TRAGACANTHA. 175 



Haussknecht has informed us that from this and the last-named 

 species, the so-called Aintab Tragacanth is chiefly obtained. 

 Probably the drug is also to some extent collected from 



9, A. varus Olivier, in North-western Persia and Asia Minor. 

 Lastly as to Greece, tragacanth is also afibrded by 



10. A. Parnassi Boiss., var. cyllenea, a small shrub found in abund- 

 ance on the northern mountains of the Morea, which is stated by 

 Heldreich^ to be the almost exclusive source of the tragacanth collected 

 about Vostizza and Patras. 



History — Tragacanth has been known from a very early period. 

 Theophrastus in the 3rd century B.C. mentioned Crete, the Peloponnesus 

 and Media as its native countries. Dioscorides, who as a native of 

 South-eastern Asia Minor was jjrobably familiar with the plant, describes 

 it correctly as a low spiny bush. The drug is mentioned by the Greek 

 physicians Oribasius, Aetius, and Paulus ^gineta (4th to 7th cent.), and 

 by many of the Arabian writers on medicine. The abbreviated form of 

 its name " Dragantum " already occurs in the book " Artis veterinarise, 

 seu mulomedicinse" of Vegetius Renatus, who lived about a.d. 400. 

 During the middle ages the gum was imported into Europe through the 

 trading cities of Italy, as shown in the statutes of Pisa,"' a.d. 1305, where 

 it is mentioned as liable to impost. 



Pierre Belon, the celebrated French naturalist and traveller, saw and 

 described, about 1550, the collecting of tragacanth in the northern part 

 of Asia Minor; and Tournefort in 1700 observed on Mount Ida in 

 Candia the singular manner in which the gum is exuded from the 

 living plant.* 



Secretion — It has been shown by H. von Mohl* and by Wigand^ that 

 tragacanth is produced by metamorphosis of the cell membrane, and 

 that it is not simply the dried juice of the plant. 



The stem of a gum-bearing Astragalus cut transversely, exhibits con- 

 centric annual layers which are extremely tough and fibrous, easily tearing 

 lengthwise into thin filaments. These inclose a central column, radi- 

 ating from which are numerous medullary rays, both of very singular 

 structure, for instead of presenting a thin-walled parenchyme, they 

 appear to the naked eye as a hard translucent gum-like mass, be- 

 coming gelatinous in water. Examined microscopically, this gummy 

 substance is seen to consist not of dried mucilage, but of the very 

 cells of the pith and medullary rays, in process of transformation into 

 tragacanth. The transformed cells, if their transformation has not 

 advanced too far, exhibit the angular form and close packing of paren- 

 chyme-cells, but their walls are much incrassated and evidently consist 

 of numerous very thin strata. 



That these cells are but ordinary parenchyme-cells in an altered 

 state, is proved by the pith and medullary rays of the smaller branches 

 which present no such unusual structure. Mohl was able to trace 

 this change from the period in which the original cell-membrane could 

 be still easily distinguished from its incrusting layers, to that in which 



^ Nutzpflanzen Griechenlands, Athen, '^ Voyage into the Levant, 'LonA.{\1\%) 43. 



1862.71. * Botanische Zeitwiff, l8o7 . 33 ; Pharm. 



2 Bonaini, Siatuti mediti ddla cittA di Jouni. xviii. (1859) 370. 



Pissa dal xii. al xiv. secolo, iii. (1857) 106. ^ Pringsheim's Ja A rfeiicAer/. wissenchaftl. 



114. Boiaml; iii. (1S61) 117. 



