PERSISTENCE OE PUTREFACTIVE AND INFECTIVE ORGANISMS. 
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soon cease to be equal in vigour. The life of the one is promoted, the life of the other 
only tolerated by its environment. When the temperature surrounding both is raised 
to a prejudicial height the one will suffer more than the other, because equally inclement 
conditions are brought to bear upon constitutions of different strengths ; and if the 
temperature be sufficiently exalted or sufficiently prolonged to become fatal, the more 
weakly organism will be the first to give way. A germ, moreover, brought close to the 
death-point in a neutral or an alkaline infusion may revive, while in an acid one it 
may perish — just as proper nutriment may rescue a dying man while improper 
nutriment would fail to do so. These elementary considerations, founded on the 
demonstrable fact that Bacteria-genas are more fully vivified and better nourished in 
neutral infusions than in acid ones, suffice, I think, to explain the observed difference 
of action. At all events, these are the thoughts which have become rooted in my mind, 
through long observation and long pondering of this question*. 
§ 21. Remarks on the Germs of Bacteria as distinguished from Bacteria themselves. 
The failure to distinguish between these stubborn germs and the soft and sensitive 
organisms which spring from them has been a fruitful source of error in writings 
on Biogenesis. In his able and important paper, “On the Origin and Distribution of 
Bacteria in Water, and the circumstances which determine their existence in the Tissues 
and Liquids of the Living Body,” Dr. Burdon Sanderson, for example, has described 
experiments from which, in my opinion, very incorrect conclusions have been drawn. 
He exposed to the common air vessels containing Pasteur’s solution, which when 
inoculated with fully developed Bacteria enables them freely and copiously to increase 
and multiply ; he even caused the air to bubble through the solution, and finding that 
though Torula and Penicillium were luxuriantly developed in the liquid, Bacteria never 
made their appearance, he concluded, “ not merely that the conditions of origin and 
growth of Bacteria and fungi are considerably different, but that, as regards the former, 
the germinal matter from which they spring does not exist in ordinary air” f. These 
italics occur in the paper from which I quote. 
Dr. Sanderson subsequently reaffirms the position here laid down. “ In my preceding 
experiments,” he says, “ it has been shown that although Torula- cells and Penicillium 
appear invariably, and without exception, on all nutritive liquids of which the surfaces 
are exposed to the air, without reference to their mode of preparation, no amount of 
exposure has any effect in determining the evolution of Bacteria”%. And, again, with 
reference to another experiment: — “The result shows that ordinary air is entirely free 
* From their deportment in boiling, I should infer that the air dissolved in an alkaline liquid is in a different 
physical condition from that dissolved in an acid liquid ; and to this, in some measure, the difference of nutritive 
power may he due. I have been unable to find any experiments on the comparative absorption of air by acid 
and neutral liquids. The subject is, I think, well deserving of attention. 
+ Appendix to the Thirteenth Report to the Medical Officer of the Privy Council for 1871, p. 335. 
t ‘ Appendix,’ p. 338. Though Dr. Sanderson speaks of “ all nutritive liquids,” if I understand him 
aright, he really tried but one, and that was a mineral solution, not an animal or vegetable infusion. 
MDCCCLXXVII. 2 E 
