692 



SCIENCE 



[N. S. Vol. XXVI. No. 673 



attention to a few well-known facts. 

 Plants can live on the dead inorganic mat- 

 ter contained in the air and soil alone. 

 They have the power of transforming it 

 into living organic matter and into the 

 more complicated combinations of which 

 their bodies are composed. Animals can 

 not live on inorganic matter alone. They 

 must have in addition the more highly 

 organized forms, which plants produce. 

 Hence the animal kingdom is dependent 

 upon the vegetable kingdom for its ex- 

 istence. 



Since animals consume plants for food, 

 it follows that the same elements which 

 occur in plants are found in the animal 

 body. In fact the same compounds that 

 occur in vegetable matter are again found 

 in the animal body, only slightly modi- 

 fied. 



Before chemistry began to shed its light 

 upon agriculture, the rearing and feeding 

 of domestic animals for human food and 

 raiment was just as empirical as the pro- 

 duction of plants. It is true, as already 

 stated, that simple observation led to many 

 good methods in actual practise, but no 

 intelligent reasons could be given for the 

 methods. The subject of animal nutrition 

 was taken up by scientific investigators 

 with as much zeal and as careful study and 

 experimentation as were expended on vege- 

 table production, and the results and data 

 obtained are sufficient to warrant an intel- 

 ligent use of the means at hand. 



The amount of time and labor expended 

 in changing the rule-of-thumb methods of 

 feeding, domestic animals into a rational 

 system is very great taken in the aggregate. 



1. The composition of every product of 

 domestic animals, the composition of every 

 part of their bodies, and the proportion of 

 these parts among themselves in forming 

 the living animals produced for various 

 purposes are known to the chemist. 



2. The proximate composition of feeding 

 stuffs of all kinds has been accurately de- 

 termined by thousands upon thousands of 

 analyses made in all parts of the world. 

 Extensive tables giving the percentage of 

 protein, fat, carbohydrates, fiber and ash 

 have been placed at the command of every 

 one engaged in this branch of agriculture. 

 But this is not all. Just as the total 

 amount of plant food in the soil is not 

 completely available for the production of 

 vegetable matter, so the proximate prin- 

 ciples just mentioned do not entirely serve 

 as nourishment for the animal body. The 

 digestibility of the various ingredients varies 

 in different plants as well as in different 

 parts of the same plant. Hence a simple 

 analysis of a feeding stuff does not always 

 determine its true food value. For this 

 reason additional investigations were found 

 to be necessary. Just as in the determina- 

 tion of the available plant food of a soil the 

 plants are brought into requisition, so here 

 experiments had to be made in connection 

 with various domestic animals in order to 

 determine the amount of these ingredients 

 which served as nourishment when taken 

 into the system. Tables giving the coeffi- 

 cients of digestion of the constituents of 

 the feeding stuffs, therefore, always accom- 

 pany the tables of analyses. In addition 

 to all this, experiments have been made 

 with domestic animals to establish the best 

 proportion and amount of these constitu- 

 ents for the purpose of maintenance and 

 development as well as for the production 

 of work, milk, flesh, fat, etc. 



3. As in the case of commercial fertil- 

 izers, here again the work of the chemist 

 controls the sale of concentrated feeding 

 stuffs, so that the purchaser of these valu- 

 able commodities, which are thrown upon 

 the market in immense quantities, is in- 

 sured against adulteration. 



With all of this information at his com- 



