Dry-rot; Venoms; Viruses 843 



soluble ferments, the diastases, resist it perfectly and are even 

 preserved by it. 



We possess then a valuable instrument of differentiation to dis- 

 tinguish what belongs to one or the other of the two classes of 

 fermentations. 



If we are dealing with a true fermentation, it will be checked 

 completely by compressed oxygen, under a tension corresponding 

 to about 30 atmospheres of air, and since the ferment is killed, it 

 will not appear again, even when the pressure becomes normal 

 once more. If the fermentation is due to the presence of a sub- 

 stance analogous to diastase, this substance, when subjected to 

 compressed air, should keep its active properties there almost in- 

 definitely, as a subsequent experiment will show. 



I make haste to say, however, that although it is very easy to 

 decide in this way whether a given phenomenon is a true fermenta- 

 tion, the method will not distinguish between a pseudo-fermenta- 

 tion and the result of a simple oxidation. An example taken from 

 the dry rot of fruit will explain my idea. 



1. Dry Rot of Fruit. 



Certain fruits, for example medlars and service-apples, are com- 

 monly attacked by dry rot, so that, since they can be eaten only in 

 this condition, it is generally confused with ripeness. Is dry rot 

 the final stage in a vital evolution of the cells of the fruit? Is it 

 the result of the reaction of a diastatic matter previously formed 

 on the tannin, which disappears during the dry rot? Or, finally, 

 the result of an oxidation of this tannin, the disappearance of 

 which takes from the fruit its disagreeable taste? Let us see first 

 what experiments say. 



Experiment CCCCLXXXIII. September 29. Service-apples not 

 affected by dry rot, in good condition, placed carefully in test glasses. 



A, left in open air. 



B, subjected to a pressure of 10 superoxygenated atmospheres. 

 October 4. Decompressed. 



A, beginning to rot. 



B, evidently still more rotten. 



Experiment CCCCLXXXIV. November 5. Medlars not affected by 

 dry rot. 



A, at normal pressure. 



B, at 17 atmospheres in air containing 78% of oxygen. 

 November 11. Decompressed. 



A, still very hard, do not suffer dry rot until a week after. 



B, completely rotten, and consequently, from the sudden decom- 

 pression and the escape of gases, cracked and burst. 



