310 THE FLOATING-MATTEE OF THE AIR. 



Were it not for some specific relation between the 

 matter of the germ and that of the liquid into which 

 it falls, wetting would be simply impossible. Antece- 

 dent to all development there must be an interchange 

 of matter between the germ and its environment ; 

 and this interchange must obviously depend upon the 

 relation of the germ to its encompassing liquid. Any- 

 thing that hinders this interchange retards the de- 

 struction of the germ in boiling water. In my paper, 

 published in the ' Philosophical Transactions' for 1877, 

 I add the following remark : — 



It is not difBcult to see that the surface of a seed or germ 

 may be so affected by desiccation and other causes as practi- 

 cally to prevent contact between it and the surrounding 

 liquid. The body of a germ, moreover, may be so indurated 

 by time and dryness as to resist powerfully the insinuation 

 of water between its constituent molecules. It would be 

 difficult to cause such a germ to imbibe the moisture neces- 

 sary to pi'oduce the swelling and softening which precede its 

 destruction in a liquid of high tempei-ature. 



However this may be — whatever be the state of the 

 surface, or of the body, of the spores of Bacillus subtilisy 

 they do as a matter of certainty resist, under some 

 circumstances, exposure for hours to the heat of boiling 

 water. No theoretic scepticism can successfully stand 

 in the way of this fact, established as it has been by 

 hundreds — nay thousands, of rigidly conducted expe- 

 riments. 



We have now to test one of the principal founda- 

 tions of the doctrine of spontaneous generation as 

 formulated in this country. With this view, I place 

 before my friend and co-inquirer two liquids which 

 have been kept for six months in one of our sealed 

 chambers, exposed to optically pure air. The one is a 



