168 LEISURE-TIME STUDIES. 



at the point where Schroeder and Dutsch had ceased their 

 experimentation, demonstrated that, as far as the atmosphere 

 itself is concerned, it may be described as a " stirabout " of 

 minute particles. These particles are of varying nature ; 

 some are living, others inorganic; they are disguised and 

 unperceived in diffuse daylight, it is true, but are revealed 

 by the brilliant lights at the command of science, or, in 

 more homely fashion, by the sunbeam streaming through the 

 chink of a shutter into a darkened room. Nor may the 

 name of Pasteur, the distinguished French chemist and 

 physicist, be omitted from the list of experimenters on the 

 causes and origin of life developed in fluids. It was left for 

 Pasteur to supply the missing link in the evidence regarding 

 the nature of those particles contained in fluids or borne by 

 the atmosphere, which research, from the days of Spallanzani 

 and onwards, had disclosed. Microscopic examination of 

 the cotton-wool used to plug the mouths of flasks, as 

 described in the experiments of Schroeder, revealed to 

 Pasteur the presence of numerous small particles which the 

 wool had filtered off from the air passing into the infusion. 

 These particles, on being sown in fitting solutions and duly 

 watched thereafter under the microscope, were seen to 

 develop into adult forms of animalcules and of lower plants. 

 The identity of the atmospheric particles with the germs of 

 animalcular life was thus fully proved ; and the innate truth 

 of the "germ theory" maybe regarded as having in this 

 manner been demonstrated. 



The first proposition which at this stage of our inquiries 

 may therefore be submitted, is that the germ theory, which 

 holds that lower forms of life, developed in infusions of 

 organic matter, proceed from the germs originally contained 

 in the fluid, or which have gained access thereto from the 

 atmosphere, may be regarded as fully proved. As we shall 

 presently note, it matters not, so far as the truth of this 

 proposition is concerned, if " spontaneous generation " also 

 be ultimately proved to occur. The actual demonstration 

 of the fact that some forms of life could be produced de novo. 



