SOME OF THE ANIMLiLS FED AND SLAUGHTEEBD AS HUMAN FOOD. 627 
body of the slaughtered animal. With the decrease in the proportion of bone, moreover, 
as well as the small accumulation of soft nitrogenous parts, we should also expect the 
percentage of mineral matter in the increase to be very small. 
Section YII.— ESTIMATED COMPOSITION OF THE INCEEASE IN WEIGHT OF 
FATTENING ANIMALS. 
The first and most obvious application of the data provided in the preceding sections, 
is, to employ them as a means of estimating the composition of the increase in weight of 
an anunal whilst passing fcom one given point of progress to another — as distinguished 
from the actual composition of the entire body, or its several parts, as furnished by 
analysis at any one fixed period. So far as the analysed fat Pig is concerned, the result 
of such a calculation has been already given elsewhere*. It will be interesting, however, 
to extend the application to numbers of such animals, and also to the equally, or even 
more important animals of the farm — Oxen and Sheep. 
It is obvious, that provided we know the exact composition ot an animal when it 
weighs any given weight, say 100 lbs. — and again, when, after fattening, it has reached 
another v’eight, say 150 lbs. — nothing would be easier than to calculate the actual and 
the percentage composition of the 60 lbs. that has been gained. By deducting the 
amount of the respective constituents in the 100 lbs. weight, from the amount of the 
same in the 150 lbs., we should at once ascertain the actual amount of each in the 50 lbs. 
of increase. The calculation of the jgercentage composition of the increase would then 
of course be a very simple matter. The practical difficulty obviously rests on the fact, 
that we cannot know the exact composition of a fattened animal at the time it was put 
upon fattening food, or when it had reached any given pre\ious weight. 
In the case of the store and fat Pigs which were analysed, the two animals selected 
for experiment were of the same breed and age — indeed of the same litter ; of very nearly 
equal weights ; and, so far as competent judges could decide, as nearly as possible alike 
in all other particulars. One of these animals was killed at once in the store condition, 
and its composition determined. Of the other, the exact increase in weight from this 
store or lean to the fat condition, as well as the amount and the composition of the food 
it consumed in gaining it, is known ; as also is its composition in the fattened state. The 
application of the data in the manner above supposed, is likely therefore to lead to a 
pretty trustworthy estimate of the composition of the increase of this particular fatten- 
ing Pig. 
Unfortunately, equally parallel data are not available for calculating the composition 
of the increase of the other fattened animals analysed. This is the more to be regretted, 
since, from the results of the Pigs it would appear, that data of this kind, if obtained 
under duly considered circumstances, are much more directly applicable to the determi- 
nation of the composition of increase, than we had pre-supposed would be the case. In 
1 ustration of the inapplicability of the data provided in regard to the other descriptions 
* Eeport of the British Association for the Advancement of Science for 1852. 
3 z 2 
