470 
DR. W. ROBERTS ON BIOGENESIS. 
juice of half-ripe tomatoes. The proceeding followed was the same as with oranges. 
At the end of two months the supernatant liquor in the tubes was perfectly trans- 
parent, and no appearance of organisms was found under the microscope. 
9. Turnip . — I found it much less easy to deal with the solid tissue of the turnip and 
potato than with the liquid pulp of the grape and orange ; 
but the results obtained, though less uniform, were not less 
conclusive. The following was the plan adopted : — A 
sterilized tube (fig. 5, A) containing water was nicked with 
a file near the base of the capillary part at a , where the 
tube had a diameter of about two millimetres. A fresh 
oblong turnip was then fractured across, and the tube, 
snapped off at the nicked point, was quickly thrust into 
the substance of the turnip. A narrow cylinder of turnip- 
tissue, about an inch long, was thus forced into the column 
of water in the tube. The tube was then detached, and 
its end sealed with melted sealing-wax (fig. 5, B). 
Fourteen tubes were charged in this way, and examined 
from time to time in the course of the ensuing two months. 
Ten remained sterile and four became fertile. The water 
in the former continued perfectly limpid, and no organisms 
could be discovered in it when examined microscopically. 
The water in the latter became turbid, and was found to 
swarm with Bacteria. 
10. Potato . — Seven sterilized tubes, containing water, were charged with potato- 
tissue in the way above described for turnip. Of these, four remained barren, and 
three became fertile with Bacteria. 
Conclusions . — As already stated, the ideal conditions of the experiments could not in 
any case be carried out with absolute stringency. Some risk of extraneous infection 
was always encountered in conveying the materials of the experiments into the steri- 
lized bulbs and tubes. The results obtained are therefore not altogether uniform ; but 
as this was in accordance with the expectation of the experiments, it adds to, rather 
than detracts from, their validity. Where the conditions of the experiments could be 
carried out in almost ideal perfection, as with egg-albumen, urine, blister-serum, grape- 
and orange-juice, the results were nearly uniform ; but when, on the contrary, the risk 
of extraneous infection was obviously considerable, as with blood, milk, turnip, and 
potato, the results were less uniform, though even in these cases, with the single excep- 
tion of milk, the sterile tubes were in a majority. 
Eig. 5. 
