FOOD, AND THE DEVELOPMENT OF MAN. 593 



combioed. Blood-formers, heat-producers, and nutritive salts, are not 

 separately foods, but only factors of food, each as indispensable for 

 the vital processes as air and water, but each incapable by itself of 

 supporting life. One cannot live on albumen alone or on fat alone. 

 Without lime-phosphate no bone would be formed, no matter how 

 much pure albumen and fat we ate ; and without albumen no muscular 

 tissue would be formed, though we were to gorge ourselves with sugar 

 and salt ; finally, without fat, no brain. But we properly enough give 

 the name of foods to meat, milk, and bread, for in them all the three 

 conditions are present. 



Fortunately, these nutritive principles are found by no means 

 sparingly distributed throughout Nature; under the most varied 

 forms they occur in almost every food-stuff used by man. We not 

 only find the blood-formers in the shape of fibrine in the blood and 

 muscles of animals, of albumen in eggs, of casein in milk, of lime and 

 areolar tissue in cartilage, sinew, and skin, but also in the vegetable 

 kingdom ; we discover them in the gluten of grains, in the legumine of 

 pulse, in the vegetable albumen of sundry roots, leaves, and fruits. 

 Heat-producers are furnished, not only by the animal kingdom in its 

 fats, but by plants also. Sundry seeds give a small quantity of oil, 

 but the principal supply of heat-producing elements derived from 

 the vegetable world appears in the shape of starch, gum, and 

 sugar — substances which, during the process of digestion, are trans- 

 formed into fats, and therefore may replace the latter. Finally, 

 we have salts in the water we drink, and more abundantly in 

 nearly every animal and vegetable substance we consume. Hence, 

 it might seem to be an easy thing to find wholesome food, as though 

 one had only to seize blindly the store of food offered by Xature, 

 in order to get all that our organism requires to keep it vigorous. 

 But it is not to be forgotten that, while the nutritive elements 

 make up the losses of the organism, and renew the body, as 

 it were, still they must be taken in certain definite proportions. 

 Now, in Nature they are not distributed in any such proportion. 

 There the greatest diversity is found ; one food-stuff consists princi- 

 pally of blood-formers, another of heat-producers ; this one contains 

 only one of the nutritive salts, that one, another. If, then, we let 

 chance decide in this matter, it might easily happen that we would 

 take one element in excess, while we took none at all of another. If 

 this were the case again and again, or permanently, the organism must 

 suffer or perish utterly ; for, suppose only a single organ to be im- 

 properly nourished, i. e., to receive food insuflicient to make up its 

 losses, the check given to this one will affect all the rest. Science 

 can now pretty accurately determine the composition of every article 

 of food, and hence its contents of the various nutritive principles. 

 This is done by chemical analysis. Chemical analysis, however, is of 

 little assistance to us in determining accurately the constituents of 

 VOL. v.— 38 



