GERM THEORY OF FERMENTATIVE CHANGES 319 
the finer ones floated like gossamer in the air. Here, then, was an amazing 
chemical change effected in the milk, and one of great interest with reference 
to the elaboration of mucus and other viscid secretions in the animal economy. 
On applying the microscope I found no fungus filaments, but multitudes of 
motionless bacteria, such as are represented in Plate XI m, very minute and 
delicate, and often showing a peculiarity only badly represented in the specimens 
drawn, viz. that of having one part of the organism of much higher refractive 
power than the rest. In the lower part of the glass similar bacteria were seen 
in active movement, often curiously wriggling and sometimes rotating com- 
pletely round a transverse axis. The reaction of the milk was also changed, 
distinctly reddening blue litmus paper and not affecting red. 
Next day I introduced into another of the glasses of milk a morsel of the 
viscid substance by means of a pair of mounted needles passed through the 
flame. A glass of the artificial milk above described, which had been decanted 
for seventeen days and had undergone no change, and a glass from a flask of 
Pasteur’s solution which had been prepared on the 11th of February, and 
remained brilliantly clear, were also similarly inoculated. 
In the course of two days observing a translucent layer, about a line in 
thickness, at the top of the milk in the second glass, I removed some for examina- 
tion. It was distinctly acid in reaction but uncoagulated, and when a drop 
was diffused on a glass plate the liquid was seen to be generally thin and 
turbid, but studded with transparent specks which, when touched with the 
point of a needle, could be drawn out into threads like the viscid material of 
the first glass. On applying the microscope to one of the transparent specks, 
multitudes of motionless bacteria were seen, such as are represented at 0, 
Plate XI, showing in a striking manner the peculiarity before described, of 
having their extremities of different refractive power from the rest. The thin 
turbid part, on the other hand, was a finely granular fluid in which similar 
bacteria were seen in much smaller numbers, some of them moving freely, 
while others were motionless, the latter being each surrounded with a trans- 
parent halo of greater or less extent as is shown at # and g, Plate XI, and in 
some cases, the transparent areas surrounding different bacteria were confluent. 
These were evidently miniatures of the transparent specks visible to the naked 
eye ; and they seem to me beautiful examples of a change effected by bacteria in 
the surrounding medium, whether due to vital action of the organism or to some 
substance (a so-called chemical ferment) emitted from it during life or after death. 
The moving bacteria, it is to be remarked, had no transparent area around 
them, nor were they able to penetrate those that surrounded the motionless 
ones, proving the substantial character of the latter. 
