310 M. Dutrochet on the Origin of Mouldiness. 



microscopic globules, and which appear to me to be a vegetable 

 infusorus. But this water never produces the thallus of mould, 

 and this, because it contains neither acid nor alkali, conditions 

 which are indispensable, as it would appear, to the production 

 of these thalluses. But this distilled water of lettuce produces 

 these thalluses when a little of any acid is added. And when 

 the distilled waters of plants contain an acid which passes over 

 with them during the distillation, they never fail to produce and 

 deposit at the bottom of the vessels which contain them thalluses 

 of mould. It is thus that I have observed them in the distilled 

 laurel {Prunus Laurocerasus) water, which contains, as is known, 

 hydrocyanic acid. 



These solutions of organic substances, which produce the 

 thalluses of mould without any addition of acid or of alkali, 

 assuredly owe this power to their naturally containing a free acid 

 or alkali, as also to this, that they have become acescent. This 

 last alternative is probably the case with the watery solution of 

 isinglass, which produces in such abundance the thalluses of the 

 monilia. I have, moreover, found that this solution, in which 

 these thalluses were developed, did not turn the vegetable blues 

 to red. But this is no sufficient proof that they did not contain 

 a free acid in a trifling quantity, sufficient, however, to deter- 

 mine the appearance of the thallus. I have, in fact, seen these 

 thalluses produced in albuminous water, to which I had myself 

 added a quantity of nitric acid, but so small that it did not red- 

 den the vegetable blues. 



The subcarbonate of potash, which exists in almost all vege- 

 table products, is alkaline, and probably contributes to deter- 

 mine the development of the thallus of mould in certain solu- 

 tions of vegetable substances. This alkaline salt being added 

 to albuminous water, it then readily produces this thallus. I 

 have proved that the bi-carbonate of potash produces the same 

 effect ; but it is to be remarked that this salt is scarcely ever . 

 neutral, the alkali invariably slightly predominating. It may 

 be asked, how it happens that the albumen of the egg^ which 

 contains a small quantity of soda, does not, in virtue of this in- 

 gredient, provoke the production of the thallus of mould in the 

 water to which it may be added ? To this it may be answered, 

 that the soda in the albumen is not in a free state ; but that, 



