r to that employed by Pettenkofer in his experiments on
respiration. This apparatus, which was made at the expense of the King
of Bavaria, cost nearly L600.

_Value of Manure._--It is a complication in the question of the
economic feeding of the farm animals that the value of their manure
must be taken into account. Of the three classes of food constituents,
two--the mineral and nitrogenous--are recoverable in the animal's body
and manure; the non-nitrogenous is partly recoverable in the fat.
I shall take the case of a sheep, which will consume weekly per 100
lbs. of its weight, 12 lbs. of fat-formers, and 3 lbs. of flesh-formers.
Twelve per cent. of the fat-formers will be retained in the _increase_,
but the rest will be expended in keeping the animal warm, and the
products of its combustion--carbonic acid and water--will be useless to
the farmer. It is, therefore, desirable to diminish as much as possible
the combustion of fatty matter in the animal's body; and this is
effected, as I have already explained, by keeping it in a warm place.
Of the flesh-forming substance only five per cent. is retained in the
increase, the rest is partly consumed in carrying on the movements of
the animal--partly expelled from its body unaltered, or but slightly
altered, in composition. The solid excrement of the animal contains
all the undigested food; but of this only the mineral and nitrogenous
constituents are valuable as manure. The nitrogen of the plastic
materials which are expended in maintaining the functions of the body is
eliminated from the lungs, through the skin, and by the kidneys--perhaps
also, but certainly only to a small extent, by the rectum.

The food consumed by an animal is disposed of in the following way:--A
portion passes unchanged, or but slightly altered, through the body;
another part is assimilated and subsequently disorganised and ejected;
the rest is converted into the carcass of the animal at the time of its
death. The undigested food and aliment which had undergone conversion
into flesh and other tissues, and subsequent disorganisation, constitute
the excrements, or manure, of the animal. The richer in nitrogen and
phosphoric acid the food is, the more valuable will be the manure; so
that the money value of a feeding stuff is not determinable merely by
the amount of flesh which it makes, but also, and to a great extent,
by the value of the manure into which it is ultimately converted.

Corn and oil-cak