306 FRAGMENTS OF SCIENCE. 



tell us they are vegetables. From the rod-like . shape 

 which they so frequently assume, these organisms are 

 called ' bacteria ' a term, be it here remarked, which 

 covers organisms of very diverse kinds. 



Has this multitudinous life been spontaneously 

 generated in these six flasks, or is it the progeny of 

 living germinal matter carried into the flasks by the 

 entering air? If the infusions have a self-generative 

 power, how are the sterility and consequent clearness of 

 the fifty-four uninjured flasks to be accounted for? 

 My colleague may urge and fairly urge that the 

 assumption of germinal matter is by no means neces- 

 sary ; that the air itself may be the one thing needed 

 to wake up the dormant infusions. We will examine 

 this point immediately. But meanwhile I would remind 

 him that I am working on the exact lines laid down 

 by our most conspicuous heterogenist. He distinctly 

 affirms that the withdrawal of the atmospheric pressure 

 above the infusion favours the production of organisms ; 

 and he accounts for their absence in tins of preserved 

 meat, fruit, and vegetables, by the hypothesis that 

 fermentation has begun in such tins, that gases have 

 been generated, the pressure of which has stifled the 

 incipient life and stopped its further development. 1 

 This is the new theory of preserved meats. Had its 

 author pierced a tin of preserved meat, fruit, or vege- 

 table under water with the view of testing its truth, he 

 would have found it erroneous. In well-preserved tins 

 he would have found, not an outrush of gas, but an 

 inrush of water. I have noticed this recently in tins 

 which have lain perfectly good for sixty- three years in 

 the Eoyal Institution. Modern tins, subjected to the 

 same test, yielded the same result. From time to time, 

 moreover, during the last two years, I have placed glass 

 1 Beginnings qf Life, vol. i. p. 418. 



