Yellow bark. This bark, very lately introduced into practice, is supposed to be a species of cinchona, growing in the interior mountainous parts of America, described by Murray under the title of cortex chinae, vel chinchinae regius, seu cortex chine flavus. This bark, according to Murray, consists of flattish pieces of about the length of a finger, the breadth of the thumb, and a line in thickness. Its colour is yellowish, inclining to that of the red oxide of iron. It partakes more of the ferruginous colour on its external than on its internal surface, owing to the close adhesion of the epidermis to the bark. Both in its fracture and on its surface it appears fibrillous, breaking easily between the fingers, so that it may be rubbed into a yellow powder. In taste it is intensely bitter, with a slight degree of astringency. Its efficacy is considered as far superior in intermittent fevers to the bark commonly employed. Dr. Relph observes, that in colour it only approaches nearer to a yellow than any other species of Peruvian bark imported into this country, especially when reduced to powder; that it consists of flattish irregular pieces, of a cinnamon colour, inclining to red, having, in certain directions of the light, a peculiar sparkling appearance on the surface. The pieces are very generally divested of the cuticle, of a fibrous texture, dry, and rigid to the feel, easily rubbed to powder between the finger and the thumb; not remarkable for their specific gravity. They have little odour, but to the taste are intensely bitter, with a moderate share of astringency, and a flavour corresponding unequivocally to that of the cinchona officinalis. The external surface of this bark is somewhat of a deeper colour than the internal, and in some specimens it is as deep as that of the red bark. The pieces vary much in size; some are about two inches and a half in length, an inch in breadth, and the sixth of an inch in thickness; while others are still smaller; and some are to be found from twelve to eighteen inches in length, with the breadth and thickness in proportion. Pieces sometimes through the whole chest are nearly cylindrical, and as completely covered with an outer coat as the most perfect specimen of common bark. The epidermis of the large pieces of the yellow bark is of a reddish brown colour, rough, and of a somewhat spongy texture; but that of the smaller pieces is grey, harder, and much more compact.

Like the cortex Peruvianus, it yields its virtues to water by infusion or decoction, to proof or rectified spirits, and extracts may be formed from either in the usual way. It is considered to possess the same virtues, but in a greater degree than either the common or red bark, consequently to be more efficacious in smaller doses. For the complaints to which it is adapted, see Cortex Peruvianus: the dose of the powder is from Эss. to Э ij.-of the extract half the quantity is sufficient. See Relph on the Yellow Bark.