st important to determine whether there are not some
substances from which the nutritive matters may not be more easily
assimilated than from others, and what proportion of each is absorbable
under ordinary circumstances. On this point no information has yet been
obtained applicable to individual feeding substances, but the
experiments of Messrs. Lawes and Gilbert have shewn the quantity of the
total food, and of each of its constituents, stored up in the fattening
animal, and a summary of their results is contained in the following
Table:--

TABLE shewing the Amount of each Class of Constituents, stored in the
increase, for 100 consumed in the Food.

+------+---------+-------------+------+------------+
| | Mineral | Nitrogenous | | Total Dry |
| | Matters | Compounds. | Fat. | Substance. |
+------+---------+-------------+------+------------+
|Sheep | 3.27 | 4.41 | 9.4 | 8.06 |
|Pigs | 0.58 | 7.34 | 21.2 | 17.3 |
+------+---------+-------------+------+------------+

Hence it appears that the pig makes a better use of its food than the
sheep, retaining twice as much of its solid constituents within the
body, from which may be deduced the important practical conclusion, that
the former must be fattened at a much smaller cost than the latter.
Looking at the individual constituents, it appears that, in the sheep,
less than one-twentieth of the nitrogenous compounds, and one-tenth of
the non-nitrogenous substances contained in the food, remain in the
body; and a knowledge of these facts tends to modify the conclusions
which might be drawn from the composition of the increase in the
fattening animal. Its influence may be best illustrated by a particular
example. If, for instance, the increase in a sheep contained its
nitrogenous and respiratory elements in the ratio of 1 to 10, it would
be totally incorrect to supply these substances in the food in the same
proportions. On the contrary, it would be necessary at the very least to
double the proportion of the former, because one-tenth of the
fat-forming elements are absorbed, and only one-twentieth of the
nitrogenous.

On further consideration, also, it seems unquestionable that the
quantity of the nutritive elements stored up must depend to a large
extent on the nature of the food and the particular state in which they
exist in it. It is probable, or at least possible, that some kinds of