392 Address of Professor Hualey. 
strated that ordinary air is no better than a sort of stir-about of 
excessively minute solid particles ; that these particles are almost 
wholly destructible by heat ; and that they are strained off, and 
me air rendered optically pure by being passed through cotton- 
ool. 
Ta it remains yet in the order of logic, though not of his- 
tory, to show that among these solid destructible particles there 
really do exist germs capable of giving rise to the development 
of living forms in suitable menstrua. This piece of work was 
done by M. Pasteur, in those beautiful researches which will 
ever render his name famous; and which, in spite of all attacks 
upon them, appear to me now, as they did seven years ago,* to 
be models of accurate experimentation and logical reasoning. 
He aaa air through cotton-wool, and found, as Schroeder 
and Dusch had done, that it contained nothing competent to 
give rise to the development of life in fluids highly fitted for 
ae that purpose. But the important further links in the chain of 
_, evidence added by Pasteur are three. In the first place he sub- 
_ jected to microscopic examination the cotton-wool which had 
we served as strainer, and found that sundry bodies clearly recog- 
_ nizable as germs, were among the solid. particles strained off 
es “Secondly, he proved that these germs were competent to give 
‘rise to living forms by simply sowing them in a solution fitted 
| for their development. And, thirdly, he showed that the in- 
| capacity of air strained through cotton-wool to give rise to life, 
was not due to any occult b ohange effected in constituents of the 
air by the wool, by proving that the cotton-wool might be dis- 
pensed with altogether, Bet: perfectly free access left between 
the exterior air and that in the experimental flask. If the neck 
of the flask is drawn out into a tube and bent downward; and 
if, after the contained fluid has been carefully boiled, the tube 
is heated sufficiently to destroy any germs which may ‘be pa 
in the air which enters as the fluid cools, the apparatus ma 
left to itself for any time, and no life will appear in the fluid. 
The reason is plain. Alt though t there is free communication be- 
tween the winvoapbare laden with germs and the germless air in 
the flask, contact between the two takes dlace only in the tube ; 
and as the germs cannot fall upward, and there are no curren’ 
Boge! never reach the interior of the took But if me tube be 
te short off where it proceeds from the flask, ac- 
cess be thus given to germs falling vertically out of ae air, the 
fluid which has remained clear and desert for months, becomes, 
ina pe days turbid and full of life. 
<aica Salegp riments have been repeated over and over again 
Ee indepe ent observers with entire success; and there is one 
BEE fy conaiag to Working Men on the Causes of the Phenomena of Onanie es 
sail ic ich ele. 
