466 
DE. W. EOBEETS ON BIOGENESIS. 
due to the agency of imported germs, and not to any act of so-called spontaneous 
generation. 
The importance of this path of inquiry was distinctly indicated by Pasteur ; but he 
does not appear to have pursued it, except in regard to urine, which he succeeded 
in keeping unaltered without heating*. 
More recently Dr. Burdon Sanderson'!’, i* 1 admirable studies on contagion, inci- 
dentally encountered this question, and arrived at some very remarkable results. He 
satisfied himself that blood, muscle, urine, saliva, milk, egg-albumen, healthy pus, and 
blister-sejum had no power of breeding Bacteria except when infected with ordinary 
water. Mr. Lister tested this question more directly, and succeeded in showing that 
blood, milk, and urine remained permanently barren when preserved from the contact 
of extraneous germs. 
Dr. Sanderson’s experiments were planned on the supposition entertained by him 
that Bacteria-ge rms, while abundant in water, were almost absent from the air. In 
repeating some of his experiments, I failed in obtaining similar results. The air of the 
rooms wherein I worked was evidently highly charged with Bacteria-germs. In pur- 
suing the inquiry, therefore, I sought to avoid air-contamination as sedulously as water- 
contamination $. 
The experiments which follow were all carried Out on a plan which was, in principle, 
the same in every case. The materials of the experiment were enclosed in sterilized glass 
bulbs or tubes, which were plugged at one end with cotton-wool and hermetically sealed at 
the other. They were then set aside in a warm place to see if they would germinate. 
The bulbs and tubes were prepared in the following manner : — They were first drawn 
out at the lower ends into capillary points (fig. 3, b, h) and sealed in the flame; the 
upper ends were plugged at a , a with cotton-wool. 
* Annales de Chimie et de Physique, 1862, p. 66.’ 
f Thirteenth Eeport of the Medical Officer of the Privy Council, p. 65. 
X The avoidance of air-contamination is important for another reason. The air is admitted, hy most 
observers, to he highly charged with fungoid germs, and the growth of fungi has appeared to me to be anta- 
gonistic to that of Bacteria, and vice versa. I have repeatedly observed that liquids in which the Penicilivm 
glaucum was growing luxuriantly could with difficulty he artificially infected with Bacteria ; it seemed, in fact, 
as if this fungus played the part of the plants in an aquarium, and held in check the growth of Bacteria, with 
their attendant putrefactive changes. On the other hand, the Penicilium glaucum seldom grows vigorously, if 
it grow at all, in liquids which are full of Bacteria. 
It has further seemed to me that there was an antagonism between the growth of certain races of Bacteria 
and certain other races of Bacteria. 
On the panspermic theory it may he assumed that what takes place when an organic liquid is exposed to the 
contamination of air or water is this : — A considerable variety of germinal partieles are introduced into it, and 
it depends on a number of conditions (composition of the liquid, its reaction, precedence and abundance of the 
several germs) which of these shall grow and take a lead, and which shall partially or wholly lie dormant and 
unproductive. There is probably in such a case a struggle for existence and a survival of the fittest. And it 
would he hazardous to conclude because a particular organism was not found growing in a fertile infusion, that 
the germs of that organism were really absent from the contaminating media. 
