214 
On the Composition of the Blood. 
and breatlio a pine air. Wild animals are said to liave a rela- 
tively increased quantity when compared with domesticated 
animals, especially such as are placed under circumstances the 
very opposite to those we have just named. 
Dr. Carpenter, in his ' Manual of Physiology,' says that it 
has been ascertained that even sex has its influence over the 
number of the red cells — the l)lood of the male possessing a larger 
proportion than the blood of the female. He also states that, 
estimating 1000 parts of the blood of a male to contain 132 
parts of red cells, this quantity may rise to 186, or fall to 110, 
without the manifestation of disease ; and that in the female, 
taking the average at 120, it also may rise to 167, or fall to 71, 
without producing any untoward results. Facts of this kind are 
of the first importance to the pathologist, and hereafter we shall 
see the influence these changes have in rendering animals sus- 
ceptible to diseases which specially affect the blood ; and that, 
while they point to the means which ought to be adopted for the 
prevention of disease, they render distinct also those which 
should be had recourse to for the restoration of animals afflicted 
therewith. 
Important as the red cells may be in maintaining the health of 
an animal, they are evidently in so doing more immediately con- 
nected with respiration than Avith nutrition, and hence they 
are sometimes spoken of as the respiratory clement of the blood. 
Their chief use is thus shown to be that of preserving the heat 
of the body. It is well known that all mammalian animals 
possess a power of maintaining a heat of their own, equal to 
about 99^ of Fahrenheit, independent of the external influences 
by which they are surrounded : hence the term " warm-blooded " 
animals. This heat is evolved in every part of the organism, and 
is chiefly due to the union which is effected between the oxygen 
of the atmospheric air and the carbon of the system, leading to 
combustion, with its necessary evolution of heat and the forma- 
tion of carbonic acid gas. A second cause of animal heat is to 
be found in the union of oxygen with the hydrogen of the system, 
forming watery vapour. By some it is likewise considered that 
electricity plays a not unimportant part in the production of the 
heat of the body, while others have attributed a portion of it to 
the changes which are ever taking place in the conversion of the 
fluids into solids in the building up the frame. The latter, how- 
ever, would appear to be quite equalised by the reconversion of 
the solids into fluids, which is as continuously being effected. 
The red cells are the chief conductors of oxygen into the 
system, as they are also the conveyors of the carbonic acid out 
of it ; and in order to perform these essential offices, it is first 
necessary that they be brought into tolerably close contact with 
