A CONTRIBUTION TO THE BIOLOGY OF BACTERIA. 191 
I refer to the original for an account of the details of the 
experiment. 
The result was invariably that the urine in the control experi- 
ments remains clear and apparently unaltered for an indefinite 
time; whilst where the potash had been allowed to act upon the 
sterilised fluid it became turbid, lighter in colour, and swarmed 
with organisms in from eighteen to twenty-six hours, on the 
average. 
In repeating these experiments I have closely followed Dr. Bas- 
tian’s directions, with the exception that the potash tubes were made 
by drawing out test tubes in the middle, charging them with the 
requisite amount of liquor potassae, and then hermetically sealing 
them by melting, and thus separating the upper part of the 
tube. This procedure is much more convenient than the original 
method; and the sterilisation called for is ensured fully by 
keeping such tubes in boiling water during twenty minutes, as, 
says Dr. Bastian, in these experiments I soon found that the 
longer or shorter duration of the period of boiling of the liquor 
potassae tubes did not appreciably influence the results. 
Dr. AV. Koberts and M. Pasteur could not obtain the same 
results, and it is furthermore not absolutely certain that all germs 
were kept out of the retorts when Dr. Bastian boiled the tubes 
in oil during a period of twenty hours. He himself mentions the 
difficulty of properl}" cleaning them then and, even if it be con- 
ceded that those contained within the tubes were destroyed, 
fresh germs might possibly adhere to the exterior, whereas the 
heat and the period of immersion of the urine retort in boiling 
water would be the only safeguard against a contamination with 
such germs. 
If the views of all experimenters in regard to the degree of 
heat and the duration of its action are compared, it may be 
allowed to doubt that the germs in the vessels are all destroyed. 
It appears that micrococci and the so-called spores of Bacillut 
suhtilis and Bacillus anthracis retain their vitality in consider- 
ably higher temperatures than do the fully developed Bacillus 
and shorter rod-forms. 
It is true that the concentration of the fluid is changed if 
heated longer than to ebullition before sealing, and therefore one 
may entertain doubts of complete sterilisation so long as Dr. 
Bastian cannot either eliminate this possibility or disregard the 
change. One is strongly reminded of Needham^s objections to 
Spallanzani^s experiments in the last century, when Dr. Bastian 
says that if Pasteups modification to continue the boiling were 
introduced, the urine might undergo a chemical change. But 
not alone is the uncertainty of a thorough sterilisation of great 
weight in the a priori estimation of the final success of such 
