468 



REPORT OF COMMISSIONER OF FISH AND FISHERIES. [26] 



The 'protein 

 of food 



drates. Vegetable foods, as wheat, potatoes, &c., contain less protein 

 and consist largely of stare]), sugar, cellulose, and other carbo-hydrates. 



Functions of nutrients.— The different nutrients have different offices 

 in nourishing- the body, in building up its tissues, repairing- its wastes, 

 and serving as fuel to produce animal heat and muscular and intellect- 

 ual energy. The chief part borne by each in nutrition is shown below : 

 C forms the (nitrogenous) basis of blood, muscle, connective 

 tissue, &c. 

 is transformed into fats and carbo-hydrates, and stored 



as such in the body. 

 is consumed for fuel. 



TJie fats i are stored as fat. 

 of food \ are consumed for fuel. 

 The carlo- hy- i are transformed, into fat. • 

 drates of food \ are consumed for fuel. 



In classifications formerly maintained and frequently met with still, 

 the protein compounds were regarded as the "flesh-formers" and the 

 sources of muscular energy, while the carbo-hydrates and fat were looked 

 upon a "fat-formers" and "heat-producers." A vast deal of painstak- 

 ing research, however, has shown that these distinctions were not cor- 

 rectly drawn. The albuminoids are flesh-formers, it is true; indeed, 

 flesh, *. e., muscular and other nitrogenous tissue, according- to the 

 nearly unanimous testimony of the most trustworthy experimenters, is 

 made from the nitrogenous constituents of the food exclusively. Bat 

 the balance of testimony is decidedly against the production of muscu- 

 lar energy by nitrogenous compounds exclusively or mainly. Each of 

 the three groups of nutrients probably shares, directly or indirectly, in 

 this function. So, too, it appears that the combustion which produces 

 animal heat is not confined to the carbo-hydrates and fats, but the pro- 

 tein compounds, or the products of their decomposition, are also used 

 for this purpose. Again, the production of fat in the body was formerly 

 ascribed to the fats and carbo-hydrates alone. The view was held at 

 the same time, and is still maintained, by some physiologists, that the 

 carbohydrates cannot be transformed into fats, and that a very large 

 part of the fat of the body is formed from the disintegration of the albu- 

 minoids. The weight of evidence to-day is decidedly in favor of the as- 

 sumption that all three of the great classes of nutrients in our foods — 

 the albuminoids, the carbohydrates, and the fats — are transformed into 

 fat, and that the fat thus formed is consumed, either before or after 

 beiiig stored as body-fat. 



It appears, then, that protein is the most important constituent of 

 our food, because, while it performs the functions of each of the other 

 two chief nutrients in being transformed into fat and in being consumed 

 for fuel, it has a most weighty office of its own in forming the basis of 

 the blood and in building up the muscular and other nitrogenous tis- 

 sues, an office which no other nutrient can perform at all. And, as we 



