GERM THEORY OF FERMENTATIVE CHANGES 323 
and active state for the second time. For precisely the same series of changes of 
the organism was then repeated, as is sufficiently shown by the sketches, Plate XI, 
August 15, 18, and 20. I dwell upon these circumstances because they afford 
an example of modification of bacteria under different conditions of the same 
medium, and also an instance of branching, which has been spoken of by Cohn 
in his recent work as something altogether foreign to this class of organisms.! 
I also venture to hope that facts like these will tend to give the reader addi- 
tional confidence in the trustworthiness of the mode of investigation. 
One other circumstance with regard to Bacterium No. II seems deserving 
of mention. As already stated, when introduced into a glass of boiled milk, 
it grew rapidly, having after three days the appearances shown in Plate XI, Milk, 
August 18, with active movement. There was, however, up to this time no 
change in the aspect, odour, or reaction of the milk. But in the course of a few 
days the upper part of the liquid assumed a peculiar golden-yellow tint, and 
a fortnight after inoculation the appearance was almost as if the yolk of a ban- 
tam’s egg were floating on the surface, while there was also some similar yellow 
material deposited at the bottom of the glass, and the main body of the milk 
had assumed a cream colour. The reaction was now distinctly though not 
strongly acid, but the glass shade had no sour smell, a very faintly urinous 
odour being the only one perceptible. The main body of the milk was a very 
soft coagulum, but the upper part was a thin, transparent liquid, the bright 
yellow material being deposited at the junction of the two. On examining 
a portion of the yellow substance with the microscope, I could discover nothing 
but a mass of motionless but unbranched bacteria such as are shown in Plate XI, 
September 1, and I could only conclude that the bacteria were themselves 
of yellow tint though too minute to show it under the microscope Yet it is 
a curious circumstance that the same bacterium in Pasteur’s solution had not 
this colour, but produced a pale pink tint by the deposit which it formed at 
the bottom of the glass. At this period I was obliged to suspend my observa- 
tions, but from what had been seen in the last few days it appeared that the 
bacteria were converting the coagulum into a transparent liquid, for the upper 
translucent layer was daily increasing in thickness. On looking at this time 
at the second milk-glass, in which the viscous fermentation had occurred at an 
earlier period, I found that the viscid upper part had changed to a similar golden- 
yellow colour, and under the microscope I found that Bactertum No. I had 
disappeared, and given place to Bacterium No. II. This yellow colour in milk 
I never saw caused by any other organism. 
‘The last observations which I have now to relate refer to the commonest 
FO Clit. 5b 136. 
Y 32 
