REMARKS ON COMPOSITION OF THE BLOOD. 
729 
The proportionate quantity of the red cells to the other 
constituents of the blood has already been said to be as much 
as an eighth part. The quantity, however, is liable to much 
variation, depending on certain conditional states of the 
system. In animals of robust health it is always large, as 
also in those that are well fed and which undergo a fair amount 
of exertion and breathe a pure air. Wild animals are said to 
have a relatively increased quantity when compared with 
domesticated animals, especially such as are placed under cir¬ 
cumstances 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 blood 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 fail 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 patho¬ 
logist, and hereafter we shall see the influence these changes 
have in rendering animals susceptible 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 
connected with respiration than with nutrition, and hence 
they are sometimes spoken of as the respiratory element 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 external 
influences by which they are surrounded : hence the term 
“warm-blooded” animals. This heat is evolved in every pRrt 
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 formation 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 w hich are ever taking place in the conversion of the 
