TRAGACANTHA. 177 



Vermicelli and Common or Soiis; this sorting is performed almost 

 exclusively by Spanish Jews. 



Description — The peculiar conditions under which tragacanth 

 exudes, arising from the pressure of the surrounding tissues and the 

 power of solidifying a large amount of water, will account to some 

 extent for the strange forms in which this exudation occurs. 



The spontaneously exuded gum is mostly in mammiform or 

 botryoidal masses from the size of a pea upward.s, of a dull waxy lustre, 

 and brownish or yellowish hue. It also occurs in vermiform pieces 

 more or less contorted and very variable in thickness ; some of them 

 may have exuded as the result of artificial punctures. It is this form 

 that bears the trade name of Vei^micelli. The most valued sort is 

 however the Flake Tragacanth, which consists of thin fiattish pieces or 

 flakes, 1, 2, 3 or more inches in length, bj'- :^ to 1 in width.' They 

 are marked on the surface by wavy lines and bands, or by a series of 

 concentric wave-marks, as if the soft gum had been forced out by 

 successive efforts. The pieces are contorted and altogether very variable 

 in form and size. The gum is valued in proportion to its purity and 

 whiteness. The best, whether vermiform or flaky, is dull-white, 

 tianslucent, devoid of lustre, somewhat flexible and homy, firm, and 

 not easily broken, inodorous and with scarcely any or only a slight 

 bitterish taste. 



The tragacanth of Kurdistan and Persia shipped from Bagdad, which 

 sometimes appears in the London drug sales under the incorrect name 

 of Syrian Tragacanth, is in very fine and large pieces which are rather 

 more translucent and ribbon-like than the selected tragacanth imported 

 from Smyrna : in fact, the two varieties when seen in bulk are easily 

 distinguishable. 



The inferior kinds of tragacanth have more or less of colour, and 

 are contaminated with bark, earth and other foreign substances. They 

 used formerly to be much imported into Europe, and were frequently 

 mentioned during the past centuries as black tingacanfh. 



Microscopic Structure — The transformation of the cells into 

 tragacanth is usually not so complete, that every trace of the original 

 tissue or its contents has disappeared. In the ordinary drug, the remains 

 of cell- walls as well as starch granules may be seen, especialh- if thin 

 slices are examined under oil or any other liquid not acting on the gum. 

 Polarized light will then distincly show the starch and the cell-walls. 

 If a thin section is imbued with a solution of iodine in iodide of 

 potassium and then moistened with concenti"at«d sulphuric acid, the 

 cell-walls will assume a blue colour as well as the starch. 



Chemical Composition — When tragacanth is immersed in water 



^ In the Museum of the Pharmaceutical and 5 inches in diameter, and bearing tra- 



>rjciety in London, there is some Flake Tra- gacanth. It is probable that the specimen 



gacanth remarkable for its enormous size, of gum we have described was produced by 



but in other respects precisely like the ordi- some species attaining these extraordinary 



nary kind. The ribbon-like strips are as dimensions. Among the Kurdistan traga- 



much as 2 inches wide and ^-^ of an inch canth, there occur curious cylindrical ver- 



thick, and the largest which is several inches miform pieces, about ^ of an inch in diameter, 



long weighs 2f ounces. Professor Hauss- coated with a net-work of woody fibre. We 



knecht has informed us that he has seen in are told by Professor H. that they are 



Luristan stems of Astragalus erimtylus picked out of the centre of cut-oflF pieces of 



Boiss. et Haussk. more than 6 feet in height stem, split open by rapid drying in the sun. 



M 



