DR. W. ROBERTS ON BIOGENESIS. 
467 
The next step was to destroy any germs adhering to the interior of the bulbs and 
tubes or floating in the air within them — in other words, to sterilize them. This was 
done in the case of the bulbs by introducing water into them before the plugging, 
and boiling over the flame for ten minutes. The tubes were sterilized by passing and 
repassing them through the flame yf the spirit-lamp until they were quite hot, as shown 
by commencing charring of the cotton-wool plug. If the conditions of the experiment 
required that there should be some water in the tubes, their capillary ends were snipped 
off (after sterilization) and boiling water was sucked into them, and the ends again 
resealed. Bulbs and tubes thus prepared might be regarded as “ sterilized chambers ” 
— that is to say, chambers deprived of germinal particles by the destructive power of 
heat, and having free access of air, also deprived of germs by filtration through the 
cotton-wool plug. A number of such sterilized bulbs and 
tubes (some containing water and some empty) were pre- 
pared and laid aside for future use. 
Experiments were made on the following substances : — 
1. Egg-albumen . — Two sets of experiments were made 
with egg-albumen. 
First set. — At the end of March, 1873, eight sterilized 
bulbs (fig. 3, A) containing water were charged with egg- 
albumen, in the following manner : — 
A fresh egg was fixed in a convenient support, and a 
small piece of the shell was chipped off, care being taken 
to leave the subjacent membrane uninjured. Then a steri- 
lized bulb was taken and the capillary portion (b e) im- 
mersed for a few seconds in boiling water in order to 
destroy any adhering germs. The sealed end was then 
rapidly snipped off, and the capillary portion plunged into 
the interior of the egg. About two cubic centimetres of 
the albumen were then sucked up by the mouth into the 
bulb. When this was accomplished, the bulb was quickly 
withdrawn, and its capillary end sealed in the flame. 
At first the albumen formed a distinct layer below the 
water in the bulbs ; but in a few days the soluble portions diffused into the water 
above, and formed a transparent colourless solution, while the scanty insoluble por- 
tions separated in a hazy cloud or flakes which occupied the lower strata of the fluid. 
These eight bulbs were kept through the ensuing summer and autumn, and were 
finally examined on the 1st of October. Six of them were quite unaltered in appearance, 
and no trace of any organism could be detected under the microscope. The other 
two were evidently changed. They had become turbid a few days after being put up? 
and had become increasingly so for a few weeks, after which they underwent no further 
3 Q 2 
Eig. 3. 
I 
U* n 
A. Sterilized bulb. B. Sterilized 
tube. About half the actual 
dimensions. 
