468 
DE. W. EOBEETS ON BIOGENESIS. 
change. Under the microscope spherical Bacteria were seen abundantly, and a few 
cells resembling Torulce. There were, however, no staff-shaped Bacteria and none of 
the usual signs of putrefaction. 
Second set. — On the 17th of December, 1873, seven sterilized tubes containing water 
(fig. 3, B) were charged with egg-albumen in the manner above described. Of these, 
two became turbid with Bacteria ; the other five continued transparent, and when 
examined at the end of two months were found quite free from organisms. 
2. Blood. — The end of the finger was thoroughly cleansed, and blood drawn therefrom 
by needle-punctures. The blood was sucked into sterilized tubes containing water, 
and then sealed in the flame with the precautions above described. About two drops of 
blood were conveyed into each tube. In these experiments there was obviously consi- 
derable risk both of air- and of water-contamination. Ten tubes were put up in this way, 
and examined at the end of four weeks. Four of them had assumed a bright red colour 
and deposited a sediment, and were more alkaline than the others. These were found to 
contain Bacteria. The other six had an amber tint and no sediment ; these were quite 
free from organisms. 
3. Urine. — Fresh urine was received into a large superheated test-tube. Six steri- 
lized tubes, not containing any water, were charged with the urine in the usual way, 
and then sealed at their capillary ends. The urine was alkaline and turbid from preci- 
pitated phosphates. On the following day two more tubes were similarly charged with 
acid urine. Of these eight tubes one became turbid from Bacteria , the other seven 
were found, at the end of eight weeks, perfectly unaltered and free from organisms. 
4. Blister-serum. — Four sterilized tubes, not containing any water, were charged with 
blister-serum. The broken capillary ends were thrust directly through the raised epi- 
dermis into the sac of the blister, and the serum was sucked into the tubes to the depth 
of about an inch and a half. The tubes were then quickly withdrawn, and their capillary 
ends resealed in the flame. At the end of ten weeks all four were found unaltered and 
perfectly free from organisms. 
5. Milk. — Milk is very difficult to obtain free from extraneous contamination. In 
my earlier attempts I used superheated test-tubes plugged with cotton-wool. Test- 
tubes so prepared were taken into the cowhouse at milking-time, and charged with milk 
by momentary removal and reinsertion of the plugs. Milk so obtained, however, inva- 
riably curdled in a week and swarmed with Bacteria. 
I afterwards adopted the following plan with somewhat better success : — A glass tube 
(a b, fig. 4) was drawn out at each end to a narrow orifice. The lower portion of this 
was tightly wrapped round with cotton-wool and inserted as a plug into a large test- 
tube (c) containing water to the depth of about an inch. A cap of cotton-wool was 
also tied over the narrow orifice at a. The water in the test-tube was then briskly 
boiled, and the boiling was continued almost to dryness. When the apparatus was cold 
I took it into the cowhouse and, seizing a teat, I pulled off quickly the cotton-wool cap 
