ormers, there are many other reasons which as clearly prove the
fallacy of this rule. If we were, for instance, to estimate the value
of albumen according to the tables of food equivalents which were
constructed some years ago by Boussingault and other chemists, we would
find one pound weight of it to be equivalent to four pounds weight of
oil-cake, or to twelve pounds weight of hay; yet, it is a fact that
a horse would speedily die if confined to a purely albuminous diet,
whereas hay is capable of supporting the animal's life for an indefinite
period.

It is clear, then, from what I have stated, that neither the amount of
flesh-formers, nor of fat-formers, contained in a given quantity of a
substance is a measure of its nutritive value; nevertheless it would
be incorrect to infer from this that the numerous analyses of feeding
substances which have been made are valueless. On the contrary, I am
disposed to believe that the composition of these substances, when
correctly stated by the chemist, enables the physiologist to determine
pretty accurately their relative alimentary value. Theory is certainly
against the assumption that food is valuable in proportion to its
content of nitrogen; nor has practice less strongly disproved its truth.
An illustration drawn from the nutrition of plants will make this matter
more apparent. Every intelligent agriculturist knows that guano contains
nitrogen and phosphoric acid; both substances are indispensable to the
development of plants, and therefore it would be incorrect to estimate
the manurial value of the guano in proportion to the quantity of
nitrogen it was capable of yielding. If the value of manures were
determined only by their per-centage of nitrogen--a mode by which
certain chemists still estimate the nutritive value of food--then
woollen rags would be worth more than bones, and bones would be more
valuable than superphosphate of lime. The truth is, that the analysis of
feeding stuffs and manures is sometimes of little value if the condition
in which the constituents of these substances exist be undetermined. For
example, the analysis of one manure may show it to contain 40 per cent.
of phosphate of lime, and three per cent. of ammonia, whilst, according
to analysis, another fertiliser may include 20 per cent. of phosphate of
lime, and two per cent. of ammonia. Viewed by this light solely, the
first manure would be considered the more valuable of the two, whereas
it might,