SPONTANEOUS GENERATION. 333 



Were it not for some specific relation between the mat- 

 ter 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 re- 

 lation of the germ to its encompassing liquid. Any- 

 thing that hinders this interchange retards the destruc- 

 tion of the germ in boiling water. In my paper pub- 

 lished in the ' Philosophical Transactions ' for 1877, I 

 add the following remark: 



It is not difficult 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 produce the swelling and softening which precede its 

 destruction in a liquid of high temperature. 



However this may be whatever be the state of the 

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

 they do as a matter of certainty resist, under some cir- 

 cumstances, 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, if not thousands, of rigidly conducted ex- 

 periments. 



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-enquirer two liquids which 

 have been kept for six months in one of our sealed 



