812

ELEMENTS OF MATEEIA MEDICA.

Those which extend only to the centre, have been evidently madethe purpose of examining the condition of the interior of the pieces. ,Externally the pieces are covered with a bright yellovv-eot 0 ^^powder, usually said to be produced hv the mutual friction of the pjin the chests, during their passage to this country; though many 1 °

gists believe it is derived from the process of rouncing (that is, s ‘ ia j sin a bag with powdered rhubarb), before its exportation. Thestrong and pecidiar, but somewhat aromatic ; it is considered by < n .’ D j) e pt

to be so delicate, that in all wholesale drug-houses a pair of gloves i*in the llussian rhubarb drawer, with which only are the assistants I,mitted to handle the pieces. When chewed it feels gritty

pieces. YVlien chewed it teeis gritty under ^teeth, from the presence of numerous crystals of oxalate of lime •' d ®niunicates a bright yellow colour to the saliva, and has a bitter, slig 1astringent taste. , g a

Beneath the dust with which the pieces are covered, the surface 11 ^reddish-white tint, owing to the intermixture of white and red P a j rThe yellowish-wliite parts have the form of lines or veins, which, by 1 junion with each other, assume a reticular form. Irregularly scatt 0 f aover the surface we observe small star-like spots and depressions,^darker colour. The transverse fracture is uneven, and presents numet ^brownisli-red or dark carmine-coloured undulating veins. The l° n ". )Udinal fracture is still more uneven, and shows the longitudinal di feC ■of the veins, which are often interrupted with white- The surfaceis more or less yellow, and often exposes the' e

tabled by cuttindisposed in groups

Fig. 173.

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By boiling very thin slices of the root in water,then submitting them to the microscope, we observelular tissue, annular ducts, and numerous conglo^^raphides (clumps of crystals of oxalate of lime). “ .j100 grains of Russian rhubarb, Mr. Quekett p r ° c ’ abetween 35 and 40 grains of these raphides (B 11 ) 1 ,Introd. to Botany, 3d ed. p. 553). Turpin conside^the presence of these crystals sufficient to distmgRussian and Chinese rhubarb from that gro" ’* , r pEurope ; but in some specimens of English rhuI have met with these crystals in as great abunmas in foreign rhubarb. According to Raspail (fOrgan.) these crystals are situated in the intersticethe elongated cellular tissue; but this stateuid 1erroneous, the situation of the crystals being 111interior of the cells. . , a

The powder of Russian rhubarb is of a bright yellow colour, vV1 ^ e Jreddish tint; but, as met with in the shops, it is almost invariably t* 11 'with the powder of English rhubarb.

White or Imperial Rhubarb .—When Pallas was at Kiaclita, thecharian merchants who supplied the crown with rhubarb, brought s .pieces of rhubarb as white as milk, with a sweet taste, and the salB f j )( ,tperties as rhubarb of the best quality ( Voyages , t. iv. p. 218). It lSmet with in English commerce as a distinct kind ; and it is ahn° sknow'll in Russia (Grassmann , Fharm. Central-Blatt fur 1831, b- ^But in the chests of Russian rhubarb there are occasionally found P 1C

Crystals of Oxalateof Lime in RussianRhubarb.

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