CORTEX LARICIS. 611 



CORTEX LARICIS. 



Larch Bark. 



Botanical Origin — Pinus Larix L. — see p. 609. 



History — The bark of the larch has long been known to possess 

 astringent properties; hence it has been used in tanning. Gerarde/ who 

 wrote near the close of the 16th century, likened it to that of the pine, 

 which he described to be of a binding nature; but there is no evidence 

 that it was an officinal druof. 



About the year 1858 larch bark was recommended by Dr. Frizell of 

 Dublin, and afterwards by other physicians, as a stimvilating astringent 

 and expectorant. In consequence of the favourable effects which have 

 resulted from its use it has been included in the Additions to the Phar- 

 macopoeia of 1867. 



Description — The bark that we have seen is in flattish pieces or 

 large quills, externally reddish-brown. In those taken from older wood 

 there is a large amount of an exfoliating corky coat, displaying as it is 

 removed bright rosy tints, while the liber is of a different texture, slightly 

 fibrous and whitish. The inner surface is smooth and of a pinkish-brown, 

 or pale yellow. The bark breaks with a short fracture, exhaling an 

 agreeable balsamic terebinthinous odour; it has a well-marked astringent 

 taste. For medicinal use the inner bark is to be preferred. 



Microscopic Structure — A transverse section exhibits resin-ducts, 

 but far less numerous than in the bark of many allied trees. The 

 medullary rays are not very distinct. Throughout the middle layer of 

 the bark large isolated thick-walled cells of very irregular shape are 

 scattered. 



Chemical Composition — Larch bark has been examined by Sten- 

 house,^ who finds it to contain a considerable amount of a peculiar 

 tannin, yielding olive-green precipitates with salts of iron. The same 

 chemist also discovered* in larch bark an interesting crystallizable 

 substance called Larixin or Lai^inic Acid, which has the composition 

 Q10JJ10Q5 j^ jj^g^y ^g obtained by digesting the bark in water in 80° C. 

 and evaporating the infusion to a syrupy consistence. From this, by 

 still further cautious heating in a retort, the larixin may be distilled, 

 during which operation some of it crystallizes on the inner surface 

 of the receiver, the remainder being dissolved in the distilled liquor. 

 From the latter it may be obtained in crystals by evaporation. The 

 substance forms colourless crystals, sometimes as much as an inch long; 

 it volatilizes even at 93° C, and melts at 153°. It requires about 88 

 parts of water for solution at 15° C, but more freely dissolves in boiling 

 water or in alcohol. From ether, in which it is but sparingly soluble, 

 it separates in brilliant crystals. The solutions have a bitterish astrin- 



pentine and another of common turpentine ^ Herhall, enlarged hy Johnson, Lond. 



be spread on two sheets of paper it will be 1636. 1366. 



found after the lapse of some weeks that ^ Proceedings of the Royal Society, xi. 



the former cannot be touched without ad- (1862) 404. 



herin^ to the fingers, while the latter will ' Phil. Trans., vol. 152 (1862) 53.— *We 



have become a dry, hard varnish. write the name Larixin instead of Larixine, 



with the concurrence of Dr. Stenhouse. 



