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organisms whatever existed in any of the tubes containing 
the boiled liquid. Single tubes of both batches were examined 
from time to time until March, 1871, the results being always 
the same. Hence it was concluded that thoroughly boiled 
liquids, preserved in tubes first prepared and sealed, remain 
perfectly free from organic forms. 
VII.—October 5.—Four tubes, each a quarter of an inch 
in diameter, were prepared in the usual manner and filled 
with Pasteur’s solution which had not been boiled. Tube 
a was placed vertically in a cork support, its end being 
truncated so as to expose the upper surface of the liquid to 
the air. Tube 6 was also placed upright, its upper end 
having been previously drawn out to a long capillary beak, 
the tip of which was broken off, so that the interior of the 
tube communicated with the atmosphere by a small aperture. 
Tube c, of the same form as 4, was also placed vertically, but 
its open point was bent downwards at a very acute angle. 
Tube d was sealed at both ends. ' 
Four similar tubes marked respectively a’, 0’, c’, d’, were 
then filled with boiling solution and placed side by side with 
the others, three of them having openings of the characters 
already described, the other being closed. On October 12 
the only change which could be distinguished without the 
microscope was a very remarkable one. A tuft of penicillium 
had appeared on the surface of the liquid in tube 0’, the 
interior of which communicated with the air only by a capil- 
lary aperture. Nothing was visible in the others; but a few 
days later it was observed that all the open tubes (a, 6, a’, 0’), 
excepting those of which the ends had been bent down, had 
similar tufts. In the course of the following six weeks the 
tufts increased considerably in size. On the 24th of November 
the liquid in tubes ¢ and d, in which no penicillium existed, 
was observed to be hazy and hada slight scum on the surface. 
Tubes ¢’ and d’ remained perfectly unaltered. The liquid in 
the open tubes was examined microscopically from time to 
time during the period of observation, the drop required for 
this purpose being on each occasion transferred to the object 
glass of the microscope either by means of a glass rod, the end 
of which had been first passed through the flame of a Bunsen’s 
burner, or the capillary tube which had been drawn out immedi- 
ately before, so as to avoid all risk of contaminating the liquid. 
In all of the open tubes containing unboiled solution torula 
cells and microzymes began to appear after the first week. — 
On November 24 they existed in great numbers, in addition 
to mycelium and filaments and spores of sporotrichum. In 
the closed tube d there were bacteria but no torula or peni- 
