98 The Science of Life. 



He opened twenty sealed flasks containing organic in- 

 fusions in the pure air of the Mer de Glace, and only 

 one thereafter showed signs of life; but eight out of 

 twenty opened on the plains, and all of the twenty 

 opened in town, developed germs. By these and other 

 experiments, which are commonplace already e.g. find- 

 ing the germs which were caught in the cotton wool 

 filters, and proving that they developed when placed in 

 suitable solutions he was led to his brusque conclusion 

 that "spontaneous generation is a chimera", which, as 

 a statement of fact, is true. 



Although the great achievements of Tyndall (1820- 

 93) were in physical, not biological research, his work 

 T ndaii m connec ^ on with spontaneous generation 

 must always have honourable mention. As 

 early as 1869 he had made ingenious experiments in 

 regard to the particles which float in the air, and for 

 some years afterwards he continued to apply the exact 

 methods of experimental physics to the question, "Can 

 air, retaining all its gaseous mixtures, but cleaned from 

 mechanically suspended matter, produce putrefaction?" 

 The result was to show that when dust was present, 

 rotting occurred in the exposed infusions; when dust 

 was absent, there was no rotting. 



In the course of his experiments Tyndall made the 

 important discovery, which has been recognized by all 

 bacteriologists, that to secure absolute sterility in infu- 

 sions it is safer to have an intermittent application of 

 heat. In other words, what a single boiling may not 

 ensure, since the spores of some bacteria are much more 

 resistant than the full-grown cells, is certainly effected 

 by subjection to high temperature on three consecutive 

 days. 



In concluding his experiments, Tyndall said, with 

 justifiable confidence: "There seems no flaw in this 

 reasoning; and it is so simple as to render it unlikely 

 that the notion of bacterial life developed from dead dust 

 can ever again gain currency among the members of a 

 great scientific profession ". 



In his presidential address to the British Association 

 in 1870 Huxley declared his conviction that the fact of 



