MILK VETCH.

1139

Fig. 210.

Astragalus criticus.

*0,

re.

-A. creticus.—F lowers axillary, sessile, clustered. Calyx five-partite, with feathery, setaceous lobesrather longer than the corolla. Leafletsfive to eight pairs, oblong, acute, tomentose(D. C.) — Mount Ida, in Crete , where ityields Tragacanth, according to Toumef’ort.

Production. —Tragacanth is a naturalexudation from the stem of the before-mentioned plants. The cause of the exu-dation of this as of other gums, is thusexplained by Decandolle ( Phys. Veg. t. i.)The gummy matter of the stem resides inthe bark and alburnum; it is the nutritivejuice of the plant; and its escape, there-to ’ 1S anal °8° us to hemorrhage in animals: hence plants in whom itCa ntane °usly occurs are always in a sickly state. The mechanicaliH e . S ? °f the expulsion of this juice is dependent on the unequal hygro-tnoj. 110 properties of the different parts of the stem. The wood absorbs(• 0tl e rooisture from the air than the bark, and hence it swells more. In'UU e SeC1Uence rts enlargement, it distends the bark, which, by the^hi$ na ^ P ressure °f the wood, gives way, and the gummy matter escapes.l^jj^Planation is quite in conformity with facts mentioned by La Bil-

4 j- . re >~~~that tragacanth flows only in abundance during the night, andn 6c e a fter sunrise. A cloudy night, or a heavy dew, is, he thinks,

s * ar y for its production; for the shepherds of Lebanon only go inftio-v., ^ this substance when the mountain has been covered during the"hh thick clouds.

the ^ Scrii, tion. —Tragacanth [gummi tragacantha ) is frequently called in

5 a °p s gum dragon. It is white, yellowish, or yellowish-brown, hard,iiei ’ 0f h J urle.ss, tastek

th:

tasteless, swelling considerably in water, and forming a

>ck t • 5

1 ac '°us mucilage. Two kinds of it are known,

o/ „ L Axr Tragacanth .- Smyrna Tragacanth (Mai'tius) : TragacanthpH,,)■ e , ragalus verus ?—This is the tragacanth usually found in

fri a S a commerce. It occurs in moderately large, broad, thin pieces,

2 ea ; with arched or concentric elevations.

VdhtJt Er miform Tragacanth .- Morea Tragacanth (Martius): Traga-’hi s ^e Astragalus creticus ?—This variety is rarely met with inSentry, but is common on the continent. It occurs in small,

’.Aliform, spiral pieces. There is more starch in it than in the^ ' a nety.

a Ud nof KRce -'—Tragacanth is imported in cases and chests from Smyrnaer ports of the Levant. In 1839, duty (6s. per cwt.) was paid£ cwts.

by ^j^FosiTION .-—The ultimate analysis of tranraeanth has been made

er mann and by Guerin-Varry ( Journ. de C'hirn. Med.

s beenvii. 742).

o ar bonrv ^di*og> €

Hermann’s Analysis.

Atoms.

Eg. Wts .

Per cent.

.... 60 ..

. 40-50

n .10

.... 10 ..

. 6 61

... 80 ..

. 52-89

cau *li gum 1

.... 150 ..

.. 10000

Guerin - Varry’s Analysis.

Insoluble ditto.

35-797-11

Soluble part,.. 42 01

.. 642

.. 54-57

103-00

5710

100 00