SCIENTIFIC FARMING AT ROTHAMSTED. 393 



Among the many important results obtained in the experiments at 

 Rothamsted, the data furnished for estimating the relative value of 

 barn-yard manures are of particular interest. The essential constitu- 

 ents of barn-yard manure, or those having a commercial value, are 

 nitrogen, potash, and phosphoric acid, which are of course derived 

 from the feed consumed by the animals making the manure. The 

 composition of the food being known, the percentage of its several 

 constituents that are voided in the manure may be estimated from the 

 data obtained in these experiments, so that the relative value of the 

 manure produced from different articles of food can be determined 

 with sufficient accuracy for all practical purposes. From the results of 

 the Rothamsted feeding experiments, we can not avoid the conclusion 

 that the cereal grains and the highly nitrogenous linseed and cotton- 

 seed cakes have essentially the same value as fattening foods, and that 

 there is but little, if any, difference in the feeding value of timothy 

 and clover hay. When the production of manure is concerned, how- 

 ever, the clover has a much higher value than timothy, and the linseed 

 and cotton-seed cakes are worth very much more than the cereal grains. 

 That is to say, the digestible and available non-nitrogenous constitu- 

 ents of the food determine its nutritive value, provided always the 

 moderate required supply of nitrogenous materials is present, and the 

 comparative manurial value is determined by the nitrogenous constitu- 

 ents. A variety in the ration would undoubtedly be desirable for 

 nutritive purposes, as the best results can not be obtained with any 

 single article of diet. 



From the facts already presented it appears that a large proportion 

 of the increase of fattening animals, in many cases more than two 

 thirds, is fat. It was formerly supposed that the fat of animals was 

 derived from the fatty materials in the food, but this source was found 

 to be entirely inadequate. The non-nitrogenous constituents of the 

 food the carbo-hydrates were then quite naturally looked upon as 

 the source from which the fat was elaborated ; but afterward Pro- 

 fessors Voit and Pettenkofer insisted that the fat of animals was almost 

 exclusively formed from the nitrogenous constituents of the food. In 

 experiments with pigs, which are evidently the most suitable animals 

 for experiments relating to the formation of fat, Drs. Lawes and Gil- 

 bert conclusively show that, with foods in which the ratio of the ni- 

 trogenous to the non-nitrogenous constituents was a suitable one for 

 fattening purposes as in Indian corn and barley a large proportion 

 of the fat in the stored-up increase must have been produced at the 

 expense of the non - nitrogenous constituents. There was also evi- 

 dence that the nitrogenous constituents of the food, when in excess, 

 might replace the carbo-hydrates, to some extent, in the formation 

 of fat. 



The analysis of the entire bodies and parts of the ten animals made 

 at Rothamsted furnish some interesting data in regard to the compo- 



