Decembeb 10, 1909] 



SCIENCE 



819 



a problem of energy supply. While a 

 small proportion of our food during the 

 earlier years of life serves to build up the 

 bodily machinery, by far the larger part 

 of it is simply the vehicle by means of 

 which chemical energy is introduced into 

 organism, to be libei-ated again as work or 

 heat in the perfonuance of the vital func- 

 tions. Briefly and crudely stated, food is 

 the fuel of the body. The ultimate source 

 of this energy, so far as we are concerned, 

 is the sun. Crops are produced by means 

 of solar radiation and food represents the 

 stored-up energy of the sun's rays. The 

 continuance of life upon the earth is con- 

 ditioned upon the ability of the plant to 

 effect this storage of energy and the den- 

 sity of population which a country can 

 support from its own resources is limited 

 absolutely by the amount of solar energy 

 which can be recovered in the form of food 

 products. 



In view of this absolute dependence on 

 solar radiation, it is a rather startling fact 

 that the larger part of the energy stored 

 in an acre of crop is contained in inedible 

 products. From one half to two thirds of 

 the organic matter of the corn crop, for 

 example, is contained in the stover and 

 cobs and about sixty per cent, of that of 

 the average wheat crop in the straw. 

 Furthermore, grain itself is not adapted 

 for direct consumption by man, but under- 

 goes various processes of preparation, giv- 

 ing rise to numerous unavailable by-prod- 

 ucts. For example, in the milling of 

 wheat, about 25 per cent, of the grain 

 passes into the offals and only 75 per cent, 

 serves for purposes of human nutrition. 

 In other words, out of the total energy 

 stored up by the grovrth of an acre of 

 wheat only about 30 per cent, serves 

 directly for the nutrition of man. Sub- 

 stantially the same thing is true in greater 

 or less degree of other food crops, while the 



grasses and leguminous forage crops which 

 play so important a role in modem agri- 

 culture are, of course, entirely useless as 

 human food. 



It is clear that as population becomes 

 denser and agriculture more intensive, it 

 will become essential to utilize the energy 

 of these by-products as completely as pos- 

 sible. When we number 500,000,000 we 

 can not afford to throw 60 per cent, of the 

 energy of the wheat crop into the manure 

 heap if it is possible to save any of it. The 

 agency for effecting this saving is our do- 

 mestic animals. They are able to consume 

 these by-product materials which man can 

 not use and to render available a portion 

 of their energy, using it in the first in- 

 stance to support their own lives, but also 

 storing up for man's use a certain part of 

 what would otherwise be a total waste. As 

 the demand for food grows more intense, it 

 will become increasingly important to so 

 husband these by-products and combine 

 them into efScient rations, and to feed 

 these rations under such conditions and 

 to such types of animals, as to save the 

 largest possible percentage of the energy 

 which they contain. 



It scarcely need be said that we are still 

 far from doing this. Our rations are too 

 often faulty and fed to inferior animals 

 under unfavorable conditions, and only a 

 short railway journey is necessary to con- 

 vince one of the enormous waste of forage 

 taking place every year, while our by- 

 product feeding stuffs compete with native 

 products in the markets of the old world. 



AVith our relatively sparse population, 

 this has hitherto been a country not only 

 of cheap food, but especially of cheap meat, 

 and we have been fond of drawing the con- 

 trast between the diet of our laborers, with 

 its abundance of animal food, and that of 

 the European laborer, and whether rightly 

 or wrongly, have attributed much of the 



