DR. W. ROBERTS ON BIOGENESIS. 
471 
The following Table exhibits a summary of the results : — 
Liquid or tissue 
experimented on. 
Number of 
experiments. 
Results. 
Remained 
sterile. 
Became 
fertile. 
Egg-albumen .... 
15 
11 
4 
Blood 
10 
6 
4 
Urine 
8 
7 
1 
Blister-serum . . 
4 
4 
0 
Milk 
10 
3 
7 
Grape-juice .... 
11 
11 
0 
Orange-juice .... 
8 
8 
0 
Tomato-juice .... 
3 
3 
0 
Turnip-tissue .... 
14 
10 
4 
Potato-tissue .... 
7 
4 
3 
Totals. 
90 
67 
23 
Thus out of 90 experiments on the juices and tissues of plants and animals, exposed 
to conditions favourable to germination, absolute sterility was observed 67 times, and 
development of organisms only 23 times. It was scarcely possible to obtain a more clear 
demonstration of the general conclusion that the normal tissues and juices have no 
inherent power to originate organisms, and that when organisms appear therein their 
development is due to germs imported from without. 
Section III.— ON THE BEARING OE THE FACTS ADDUCED IN THE PRECEDING SECTIONS ON 
THE ORIGIN OF BACTERIA AND TORULAE, AND ON THE REAL EXPLANATION OF SOME 
OF THE ALLEGED CASES OF ABIOGENESIS. 
We have seen that organic liquids and mixtures sterilized by heat, and the normal 
fluids and tissues of plants and animals, remain permanently barren, under the most 
favourable conditions of air, moisture, warmth and light, so long as they are protected 
from extraneous infection; but if unfiltered air or ordinary water be brought into 
contact with them, this barrenness is immediately and invariably succeeded by fertility. 
Such a sequence of events can only be explained by the supposition that there exist 
in ordinary air and water, in addition to their proper elements, incredible multitudes 
of particles capable of provoking germination. 
The exact nature of these germinal particles is, however, not a matter of actual 
knowledge. It is evident that they are organic, because of their easy destructibility by 
heat. It is further evident that the atmospheric germs are solid particles, for they can 
be mechanically filtered from the air, and they are incapable of ascending against 
gravity. It may be assumed that they consist partly of true spores and partly of the 
organisms themselves, floating amid the dust of the atmosphere or mingled with the 
molecular matter always present in ordinary water. But it cannot be said that they 
