58 Messrs. J. B. Lawes and J. H. Gilbert on Food in its 



sition, the quantity consumed being weighed. In some cases a 

 single description of food only, or a mixture of several descrip- 

 tions in known proportions, was given ad libitum, but weighed ; 

 and in others, several descriptions of food were allowed, each 

 separately, ad libitum, but weighed. It will be seen that in this 

 way great variation in the amount and proportion of the nitro- 

 genous and non -nitrogenous constituents supplied was attained, 

 whilst the animals, according to the nature of the food within 

 their reach, fixed for themselves the limit of their consumption. 

 All such comparative experiments were conducted for many 

 weeks, or even for several months, consecutively, and the weights 

 of the animals themselves were determined at the commence- 

 ment, at stated periods during the progress, and at the conclu- 

 sion of the experiment *. 



To determine the character and composition of the gross in- 

 crease in live-weight, the weights of the individual internal 

 organs and of other separated parts of several hundred animals 

 of different descriptions and in different conditions as to age, 

 maturity, and fatness were taken; whilst in some carefully- 

 selected cases the total amounts of fat, nitrogenous substance, 

 mineral matter, and water were determined-}-. 



It is obvious that in the case of fattening animals, the amount 

 of food consumed in relation to a given body-weight within a given 

 time will be regulated, not only by the demands of the system 

 for the support of respiration, perspiration, &c, and for the repair 

 of normal waste of nitrogenous substance, but also by the addi- 

 tional requirements for growth and increase ; whilst, on the other 

 hand, the amount required to be consumed for the production of 

 a given amount of increase will, in its turn, include that due to 

 the demands of the system for respirable and perspirable matter 

 and the repair of the waste of nitrogenous substance. Whether, 

 however, the experimental results were calculated so as to show 

 the amount consumed per 100 lbs. live-weight per week, or to 



* " On the Composition of Foods in relation to Respiration and the 

 Feeding of Animals," Report of the British Association for the Advance- 

 ment of Science for 1852. " Agricultural Chemistry : Sheep-feeding and 

 Manure," part 1, Journ. Roy. Ag. Soc. Eng. vol. x. parti, 1849. " Reports 

 of Experiments on the Comparative Fattening Qualities of different Breeds 

 of Sheep," ibid. vol. xii. part 2, 1851 ; vol. xiii. part 1, 1852; vol. xvi. part 1, 

 1855. "Agricultural Chemistry : Pig Feeding," ibid. vol. xiv. part. 2,1853. 

 "On the Equivalency of Starch and Sugar in Food," Rep.Brit.Assoc.for]854. 



t " Experimental Inquiry into the Composition of some of the Animals 

 Fed and Slaughtered as Human Food," Phil. Trans, part 2, 1859 ; also Pro- 

 ceedings of the Royal Society, vol. ix. p. 348. " On the Composition of 

 Oxen, Sheep, and Pigs, and of their Increase whilst Fattening," Journ. 

 Roy. Ag. Soc. Eng.vol.xxi. part 2, 1860. "On the Chemistry of the Feeding 

 of Animals for the production of Meat and Manure," Proc. Roy. Dub. Soc. 

 March 31, 1864. 



