150 woop. 
ing mucilage, but insoluble in alcohol, which decomposes 
mucilage, combining with the water and precipitating the 
gum. The elements which enter into its composition are 
nearly in the following proportions :— 
Gay Lussac. BERZELIUS. 
Carbon, - a : 42,23 41.906 
Oxygen, - : : 50.84 51.306 
Hydrogen, .* ...< ... cs. 6.93 6.788 
100 parts. 100 parts. 
There is also present a small proportion of the carbonate 
and phosphate of lime, and it-has been lately said, some ni- 
trogen. 
584. Gum is obtained principally from the Acacia vera, 
§e.; the Plum and Cherry trees also contain it; and the 
Astragalus verus affords a peculiar kind of gum. 
585. Mucilage, or a substance resembling it much, is 
found in many vegetables,—as the Marsh-mallow, Quince- 
seed, Lichens, some Algw, bulbous roots, Linseed, &e. Gum 
and mucilage are very nutritious. They are also useful for 
thickening colouring matters to prevent them spreading 0D 
cloth, and enable them to be applied to it; hence they are 
much used in calico printing. The mucilage from Lichens 
has been employed for this purpose. 
F 3. starch (Fecula). 
586. This substance does not exist quite free in the ve 
getable, but as it can be easily separated from the principles 
_ with which it is associated, it may be considered as mechan’ 
cally mixed rather than chemically combined with them. To — 
___ procure it from wheat, the grain must be steeped in cold water 
till it becomes soft, and gives a milky juice when squeezed; i 
_ is then to be put into linen bags and pressed in water. 
_ milky juice which exudes contains the starch, which is 800? 
deposited in the form of a white powder. It may also be 
of water: when the fibrous parts have been removed, the 
