PHYSIOLOGY OF THE BLOOD. 
393 
to and by each other, in consequence of which more serum is 
forced out; on the contrary, if received into a shallow, wide 
vessel, where the particles are spread over a larger surface, it is 
longer in solidifying, and does not afford so firm a clot, from 
the serum remaining more mixed. Stirring the blood also retards 
coagulation. The admixture of a solution of muriate of soda 
has the same effect. 
John Hunter observes, if there was not a mechanical force, as 
abovenamed, the serum would remain mixed from capillary attrac- 
tion, as in a sponge; whereas the blood requires some days for 
complete coagulation or contraction, the clot becoming smaller 
and firmer from more serum being forced out. As the colouring 
matter is specifically heaviest, it gravitates to the bottom, in 
doing which it is arrested in some measure by the coagulation of 
the other component parts. As the blood is longer in solidifying, 
more will be precipitated, and vice versa. 
The temperature of the blood varies from 98° to 100° and 102°, 
while in the living subject. 
The general time for coagulation of the blood in the human 
subject varies from ten to fifteen minutes, and in the horse from 
fifteen to twenty-five. 
The chemical composition of blood in a healthy state, as given 
bv Berzelius, is as follows : — 
In 1000 parts. 
Water - 780.145 
Fibrine - 2.100 
Colouring matter ______ _ 133.000 
Albumen 65.090 
Crystalline fatty matter 2.430 
Oily matter - - 1.310 
Extractive matter soluble in water and alcliol - 1.790 
Albumen combined with soda 1.265 
Chloride of sodium ------- ) 
Chloride of potassium - > 8.370 
Carbonates, phosphates, and sulphates of potass and soda J 
Carbonates of lime and magnesia } 
Phosphates of lime, magnesia, and iron _ - _ _ > 2.100 
Peroxide of iron ; 
Loss - 2.400 
1000.000 
In addition to the consituents just enumerated, a volatile prin- 
ciple has been found to exist peculiar to each species of animal. 
This principle, in its odour resembles the perspiration, both in 
the human subject and the horse ; in the ox, that of a cow-house. 
It may be disengaged by mixing sulphuric acid with the blood. 
VOL. IX. 3 F 
