TRAGACANTHA. 175 



L 



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

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

 Probably the drug is also to some extent collected from 



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

 Lastly as to Greece, tragacanth is also afforded 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 Srd century B.C. mentioned Crete, the Peloponnesus 

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

 South-eastern Asia Minor was probably 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 mulomedicinje" of Yegetius 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 



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



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

 hvmrr plant.' 



Secretion 



H. von Mohl * and by W 



- "o«-v.aiii,u IS proaucea Dy metamorpnosis oi tne ceii memuraue, auu 

 tlmt 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 

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

 atnig 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 



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

 ^fagacanth. The transformed cells, if their transformation has not 



J^vanced too far, exhibit the angular form and close packing of paren- 



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



numerous very thin strata. , ^ 



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



Jte IS proved by the pith and medullary rays of the smaller branches 

 thi k P^^^^nt no such unusual structure. Mohl was able to trace 

 , Change from the period in which the original cell-membrane could 



ily distinguished from its incrusting layers, to that in which 



186o'^"','^-^""^« Griechenlands. Athen, » Voy<^ge into the Levant, Lond. (1718) 43. 



-^' '^- i Botanische Zeifwifj, \S57. S3; Pharm. 



^ 'ii'iii easi 



'A' 



^•Ma'T/"''- *''"'"^*' *««<^''« (^e^?« cittd dl Journ. xviii. (1859) a70. 



m '^'' ^^i- al xiv. secolo. Hi (1857)100 spj^ingsheim'aJnhrbiicherf.wiSsenchaJtL 



Botanik, iii. (1 SGI) 117. 



