On the Composition of Animals slaughtered as Human Food. 291 



to be found iu the primary action of zinc upon iodide of etliyle, — 



2(C, H^ I) + 2Zn= g^ |4 + 2Zn I, 



■whilst the secondary products are derived from the decomposition of 

 iodide of ethyle by zinc-ethyle, — 



C,H,I + ZnC,H,=^*g^| +C,H,+ZnI. 



"Experimental Inquiry into the Composition of some of the 

 Animals fed and slaughtered as Human Food." By J. B. Lawes, 

 Esq., F.R.S., F.C.S., and J. H. Gilbert, Ph.D., F.C.S. 



After alluding to the importance of the chemical statistics of 

 nutrition in relation to physiology, dietetics, and rural economy, and 

 explaining that the branch of the subject comprehended in the pre- 

 sent paper is that of Animal Composition, the authors proceed in 

 the first place to state the general nature of their investigations, and 

 the manner in which they were conducted. 



To ascertain the quantitative relations, and the tendency of deve- 

 lopment, of the different parts of the system, the weights of the 

 entire bodies, and of the several internal organs, also of some other 

 separated parts, were determined in several hundred animals — oxen, 

 sheep, and l)igs. 



To determine the ultimate composition, and in a sense the proxi- 

 mate composition also, of oxen, sheep, and pigs, and to obtain the 

 results iu such manner that they might serve to estimate the pro- 

 bable composition of the Increase whilst fattening, was a labour 

 obviously too great to be undertaken with a large number of ani- 

 mals. Those selected were — a fat calf, a half-fat ox, a moderately 

 fat ox, a fat lamb, a store or lean sheep, a half-fut old sheep, a fat 

 sheep, a very fat sheep, a store pig, and a fat pig. 



It is to the methods and the results of the analysis of these ten 

 animals, to the information acquired as to the quantitative relation of 

 tlie organs or parts in the different descriptions of animal, and their 

 relative development during the fattening process, and to the appli- 

 cation of the data tbus provided, that the authors chiefly confine 

 themselves in tbe present paper. 



The analyses of the ten animals were planned to determine the 

 actual and per-ceutage amounts — of water, of mineral matter, of 

 total nitrogenous compounds, of fat, and of total dry substance — ^in 

 the entire bodies, and in certain individual and classified parts of 

 the animals. The water, and mineral matter, were for the most part 

 determined in each internal organ, or other separated part. But, to 

 confine the labour within reasonable limits, and to facilitate as far as 

 possible the j)crcej)tion of the practical and economic application of 

 the results, tlie other constituents enumerated are given in — 



1st. The collective "carcass" parts; that is, the frame with its 

 covering of flesh UiiJ fat, which comprise the most important por- 

 tions sold as human food. 



2nd. The collective "offal" parts; including the whole of the 



