than the one so often used when the instinctive habits of 

 past centuries of adults are appealed to. 



We may also draw a useful lesson from disease. In the modern 

 treatment of consumption, the open-air cure is combined with a steady 

 process of generous feeding ; in certain cases of nervous breakdown, 

 an important part of the " rest cure " is the providing of abundant 

 and appetising meals. One can hardly doubt that much of the 

 benefit noticeable in both classes is due to the "reserve energy" 

 provided, enabling the body more fully to grapple with the malady. 

 "Reserve energy" may be objected to as a vague phrase which, 

 though comforting to those who use it, is nevertheless very difficult 

 to explain. There is a good deal of reason in such an objection, for 

 " reserve force " is difficult to define clearly. We have, for instance, 

 no knowledge of any storage places for protein, in the same way in 

 which the liver and adipose tissue act as storehouses for carbohydrate 

 and fat respectively. But it is an undoubted factor all the same ; 

 many people have more of it than others ; and this " stamina," as it 

 is sometimes called, is a lucky possession for those who have it. 

 Research on immunity has, however, shown us that this is in part due 

 to the condition of our leucocytes, and the opsonic power of the 

 blood-plasma (see p. 476). It may be that it is in this direction 

 among others, that the abundance of protein food may assist us in 

 repelling disease. Each leucocyte may not require much in the 

 way of repair every day, but it is more likely to get this " stitch in 

 time" if there is an abundant supply of repairing material 

 available. 



Rubner has called attention to what he terms the specific dynamic 

 action of food-stuffs. Weight for weight, fat yields more heat when 

 burnt than protein does, and outside the body it is more easily 

 combustible than either protein or carbohydrate. Inside the body 

 it is just the reverse; proteins are the most readily burnt of any 

 food material, and fats the least. In other words, proteins (and the 

 same is true for arnino-acids) have a specific value in stimulating 

 metabolism, and so leading to an increase of oxidation in the 

 body. Some of the subjects of Chittenden's experiments suffered 

 intensely from the cold in the winter, and this use of protein must 

 not be lost sight of in settling the right amount which we should 

 take in our daily food. 



Some attempt has been made to determine which of the protein 

 cleavage products, or Bausteine, to use the German term, are specially 

 valuable in the body, either for the synthesis of tissue protein, or, as 

 Hopkins has suggested, for the formation of the special hormones or 

 chemical messengers of the body, such as adrenaline. 



Recent research has established the fact that one of the important 

 building stones for these purposes is phenyl-alanine, and its near 



2 R 



