102 Pasteur's Researches on Putrefaction. 



becomes so intense that the microscopic examination of a single 

 drop is very unpleasant. The fetid odour depends chiefly on 

 the proportion of sulphur the substance contains. The odour 

 is scarcely sensible if the matter is not sulphuretted, as, for 

 example, in the fermentation of the albumenoid matter which 

 water can carry away from the yeast of beer. The same is 

 the case with butyric fermentation ; and after my experiments 

 butyric fermentation must, from the nature of its ferment, be 

 considered as a phenomenon of exactly the same order as pu- 

 trefaction properly so called. Thus we see what happens when 

 putrefaction is in some sort restrained." 



" It results from what precedes, that contact with air is not 

 necessary to the development of putrefaction, but that, on the 

 contrary, if the oxygen, dissolved in a putrescible liquid, is not 

 removed by the action of special beings, putrefaction will not 

 occur, as the oxygen would cause the vibrions to perish if they 

 tried to develope themselves." 



" I shall now examine the case of free putrefaction in con- 

 tact with air. That which I have already said might make it 

 appear that it could not take place under such circumstances, 

 as oxygen kills the vibrions which excite it. Notwithstand- 

 ing this, I shall demonstrate that putrefaction in contact with 

 air is more complete than when it is effected under shelter 

 from air." 



" Let us go back to our aerated liquid, this time exposed 

 to contact with air in a wide-mouthed vessel. The removal of 

 the oxygen takes place as previously described. The difference 

 is that the bacteriums, etc., do not perish, but propagate them- 

 selves to infinitude at the surface of the liquid which is in con- 

 tact with the air. They form a thin pellicle, which gradually 

 thickens, falls into rags to the bottom of the vessel, is formed 

 again, and so forth. This pellicle, with which is usually asso- 

 ciated divers mucors and mucedines, prevents the solution of 

 oxygen gas in the liquid, and thus permits the development of 

 the vibrio-ferments. Jb'or them the vessel is as if closed against 

 the introduction of air. They can even multiply in the pellicle 

 at the surface, because they find themselves protected by the 

 bacteriums and mucors against too direct an action of the atmos- 

 pheric, air." 



"The putrescible liquid thus becomes the seat of two kinds 

 of action, very distinct, and which are in relation to the physio- 

 Logical functions of the fcwp kinds of beings that nourish thein- 

 in it. The vibrions, on one hand, living without the aid 

 of atmospheric oxygen, determine, in the interior of tho liquid, 

 acts of fermentation — that is to say, they trans form nitrogenous 

 substances into more; simple, though still complex, products. 

 The bacteriums or the mucors burn these same products, and 



