56 
PROFESSOR TYNDALL ON THE OPTICAL DEPORTMENT OP THE 
the flush of the true opal so closely as this infusion. Filtration through 100 layers of 
paper was quite incompetent to remove the suspended particles to which this opalescence 
is due. Some of the other infusions remained turbid under filtration, without exhibiting 
what I should call opalescence. The sheep’s lungs furnish an example of this. In some 
cases, moreover, where repeated filtering failed to remove the suspended particles, a few 
weeks’ quiet caused them to sink, and leave the supernatant liquid clear. It may be 
worth remarking that some rabbit-infusions have shown a decided opalescence, while 
others have been perfectly clear. The same remark applies to turnip-infusions, some of 
which have been found as clear as distilled water, while in general a slight opalescence 
is not to be got rid of by filtering. 
These later experiments are quite in harmony with the earlier ones. Not one of this 
cloud of witnesses testifies in favour of Dr. Bastian. Not a single flask of the multitude 
manifests the deportment alleged by him to be a matter of common observation. If 
the power of spontaneous generation be a scientific verity, surely amid opportunities so 
multiplied and various it must have asserted itself. That the infusions employed were 
not “ degraded ” by the boiling so as to be incapable of supporting life, was proved by 
the fact that exposed tubes containing the same infusions, treated in precisely the same 
way, resolved themselves with the usual speed into Bacterial swarms. The conclusion 
to which these results point is, that here, as elsewhere, Dr. Bastian has allowed the 
gravest errors to invade his experimental work. 
§ 23. Conditions as to the Temperature and Strength of Infusions. 
In connexion with these experiments, I have sought, to the best of my ability, to meet 
every condition and requirement laid down by others as essential to success. With regard 
to warmth, a temperature of 90° was generally attainable in our laboratory, while 
on certain days of mild weather without, and in favourable positions within, the tem- 
perature to which the infusions were subjected reached over 100° Fahr. As Dr. Bastian, 
however, has recently laid considerable stress on warmth, though most of his results 
were obtained with temperatures from 15° to 30° lower than mine*, I thought it desirable 
to meet this new requirement also. The sealed tubes, which had proved barren in the 
Boyal Institution, were suspended in boxes copiously perforated, so as to permit of the 
free circulation of warm air, and placed under the supervision of an intelligent assistant 
in the Turkish Bath in Jermyn Street. The washing-room of the establishment was 
found to be particularly suitable for our purpose; and here, accordingly, the boxes 
were suspended. From two to six days are allowed by Dr. Bastian for the generation 
of organisms in hermetically sealed tubes. Mine remained in the washing-room for 
nine days. Thermometers placed in the boxes, and read otf twice or three times a day, 
showed the temperature to vary from a minimum of 101° to a maximum of 112° Fahr. 
At the end of nine days the infusions were as clear as at the beginning. 
* Proc. Roy. Soc. vol. xxi. p. 130. Also ‘ Beginnings of Life,’ vol. i. p. 354. 
