THE BLOOD. 
485 
life. So that neither of these causes will account for the coagu¬ 
lation, though experiments constrain us to admit that they both 
seem somewhat influential. 
Other circumstances and agents also affect the coagulation. 
It will congeal sooner when drawn from a small orifice, or al¬ 
lowed to trickle down the side of the vessel or the animal’s neck, 
than under opposite circumstances. Various chemical agents 
thrown into the vessel will effect its coagulation at once: such 
are certain of the neutral salts, acids, alcohol, and alum. 
Of the various conjectures and opinions that have been framed 
to account for this miraculous change in the blood, none seems 
so well worthy our attention as that left us by the famed John 
Hunter. He ascribed the coagulation to the presence of a vital 
principle in the fluid. To use his own words: “ To conceive 
that blood is endowed with life while it is circulating, is, perhaps, 
carrying the imagination as far as it can go; but the difficulty 
arises merely from its being a fluid, the mind not being accus¬ 
tomed to the idea of a living fluid He next proceeds to shew, 
“ that organization and life do not depend in the least on each 
other; that organization may arise out of living parts and produce 
action, but that life can never rise out of, or depend on, organ¬ 
ization. ” And, in the third place, he evinces, by many ingenious 
facts and experiments, a striking analogy between the coagula¬ 
tion of the blood and the contraction of muscular fibre. Animals 
killed by lightning or electricity have not their blood coagulated, 
nor their muscles contracted. Those that are hunted to death, 
or, in fact, in any way suddenly extinguished, exhibit the same 
coincident phenomena; also their bodies are more disposed to 
run into putrefaction. From all which evidence, Mr. Hunter 
concluded that blood, in a living body, was possessed of what 
he termed a materia vita diff usa. 
Dr. Bostock objects to the Hunterian doctrine on the score 
that, even were “ the life of the blood fully established, it would 
not off er any explanation of the cause of its coagulation ; for the 
same difficulty (adds he) still remains, in what manner the pre¬ 
sence of life operates, so as to produce either the coagulation of 
the blood or the contraction of the muscles.” But this remark is 
one that would equally apply to all vital phenomena. The Doc¬ 
tor gives it as his opinion that, u perhaps, the most obvious and 
consistent view of the subject is, that the fibrin has a natural dis¬ 
position to assume the solid form , when no circumstance (either 
chemical or mechanical) prevents it from exercising this inherent 
tendency.” 
