260 



THE EOTHAMSTED EXPERIMENTS. 



Classifica- 

 tion of 

 foods. 



Applica- 

 tion of 

 Boussin- 

 gault's 

 tables. 



Import- 

 ance of 

 Boussin- 

 gault's in- 

 vestiga- 

 tions. 



Liebig's 

 work. 



of 42 per cent carbon, was supplied in the amount of each 

 food containing the nitrogen of 100 of hay. If the amount 

 were less than in 100 of hay, he calculated how much straw 

 was required to supply the deficiency, assuming straw to 

 contain 45 per cent of such matter. The final result showed, 

 not only the same amount of nitrogenous, but as much of 

 digestible non-nitrogenous substance also, as 100 of hay. If, 

 however, the nitrogen equivalent of the food contained an ex- 

 cess of digestible non-nitrogenous constituents, he did not 

 make any corresponding deduction from the ration. 



Boussingault fully recognised that food equivalents so 

 calculated are only satisfactory in comparing foods of 

 the same description, which he classified generally as fol- 

 lows : — 



1. Hays and straws. 



2. Eoots and tubers. 



3. Oily seeds. 



4. Cereal grains, leguminous seeds, oilcake, &c. 



He pointed out that when the application of the tables 

 is thus limited, they are very useful in showing how one 

 food may be advantageously substituted for another of the 

 same class, according to relative abundance, cheapness, and 

 so on. 



In conclusion in regard to Boussingault : in giving a sketch 

 of the history of the progress in our knowledge of the subject 

 of the feeding of the animals of the farm, it was only due 

 to him to give prominence to his enormous, painstaking, and 

 most conscientious labours in regard to it. This is the case, 

 independently of any direct applicability of his results and 

 conclusions at the present time, because he was essentially 

 the pioneer, and his conceptions and methods have had a 

 very marked influence on the direction of subsequent investi- 

 gations. 



It was in 1842 — that is, after Boussingault's first systematic 

 discussion of the subject, but before his second — that Liebig 

 published his work entitled Chemistry in its applications to 

 Physiology and Pathology. In it he treated of food in its 

 relations to the various exigencies of the animal body ; and, 

 apparently impressed, as was Boussingault, with the fact that 

 nitrogenous constituents were both essential and characteristic 

 of the animal body, and that they must therefore be supplied 

 in the food they consumed, and in the case of the herbivora, 

 in vegetable food-stuffs, he also, like Boussingault, indeed, 

 probably directly influenced by his results and conclusions, him- 

 self concluded that the comparative values of food-stuffs as such 

 were, as a rule, measurable by their richness in the nitrogen- 

 ous, rather than in that of the non- nitrogenous constituents — 



