40O COMPOUND PRODUCTS. CHAP. I. 



iiiained a portion that was insoluble. It had a 

 greasy appearance^ and became soft and viscid upon 

 exposure to air, assuming a brown colour with a 

 slight degree of transparency. When thrown upon, 

 ignited charcoal it melted, exuding drops of grease, 

 accompanied with a noise like that of meat roast- 

 ing, and producing smoke which had the odour of 

 volatilized fat. It left no residuum. This sub- 

 stance was vegetable fibrina possessing the proper- 

 ties of the fibrina of animals. 



SECTION VII. 

 Extract. 



Howob- WHEN vegetable substances are macerated in 

 water a considerable portion of them is dissolved ; 

 and if the water is again evaporated, the substance 

 held in solution may be obtained in a separate 

 state. This substance is denominated Extract. 

 But it is evident that extract thus obtained will 

 not be precisely the same principle in every dif- 

 ferent plant ; but will vary in its character accord- 

 ing to the species producing it, or the soil in which 

 the plant has grown, or some other accidental cause. 

 It was necessary therefore, for the purposes of che- 

 mical accuracy, to endeavour to ascertain whether 

 or not there existed in extracts any peculiar anjd 

 definite principle, independent of such accidental 

 ingredients as have been now alluded to ; and which 



