THE GEXESIS OF LIFE. 167 



This observation bore a clear relation to the production of 

 life in an infusion of decaying animal matter ; since it was 

 urged, if fermentation can be shown to depend on micro- 

 scopic plant-growth, why should not the processes of ordinary 

 putrefaction and decomposition be regarded as of like origin 

 and nature ? And the researches of the late Master of the 

 Mint in England, and of various Continental observers, 

 demonstrated in time the reasonable nature of the latter 

 idea. A fluid capable of undergoing putrefaction was com- 

 pletely separated, in Graham's experiments, into two por- 

 tions by a soft bladder or membrane, through which the 

 fluid could strain, but which would present an obstacle to 

 the passage of solid bodies, however minute the latter might 

 be. Decomposing matter added to the fluid on one side 

 of the membrane produced putrefaction and an abundant 

 development of animalcular life. But whilst the decom- 

 posing fluid strained through the membrane to mingle with 

 the pure fluid on the other side, the latter fluid exhibited 

 none of the phenomena of decomposition, and remained 

 perfectly clear and free from all traces of life-development. 

 Thus, once again, but in a more exact fashion than that in 

 which Spallanzani had demonstrated the fact, were scientists 

 led to conclude that the solid and material germs or particles 

 of one kind or another, kept back by the membrane from 

 entering the pure fluid, were the cause of the putrefying 

 action in the companion fluid. A similar result and con- 

 clusion to that obtained and arrived at by Spallanzani, had in 

 short been attained through investigation which had proceeded 

 along a different and more complicated line of research. 



The demonstration of the "material" nature of the 

 infecting germs or particles was advanced a stage further 

 when Schroeder and Dutsch, experimenting between the 

 years 1854 and 1859, showed that a very effective mechanical 

 filter might be formed of simple cotton-wool; putrescible 

 fluids, contained in flasks the mouths of which were stopped 

 with closely packed wool, remaining perfectly clear and 

 barren of life. And Tyndall, taking up the line of research 



