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Besides the principles, the nature of which has 

 been just discussed, thers have been described by- 

 chemists as belonging to the vegetable kingdom : thus 

 a substance, somewhat analogous to the muscular 

 fibre of animals, has been detected by Vauquelin in 

 the papaw ; and a matter similar to animal gelatine by 

 Braconnot in the mushroom ; but in this place it 

 would be improper to dwell upon peculiarities ; my 

 object being to oier such general views of the consti- 

 tution of vegetables as may be of use to the agricul- 

 turist. Some distinctions have been adopted by sys- 

 tematical authors which I have not entered into, be- 

 cause they do not appear to me essential to this enquiry. 

 Dr. Thomson, in his elaborate and learned system of 

 chemistry, has described six vegetable substances, 

 which he calls mucus, jelly, sarcocol, asparagin, inu- 

 lin, and ulmin. He states that mucus exists in its 

 purest form in linseed ; but Vauquelin has lately 

 shewn, that the mucilage of linseed is, in its essential 

 characters, analogous to gum ; but that it is combin- 

 ed with a substance similar to animal mucus : vegeta- 

 ble jelly, Dr. Thomson himself considers as a modifi- 

 cation of gum. It is probable, from the taste of sar- 

 cocol, that it is gum combined with a little sugar. 

 Inulin is so analogous to starch, that it is probably a 

 variety of that principle ; ulmin has been lately shewn 

 by Mr. Smithson to be a compound of a peculiar ex- 

 tractive matter and potassa ; and asparagin is proba- 

 bly a similar combination* If slight differences in 

 chemical and physical properties be consided as suffi- 

 cient to establish a difference in the species of vegeta- 

 ble substances, the catalogue of them might be enlar- 



