hat the blood of an inhabitant of the arctic circle has a
temperature as high as that of the native of the South, who lives in so
different a medium. This fact, when its true significance is perceived,
proves that the heat given off to the surrounding medium is restored
within the body with great rapidity. This compensation takes place more
rapidly in winter than in summer, at the pole than at the equator.

"Now in different climates the quantity of oxygen introduced into the
system of respiration, as has been already shown, varies according to
the temperature of the external air; the quantity of inspired oxygen
increases with the loss of heat by external cooling, and the quantity
of carbon or hydrogen necessary to combine with this oxygen must be
increased in like ratio. It is evident that the supply of heat lost by
cooling is effected by the mutual action of the elements of the food and
the inspired oxygen, which combine together. To make use of a familiar,
but not on that account a less just illustration, the animal body acts,
in this respect, as a furnace, which we supply with fuel. It signifies
nothing what intermediate forms food may assume, what changes it may
undergo in the body, the last change is uniformly the conversion
of carbon into carbonic acid and of its hydrogen into water; the
unassimilated nitrogen of the food, along with the unburned or
unoxidized carbon, is expelled in the excretions. In order to keep up
in a furnace a constant temperature, we must vary the supply of fuel
according to the external temperature--that is, according to the supply
of oxygen.

"In the animal body the food is the fuel; with a proper supply of oxygen
we obtain the heat given out during its oxidation or combustion."(3)

BLOOD CORPUSCLES, MUSCLES, AND GLANDS

Further researches showed that the carriers of oxygen, from the time of
its absorption in the lungs till its liberation in the ultimate tissues,
are the red corpuscles, whose function had been supposed to be the
mechanical one of mixing of the blood. It transpired that the red
corpuscles are composed chiefly of a substance which Kuhne first
isolated in crystalline form in 1865, and which was named haemoglobin--a
substance which has a marvellous affinity for oxygen, seizing on it
eagerly at the lungs vet giving it up with equal readiness when coursing
among the remote cells of the body. When freighted with oxygen it
becomes oxyhaemoglobin and is red in color; when fr