DISEASE-GERMS. 247 



decomposition, even in the presence of atmospheric air, any such 

 action being originated and maintained only by the developmental 

 action of definite organic germs. 



2. That different kinds of fermentation (using that term in its 

 large sense) are produced by organic germs of different species. Thus, 

 while torula sets going the alcoholic fermentation in a saccharine wort, 

 other fungoid germs will set up the acetous, and others, again, the pu- 

 trefactive fermentation, when introduced into fluids of the same kind. 



3. That many different kinds of germs notably those of the bac- 

 teria, which induce putrefactive fermentation are constantly floating 

 in the ordinary atmosphere, so as to be almost certainly self-sown in 

 any organic fluid freely exposed to it. 



4. That, if these germs be removed by mechanical filtration, or be 

 got rid of by subsidence, or be deprived of their potency by chemical 

 agents which destroy their vitality, the most readily decomposable 

 organic fluid may be subjected to the freest contact with the air from 

 which the germs have been thus eliminated without undergoing any 

 change. 



5. That, as there is no such thing as fermentation without the 

 presence of germ-particles, so there is no such thing as the spontaneous 

 origination of such germs, each kind, when sown in the liquid, repro- 

 ducing itself with the same regularity as in higher plants, and thus 

 continuously maintaining its own type. 



6. That such germ-particles, when dried up, can not only maintain 

 their germinal power for unlimited periods, starting into renewed 

 activity so soon as the requisite conditions are supplied, but that, in 

 this state of dormant vitality, they can be subjected to influences 

 which would destroy the life of the growing plants such as very high 

 or very low temperatures, the action of strong acid or alkaline solu- 

 tions, and the like.* 



The first application of these doctrines to the study of disease in 

 the living animal was made in a very important investigation, com- 

 mitted to Pasteur by his old master in chemistry (the eminent and 

 eloquent Dumas), into the nature of the pebrine, which was threaten- 

 ing to extinguish the whole silk-culture of France and Italy. It had 

 been previously ascertained that the bodies of the animals affected 

 with this disease (whether in the worm, chrysalis, or moth stage) 

 swarm with peculiar minute corpuscles, which even pass into the un- 

 developed eggs of the female moth, but there was no evidence that 

 these corpuscles were independent, self-developing organisms intro- 

 duced from without, many regarding their presence as a mere expres- 

 sion or concomitant of the disorder, not as its cause. It would be too 

 long to detail the steps of this most complicated and difficult inquiry, 

 and I must satisfy myself with the mere statement that it not only 



* The evidence on which these conclusions rest is fully stated in Professor Tyndall's 

 recently published treatise on the " Floating Matter of the Air." 



