196 ON THE COAGULATION OF THE BLOOD 
It was suggested to me that perhaps it might arise from some physical change 
in the glass due to the very high temperature to which I had subjected it. It 
had been observed by Liebig that, whereas a supersaturated solution of sulphate 
of soda is, under ordinary circumstances, made to start into a crystalline mass 
by contact with a glass stirring rod, no such effect is produced by the rod if it 
is heated in the flame of a spirit lamp and allowed to cool; a result attributed 
by Liebig to some temporary physical change produced in the glass by the heat. 
Might it be, then, that the fibrine of the clot failed to shrink in consequence 
of a different molecular arrangement assumed under the influence of the glass 
altered by heat? That view, however, has been exploded; because it has 
been proved, as illustrated by some striking experiments shown at a conver- 
sazione of the Royal Society some years ago by my colleague, Professor Thomson, 
that the cause of the crystallization of the supersaturated solution of sulphate 
of soda is not the contact with the glass as such, but the accidental presence 
on the glass of minute quantities of sulphates isomorphous with the sulphate of 
soda ; and that the effect of the heat is to drive off the water of crystallization 
of those salts, and make them no longer isomorphous with it, and, therefore, 
no longer able to induce the crystallization. And so a mystery in physics was 
cleared away, and made a very simple matter. Thus the suggested explanation 
fell to the ground. 
The same absence of shrinking of the clot had been brought about by different 
means in the example which I exhibited to this Society nearly seven years ago.1 
A glass jar, not especially clean, had been purified by means of a solution of 
corrosive sublimate in 500 parts of water. Blood had been let into this jar from 
the jugular vein of a horse, under antiseptic precautions, forty-one days before ; 
and the members of the Society had the opportunity of seeing that, just as in 
the case of the flask subjected to a high temperature, the clot had not shrunk ; 
the serum had not been squeezed out of it. And although it seems unlikely 
that in the short time that elapses between the shedding of the blood and the 
commencement of shrinking of the clot under ordinary circumstances, the micro- 
organisms present could have had such an influence on the blood, yet when we 
see that two agencies so different in their nature as a high temperature and a 
solution of corrosive sublimate, but both powerfully germicidal, led to the same 
result, one is almost inclined to think that surely it must beso. No other explana- 
tion has been offered, although I know that physiologists have been much 
interested in the subject. 
If we admit that micro-organisms are the cause of the shrinking of the clot, 
and that the shrinking of the clot is the cause of its extension, it follows that 
' British Medical Journal, 1884, vol. ii, p. 803 (see p. 293 of volume ii of collected papers). 
