338 ON THE NATURE OF FERMENTATION 
remarkable fact that this blood-clot has not undergone any contraction. One 
of the earliest things that your professor of physiology will have to teach the 
junior students will be that blood, after coagulation, contracts ; that the fibrine 
of the coagulum shrinks and the serum is pressed out. But here no such thing 
has taken place. There has been no shrinking of this clot, no pressing out of 
the serum, and I venture to say that there is no one here—at least I think it is 
unlikely that there is any one here except myself—who has seen such a pheno- 
menon, illustrating how, when the most familiar objects are placed under new 
circumstances, the most unexpected results may arise. Now, this is a matter 
of very considerable interest with reference to the behaviour of blood-clots 
inside the body in wounds and so forth. However, that is not a point on which 
I wish to dwell on the present occasion.t The point to which I wish to draw 
your special attention is, that this blood, although it has been six weeks in this 
glass, without any close fitting of the glass shade or the glass cap, and therefore 
with free opportunity for the access of the gases of the atmosphere, has not 
putrefied. The air in the glass shade is perfectly sweet, perfectly free from 
odour. 
Now, gentlemen, this, without going further, is a very important matter. 
It proves that the blood has no inherent tendency to putrefaction. It further 
proves that the oxygen of the air is not able to cause the blood to putrefy, as 
used to be supposed. There was a time—the effect is still seen to a certain 
extent—when the dark venous colour of this blood-clot gave place to the crimson 
colour of arterial blood in a gradually deepening band from above downwards. 
We still see some of the red colour remaining, though now the converse effect 
has begun to take place. That florid redness, gentlemen, showed that the 
oxygen of the air was in reality acting upon the blood, yet it did not putrefy. 
Now, if I were to take a little morsel of already putrefied blood, say, upon the 
end of a needle, and touch with it this clot of blood, putrefaction would, in the 
course of a very short time, spread throughout the mass. Exactly as in the 
case of alcoholic fermentation under the influence of the yeast plant would the 
fermentation spread. 
Putrefaction, then, is a fermentation, a true fermentation, characterized 
by the power of self-multiplication of the ferment. Then, gentlemen, if we 
examine microscopically, we find in the putrefying blood, as we found in the 
fermenting grape-juice, microscopic organisms, termed bacteria from their rod- 
shape, which we have represented in this diagram on the same scale as we 
had the yeast plant ; of different sizes, but all very much more minute than 
* I desire to guard myself against being supposed to express any opinion here as to the cause of 
this phenomenon, 
ee 
Ti RE Bc ith tl lat Natta ci 
aN iad 
