NAT. ORDER. LEGUMNOSjE. 
151 
harvest, of the journey, and of the fair, the Moors of the desert hve al- 
most entirely upon it ; and experience has proved that six ounces are 
sufficient for the support of an adult during- twenty-four hours. 
Medical Properties and Uses. The characters g-enerally g-iven of 
gum as a veg-etable principle, belong" only to the g-um-arabic, which is 
transparent and colorless, easily reduced to powder, without smell, 
and of a slig-htly sweetish taste. The solution of g-um in water con- 
stitutes mucilag-e. It is thick and adhesive, and soon dries when ex- 
posed to the air. Gum is also soluble in weak acids, but is totally in- 
soluble in alcohol. Gum is very little disposed to spontaneous decom- 
position. By oxyg-enizement with nitric it forms successively mucic, 
malic, and oxalic acid ; with oxymuriat acid it forms citric acid. By 
exposure to heat it does not melt, but softens, swells, and becomes 
charred. 
In medicine, g"um-arabic possesses the powers of mucilag-inous 
demulcent in a high degree. It is useful in all cases where there 
seems to be a natural deficiency of mucus in the intestinal canal. — 
Dissolved in milk, barley-water, or almond emulsions, it removes tenes- 
mus. It is useful in an irritable state of the respiratory passages, in 
catarrh, hoarseness, and cough. For this purpose it may be either 
administered in substance as a troche, or in a strong solution, and may 
be combined with a little opium. It is also useful in salivation after 
mercury, or in small pox. Externally it is applied in powder to bleed- 
ing vessels of a small size as a styptic, operating by glueing them up. 
It is also used in solution as an injection in gonorrhoea. 
