412 ORD. XXIV. Papilionacee. ASTRAGALUS TRAGACANTHA. 
described by Tournefort, and consequently not the Tragacantha 
of Linneus.* He also contradicts the opinion of Tournefort, who 
attributes the flowing of the gum to the contraction of the fibres _ 
of the bark, occasioned by the intensity of the solar heat; ob- 
serving that it is only during the night, or when the sun is obscured 
by clouds, that the gum issues from the plant, and that the same 
has been remarked at Crete. 
“ Gum Tragacanth differs from all other known gums, in giving 
a thick consistence to a much larger quantity of water;* and in 
being much more difficultly dissoluble, or rather dissolving only 
imperfectly,” Put into water, it slowly imbibes a great quantity 
of the liquid, swells into a large volume, and forms a soft but not 
fluid mucilage: if more water be added, a fluid solution may be 
obtained by agitation, but the liquor looks turbid and wheyish; 
and on standing the mucilage subsides, the limpid water on the 
surface retaining little of the gum:”+ nor does the mixture of 
gum arabic promote their union. 
The demulcent qualities of this gum are to be considered as 
similar to those of gum arabic:* it is seldom given alone, but 
frequently in combination with more powerful medicines, espe- 
cially in the form of troches, for which it is peculiarly well adapted. 
It gives name to an officinal powder, and is an ingredient in the 
compound powder of ceruss. 
* He makes the following distinctions: The stem of the Cretan Astragalus is 
blackish, that of Lebanon is yellow; the leaves of the first are downy, of the second 
they are smooth. The flowers of one are red, those of the other are of a’pale 
yellow. From hence he infers that there are various species of Astragalus which 
produce gum tragacanth, 
* Multo fortius est hoc gummi, quam G. arabicum, sc. ut 1 ad 24, Etenim 
dum G. Tragac. scrup. 8 aque pure libr. 2 in consistentiam Syrupi redigunt, re- 
quiruntur G. Arab. unc. 8 ad eundem effectum prestandum. Berg. M. M. p. 622. 
« Rutty asserts, that in five or six hours it will dissolve in cold water, Observ. 
en the Lond. & Edinb. Dispen. p. 179. + Lewis’s M. M. 
* See p. 189. Bergius says, Virtus: demulcens, obtundens, incrassans. CUsus: 
Dysenteria, Diarrhea, Stranguria. J. c. ps 621. 
