162 ANIMAL PHYSIOLOGY. 
the corpuscles constantly, but in the above cases and during life 
is not effective because at once removed by the vessel walls; 
while others are of opinion that the living cells composing these 
walls prevent the formation of the ferment. 
Even when injected into the blood-vessels, fibrin-ferment 
does not induce coagulation, nor does the constant death of the 
blood-cells, supposed thus to give rise to this substance, cause 
clotting. 
But the truth is, there is no necessity for all these somewhat 
artificial views, which seem to us to smack more of the labora- 
tory than of nature. 
We would explain the whole matter somewhat thus: What 
the blood is in chemical composition and other properties from 
moment to moment is the result of the complicated interaction 
of all the various cells and tissues of the body. Any one of 
these, departing from its normal behavior, at once affects the 
blood; but health implies a constant effort toward a certain 
equilibrium, never actually reached but always being striven 
after by the whole organism. The blood can no more maintain 
its vital equilibrium, or exist as a living tissue out of its usual 
environment, than any other tissue. But the exact circum- 
stances under which it may become disorganized, or die, are 
legion; hence, it is not likely that the blood always clots in 
the same way in all groups of animals, or even in the same 
group. The normal disorganization or death of the tissue re- 
sults in clotting; but there may be death without clotting, as 
when the blood is frozen, in various diseases, etc. 
To say that fibrin is formed during coagulation expresses in 
a crude way a certain fact, or rather the resultant of many 
facts. To explain: When gunpowder and certain other ex- 
plosives are decomposed, the result is the production of cer- 
tain gases. If we knew these gases and their mode of com- 
position but in the vaguest way, we should be in much the 
same position as we are in regard to the coagulation of the 
blood. 
There is no difficulty in understanding why the blood does 
not clot in the vessels after death so long as they live, nor why 
it does coagulate upon foreign bodies introduced into the blood- 
stream. So long as it exists under the very conditions under 
which it began its being, there is no reason why the blood 
should become disorganized (clot). It would be marvelous if 
it did clot, for then we could not understand how it could ever 
have been developed as a tissue at all. It is just as reasonable 
