17 



Is it, then, a solid ? If so we must suppose that there are 

 exactly the same number of particles of ferment as there are of 

 Bacteria, and not only so, but each Bacterium must be accom- 

 panied by its own special portion. This experiment brings 

 fermentation home to the Bacteria as nearly as can be. But it has 

 been objected that it is not possible to introduce into a liquid a 

 chemically clear organism, and until you can do so the absolute 

 proof cannot be estabhshed. The results of these investigations 

 may be thus summarised : — 



(1). Organic substances show no inherent tendency to decom- 

 position, even when exposed to the action of air or water 

 previously purified. 



(2). Organic substances exposed to impure air or water, 

 under suitable conditions of warmth and moisture, undergo fer- 

 mentation or decomposition. 



(3). This fermentation is associated with the presence of 

 certain organisms. 



(4). There is very strong evidence, although perhaps not 

 absolute proof, that these organisms are the cause of the fermen- 

 tation, and probably there are special organisms, each associated 

 with a special process. 



These discoveries have already borne abundant fruit, not 

 only in the improved methods of preserving articles of food in a 

 condition more or less allied to freshness, but also in rendering 

 possible a scientific study of antiseptics and disinfectants. 



Thus far I have dealt with these micro-organisms, in their 

 relation only to dead organic matter. When I fixed upon this 

 subject for my address, my intention was to lay before you, as far 

 as I could, what is known of their relation to certain important 

 and very fatal diseases; but, as I said at first, I felt that I should 

 not make myself understood unless I commenced my subject from 

 ihe beginning. I regret to find that my time is now exhausted, 

 and that I must defer to another occasion the second, and perhaps 

 the more important part of my subject. 



Under the microscopes on the table will be seen specimens of 

 some of the organisms to which I have referred. 



