SECT. XXIX. GENERAL REMARKS. 4?5 



introduced under such a character; such as the 

 mucus, jelly, sarcocol, asparagin, inulin, and ulmin, 

 of Dr. Thomson, as described in his well known 

 System of Chemistry; but as there seems to be 

 some difference of opinion among chemists with re- 

 gard to them, and a belief entertained that they 

 are but varieties of one or other of the foregoing 

 ingredients,* it is sufficient for the purposes of 

 this work to have merely mentioned their names. 



Several other substances of a distinct and peculiar 

 character have been suspected to exist, and may 

 very possibly exist, in vegetable productions : such 

 as the febrifuge principle of Seguin, as discovering 

 itself in Peruvian Bark ; the principle of causticity 

 or acridity of Senehier,-}- as discovering itself in the 

 roots of Ranunculus bit I bos us, Scilla maritima, 

 JSryonia alba, and Arum rnaculatum, in the leaves 

 of Digitalis purpurea, in the bark of Daphne 

 Mezereon, and in the juice of the Spurges : to 

 which may be added the fluid secreted from the 

 sting of the common Nettle, the poisons inherent 

 in some plants, and the medical virtues inherent in 

 others ; together with such peculiar principles as 

 may be presumed to exist in such regions of the 

 vegetable kingdom as remain yet unexplored. The 

 important discoveries which have already resulted 

 from the chemical analysis of vegetable substances 

 encourage the hope that further discoveries will 



* Elem. of Agri. Chem. p. 104. 

 f Pbys. Veg, vol. ii. p. 408. 



