312 M. Dutrochet's o?i the Origin of' Mouldiness. 



produce at pleasure. The various moulds have seeds, whose 

 diminutiveness is excessive, and which, scattered every where in 

 the atmosphere, and perhaps even contained in animal and ve- 

 getable liquids, develope themselves under the forms of fila- 

 mentous thallus, when they are placed in circumstances neces- 

 sary for their development. The presence then, of an acid or 

 of an alkali in an aqueous liquid containing some organic 

 matter, is thus nothing more but a condition of the development 

 of the thallus of mould. Experiment has proved the accuracy 

 of this theory, I have taken a small portion of the thallus of 

 mould, produced in an aqueous solution of isinglass, and I have 

 transplanted it into pure albuminous water, where it ceased to 

 grow. I have also put into pure albuminous water small por- 

 tions of the thallus of mould, which were taken from the albu- 

 minous water somewhat acid or somewhat alkaline ; and they 

 continued in it without any increase. These experiments have 

 proved to my conviction, that pure albuminous water is wholly 

 improper for the development of the thallus of mould ; and 

 that it is on this account that it never appears in this liquid 

 when left to itself This is also true of the albuminous water 

 united with the neutral salts. 



Mercury, whether in the state of a salt, or of an oxide, com- 

 pletely obstructs the appearance of the thallus of mould in 

 liquids where it is found. Thus, for example, the solution of 

 isinglass, which so abundantly produces it, will produce it no 

 longer, if to the solution we add the smallest quantity of red 

 precipitate or of corrosive sublimate. This property of mercury 

 is very remarkable, and gives rise to some useful applications in 

 the arts. 



Mercury in its metallic state, added to the water which holds 

 a little isinglass in solution, does not hinder the prompt produc- 

 tion of the thallus of mould ; the same is also true of the 

 (aethiops mineral) oxide of the black sulphurate of mercury. 

 The proto-sulphate of mercury (turbith mineral), completely 

 hinders the appearance of the thallus, as, in fact, do all the salts 

 of mercury. 



Observing how efficacious the oxide of mercury was in pre- 

 venting the production of the thallus, even when used in a dose 

 of the most minute quantity, I wished to try if there were not 



