ANALYSIS OF A VEGETABLE EXCRESCENCE. 143 



It is true, that we perceive this irritability only at a certain 

 age, and not in ell plants that have a peculiar juice. But are 

 we to presume, that, if this property do not manifest itself at 

 erery age, and in every plant, but only when it is extremely 

 exalted, and in those plants that are perhaps most endued 

 with it, other plants are destitute of it ? On the contrary we 

 may reasonably infer, that those vessels, which exhibit a great 

 deal of irritability at a certain period, and in certain plants, 

 possess at other times, and in other plants, a sufficient quan- 

 tity for the circulation of the fluids, though no excess of it 

 to be rendered sensible. 



But if it be reasonable to suppose, that the vessels con- and to all tbd- 

 taining the peculiar juice are endued with this irritability, ve 

 and that it is by this property the juice is compelled to cir- 

 culate in them ; who will venture to assert, that the vessels 

 of other systems are destitute of it, and that the circulation 

 ©f their respective fluids arises from a different cause, or is 

 occasioned by some other power? 



XII. 



Chemical Examination of some Vegetable Substances ; by 

 Mr. Vauquelin*. 



Sect, I. Chemical Examination of a vegetable excrescence 

 from Madagascar, sent to the Isle of France by Mr. Cha- 

 pcllier, and thence to Europe by Mr, Jannet. 



T. 



HIS substance is as white as a cake of starch ; it is 

 perforated in all directions by an immense quantity of egetabie ex- 

 holes formed by little insects ; it has neither smell nor taste ; Madagascar 

 it diffuses in burning the smell of burned bread, inclining a dGSCnb ^' 

 little to that of touchwood. 



1. Treated with a very large quantity of nitric acid, it fur- 

 nished a little oxalic acid, but no rnuric ; consequently it 

 contains no gum. 



2. Water ha» no action on it: but if it remains a long 



* Ana. d« Cbim. rol. lxxii, p. 297. 



time 



