190 
PROFESSOR TYNDALL ON THE DEPORTMENT AND VITAL 
from living Bacteria'*. His general conclusion is that, as regards the development of 
Bacteria in organic liquids, “ water is the contaminating agent.” 
Upon these experiments, and the conclusion drawn from them, an argument has been 
founded by Dr. BASTiANf, which would be weighty were its basis sure. In reference 
to the Presidential Address of the British Association in Liverpool $, he argues 
thus : — “ Speaking of living Bacteria germs, Professor Huxley summed up by saying, 
‘ considering their lightness, and the wide diffusion of the organisms which produce them, 
it is impossible to conceive that they should not be suspended in the atmosphere in 
myriads.’ Had Profesor Huxley himself made some careful and discriminating experi- 
ments on this part of the subject, he might have found that the supposed impossibility 
of conception was entirely delusive What has been the subsequent progress of 
events % In the first place, it has been shown by Professor Burdon Sanderson, myself, 
and others, that the living Bacteria germs are not diffused through the air to any appre- 
ciable extent ; and this is now a very widely accepted doctrine, in spite of its being, as 
Professor Huxley imagined, an impossible conception.” The “ others ” referred to by 
Dr. Bastian embrace among them, it is to be admitted, the celebrated naturalist Cohn. 
Dr. Bastian was quite correct in saying that the “ doctrine ” he enunciated was, at that 
time, “ widely accepted.” It is, nevertheless, one of those cases in which the general 
acceptance of a doctrine fails to establish its truth. It is, indeed, an entirely erroneous 
doctrine, founded, I will not say upon incorrect experiments, but on the misinterpretation 
of incomplete ones. I have already referred to this error, and should not do so now had 
it not been lately revived. The deportment of almost any sterilized animal or vegetable 
infusion exposed to common air will disprove the doctrine. It has been disproved 
repeatedly by experiments with melon-, turnip-, cucumber-, and hay-infusions, alluded 
to in this memoir. Such infusions, after having been sterilized by exposure for six or 
eight hours to the boiling-temperature, remain, if protected from the Bacteria-ge rms 
of the air, for ever barren ; but when infected spontaneously, or purposely, by atmo- 
spheric germs, they are found, within eight and forty hours after such infection, thickly 
crowded with Bacteria. That London air is laden with living Bacteria germs is as 
certain as that London chimneys are laden with smoke. What Dr. Sanderson’s important 
experiments really prove is, that a mineral solution competent to nourish the Bacteria after 
they have been fully developed is not competent (or, rather, but very feebly competent) 
to effect the transfer from the germ state to that of the finished organism. It can feed 
the chick, but it cannot hatch the egg. As I have already expressed it, the experiment 
proves, not the absence of Bacteria-ge rms from the air, but the inability of the mineral 
solution to develop them. 
Another experiment, described by Dr. Sanderson in the paper above referred to, is 
this : — “ A glass rod was charged with Bacteria by dipping it into a solution on the 
surface of which there was a viscous scum, consisting entirely of these bodies imbedded 
in a gelatinous matrix. The rod was allowed to dry in the air for a few days. It was 
* ‘ Appendix,’ p. 339. + ‘ Evolution,’ p. 44. J Brit. Assoc. Report, 1870. 
