262 



THE EOTHAMSTED EXPERIMENTS. 



Plan 

 adopted. 



Contin- 

 ental and 

 other ex- 

 periments. 



Details of 

 Rotham- 

 sted plan 

 of experi- 

 ments. 



Character- 

 istics of the 

 plan. 



Animals 

 experi- 

 mented 

 upon. 



that systematic feeding experiments were commenced at 

 Eothamsted. In the arrangement of them, the settlement of 

 the questions raised by the experiments and conclusions of 

 Boussingault, and by the enunciation of the theoretical views 

 of Liebig, was kept prominently in view. But the plans 

 adopted were, in some points, characteristically different from 

 those adopted by Boussingault, and even more so from those 

 which, as we shall see further on, have been generally followed 

 by subsequent experimenters. 



In Boussingault's feeding experiments he sought to ascer- 

 tain the comparative values of different foods by trials with 

 animals which were, as far as possible, maintained in an uni- 

 form condition, both as to weight and other circumstances, 

 but which were, nevertheless, living and feeding under the 

 normal conditions of such animals, for example a cow yield- 

 ing milk, or a horse performing work. A vast amount of 

 careful experiment has, however, since been devoted by others 

 to determine the food requirements of a given live-weight for 

 mere sustenance or maintenance ; that is, not only without 

 either loss or gain, but exclusively of the yield of milk, in- 

 crease in live-weight, or the exercise of force ; and then, as a 

 separate question, to determine in the case of animals feeding 

 for the production of meat, how much of the different con- 

 stituents of food is required to be supplemented to the mere 

 sustenance ration, to obtain the maximum increase for the 

 minimum expenditure of the different food-constituents. 



Our own plan was, on the other hand, in the case of ani- 

 mals fed for the production of meat, to select foods of recog- 

 nised value for such animals ; to give a fixed quantity daily, 

 of one or more, and to allow the animals to take, ad libitum, 

 of some other or complementary food ; the object being, ex- 

 cepting in certain cases for comparison, to secure that they 

 should yield normal or full increase in weight, and that the 

 results should indicate to what constituent, or class of con- 

 stituents, in the food, the actual and comparative results were 

 to be attributed. 



It will be seen that, under such a plan, the animals practi- 

 cally fixed their own consumption, according to the composi- 

 tion of the foods, and to their requirements ; and that, the 

 amounts of food, or of its various constituents consumed, 

 covered the requirements, both for mere maintenance, and for 

 the growth and fattening increase, as the case might be. It 

 was thought that results so obtained, being comparable with 

 those of actual practice, would supply important data for the 

 elucidation of the principles involved in such practice. 



Several hundred animals — oxen, sheep, and pigs — have been 

 experimented upon. In the greater number of cases, and 



