38 ^^ VEGETABLE MUCILAGES. 



our principles, we should defeat the very end of arrangement. 

 Hence, in the formation of our essential characters, we must 

 epdeavour to adopt the due jnedium between the extremes 

 of minuteness and. laxity. In each particular instance we 

 must be guided by those propertied, which are the most dis- 

 dinctly recognized, and the most readily ascertained, and 

 which exliibit the closest analogy to each otlier. Under this 

 impression I shall not think it desirable, 'm tJie present state 

 of our knowledge, to proceed any farther in proposing an 

 additional number of primary vegetable compounds ; but 1 

 shall offer a few remarks upon the different mucilages, that 

 have been made the subject of experiment. 

 Generic clia- Gum T consider as a generic term, which may be defined 

 meters of gum. a transparent, brittle, insipid substance, indefinitely soluble' 

 in water, with which it forms a mucilaore; the mucilag^e is 

 precipitated by alcohol, in such a manner as to render the 

 fluid perfectly opake ; it is also precipitated by the acetate 

 of lead in dense flakes. Under this genus we can, at pre- 

 Species and sent, rank only one species, viz. gum arabic, to which the 

 following specific character may be applied. A gum, the 

 mucilage of which may be precipitated by silicated potash ; 

 forms with the oxysulphate of iron a solid jelly, with the ni- 

 trate of mercury a precipitate of a pink colour; and is not 

 acted upon by the superacetate of lead, the nitro-uiuriate of 

 tin, or the nitro-muriate of gold. 

 Generic cha- The second genus is mucus, a substance seldom found 

 racters of mu- in a separate state, but forming a frequent constituent of the 

 seeds, roots, leaves, and other parts of vegetables. It is 

 indefinitely soluble in water, and forms with it a mucilage ; 

 this is precipitated by alcohol in a fibmus form, without ren- 

 dering th€ fluid opake ; it is also precipitated by the acetate 

 of lead, the super-acetate of lead, and the nitro-muriate of 

 tin.. Under the genus of mucus we may enumerate three 

 Three species. ^P^pi^s, that of linseed, of quinceseed, and of the hyacinth. 

 To the first of these the generic character strictly applies ; 

 Specific cha- ^*^ to the second we maj^ add the specific character of being 

 racters. Qpagulated by the addition of any acid, neutral, earthy, or 



That of the metallic salt. The hyacinth mucilage I have also classed as 

 hyacinth a ^ mucus, because its leading properties are such as point 

 out its relatioji to the substances of this genus. In the state, 



however, 



