Microscopic Structure—The bark presents but few structural peculiarities. The ring of liber is made up of alternating prosenchymatous and parenchymatous tissue. In the latter the larger cells are filled with mucilage, the others with starch. The prosenchymatous groups of the liber exhibit that peculiar form we have already described as hornbast ([p. 74]); it chiefly contains the tannic matter, besides stellate crystals of oxalate of calcium which are distributed through the whole tissue of the bark. The medullary rays are of the usual form, and contain starch granules. The corky coat is built up of a smaller number of vaulted cells.
Chemical Composition[641]—The bitter principle of the bark has been ascertained by Broughton[642] to be a nearly colourless resinous substance, sparingly soluble in water but more so in alcohol, ether, or benzol. It does not appear to unite with acids or bases, and is less soluble in water containing them than in pure water. It has a very bitter taste, and refuses to crystallize either from benzol or ether. It contains no nitrogen. To this we may add that the bark is rich in tannic acid.
Uses—Rohun bark is administered in India as an astringent tonic and antiperiodic, and is reported useful in intermittent fevers and general debility, as well as in the advanced stages of dysentery and in diarrhœa.
RHAMNACEÆ.
FRUCTUS RHAMNI.
Baccæ Rhamni, Baccæ Spinæ cervinæ; Buckthorn Berries; F. Baies de Neprun; G. Kreuzdornbeeren.
Botanical Origin—Rhamnus cathartica L., a robust diœcious shrub with spreading branches, the smaller of which often terminate in a stout thorn. It is indigenous to Northern Africa, the greater part of Europe, and stretches eastward to the Caucasus and into Siberia. We have seen stems 50 years old, having a diameter of 8 inches, sent from the government of Cherson, Southern Russia. In England the buckthorn though generally distributed is abundant only in certain districts; in Scotland it occurs wild in but a single locality. Yet in Norway, Sweden, and Finland it grows much further north.
The fruit which ripens in the autumn is collected for use chiefly in the counties of Hertfordshire, Buckinghamshire, Oxfordshire, and also from Wiltshire. The collectors usually prefer to supply the juice as expressed by themselves.
History—The Buckthorn was well known to the Anglo-Saxons, and is mentioned as Hartsthorn or Waythorn in their medical writings and glossaries dating before the Norman conquest. The Welsh physicians of Myddfai (“Meddygon Myddvai”) in the 13th century prescribed the juice of the fruit of buckthorn boiled with honey as an aperient drink.
As Spina Cervina the shrub is referred to by Piero de’ Crescenzi of Bologna[643] about a.d. 1305.