Now in view of our absolute dependence on solar radiation, it is a rather startling fact that but the smaller part of the energy stored up in the farmer's crops is directly available for man's use. Of that of the wheat crop, for example, fully sixty per cent, is contained in the straw and another 10 per cent, is rejected in the process of milling as bran and other by-products. In other words, only about 30 per cent, of the energy stored in an acre of wheat is directly available for human nutrition. Much the same thing is true of most other food crops, while the grasses and clovers, so important in all systems of agriculture, are, of course, entirely unavailable as food for man. Hitherto, our enormous surplus of food products has served to obscure the significance of this fundamental fact. Not only have we been able to export vast quantities of breadstuffs to less fortunate lands, but we have used other millions of bushels of edible products, especially corn, as food for domestic animals. America has been a country of cheap animal food—meat, eggs, milk, butter, cheese, etc.—and we have been fond of drawing the comparison between the abundant meat supply of our working classes and its comparative scarcity in the diet of the European laborer and, rightly or wrongly, have attributed much of the greater industrial efficiency of our workmen to this difference in diet.
But we are rapidly approaching an economic limit to the production of meat from edible grains. Such a conversion is an exceedingly wasteful process. Of the solar energy stored up in a bushel of corn, less than 3 per cent, is recovered in the edible portion of the carcass of the steer to which it is fed, while even in pork production this percentage scarcely rises to more than 16, and in milk production to about 18, and similar losses are observed in all branches of animal production. In other words, the stockman who feeds his animals on grain is expending energy available for human use as fuel for his animal machines for the sake of recovering a small fraction of it in higher priced and more palatable products, a process which can hardly fail to remind one of the reputed origin of roast pig. So long as our food supply was vastly in excess of our needs, such practises were doubtless economically justifiable. To the solitary hunter in the primeval forest it was a matter of comparative indifference whether he made his camp fire of underbrush or of the best grade of timber, but with lumber at its present price, the mill owner can afford only sawdust and refuse to feed his fires. In the past, speaking broadly, our meat production has consisted to a large extent in the exploitation of our food resources. There has been a choice between producing bread or meat, and the improvements in stock husbandry have been largely in the direction of more profitable exploitation. In the near future, we shall have to reverse this attitude and study the conservation of the food supply. Not much longer can we continue to take the children's bread and cast it to the brutes. If our
