Lx'erlnenti on the A 



(2310 grains Englifh) per myriagramme (z2 fibs. 1 ounce) 

 of wood, vvhiie the poplar furmllies 72 (11,088 grams.) 

 To what is it indebted ibr this quantity? An aniwer to this 

 queftion will he found hy analyzing its fap< Idle acrid and 

 vifcous juice of its buds, ufed in pharmacy, will alfo furniih 

 iome data. 



A myriagramme (22 libs.j ounce, avoirdupoife) of the po- 

 fuhis tremiila (trembling poplar) furnifhea only 7 grammes 

 (107S grains) of faline matter, as appears by a calculation 

 made from a very accurate experiment*. This difference, 

 more than decuple, in faline matter between one tree and 

 another of the fame fpeeies,wil! aitonim only thofe who do not 

 know that the rhubarb and forrel are of the fame genus, and 

 that the four cherry belongs to the fame fpecies as the com- 

 mon wild-cherry. Nature is not confined to our narrow ideas 

 of analogy. It has been laid down as a principle, that plants 

 of the fame family may mutually fupply each others place in 

 medicine, but it is prudent to apply this principle only after 

 a very accurate analyfis of the plant employed, and that in- 

 tended to be fubftituted for it. 



2d, It follows from the firft five experiments, that rotten 

 wood gives more allies than found wood, often more than 

 double, which may be readily conceived. Wood by rotting 

 becomes fpongyand light. I have feen fome which weighed 

 a half lefs, under an equal volume, than found wood of the 

 fame tree. It burns without flame like tinder, and is diffi- 

 cult to be incinerated. It appears that the hydrogen has 

 "been almoft deftroyed, and that the carbon concealed by the 

 earthy parts efcapes combuftion. This wood is often phof- 

 phorefcent, a phenomenon the caufe of which is yet un- 

 known. Rotten wood mutt not be confounded with that 

 which is pierced by worms. In the latter cafe the wood 

 without changing its colour is reduced to an impalpable 

 powder, and in the fmall part which remains folid is found 

 the orifice the worm has formed, and often the worm itfelff. 

 A hundred parts of a vine twig reduced to an impalpable 



• Ann de Cbimie, vol. xix. p. 178. I did not extract the faline mat- 

 ter from the poplar, as the-eftimarion by exhauftion appeared to me more 

 certain, becaufe it is difficult to bring back the faline matter always to the 

 d point of calcination. But having calculated, that the afhes of the 

 lofes in lixiviation o'i6, and gives in faline matter 0*13, I deducted 

 &h», or o'ly, for the lots by lixiviation, and I think 1 obtained nearly 

 prodp£fc in faline matter, this difference arifes from the carbonic acid 

 which the faline matter lofes in calcination. 



This worm differs according to the wood, the phalana 'ofus, larva of 

 the goat-moth, a delicate morfel among the ancients, which no modern 

 ■turc to tafte, is found in old trunks of the oak. 



powder* 



