720

ELEMENTS OF MATERIA MEDICA.

ether, and the oils both fixed and volatile. Submitted to distillation? _yields an acid liquor [pyroligneous acid), and a volatile oil ( oil ofthe residue in the still is jntch. Oil of tar is brownish, and cons 1 "of oil of turpentine, impregnated with pyrogenous oil and resin. .

Composition. —Vegetable tar consists of several pyrogenous re& Jcombined with acetic acid, of colophony, oil of turpentine, and pyrofltoil. The liquidity of tar is owing to the two last-mentioned constitue nwhich hold the resins in solution (Berzelius , Traite de Chim. t*p. 680). 0 f

Physiological Effects. —The effects of tar are analogous to T 08 ®.turpentine, but modified by the presence of acetic acid and the p)genous products. Locally it acts as a stimulant, and, when apph echronic skin diseases and indolent ulcers, it frequently induces a sainchange in the action of the capillary and secerning vessels, evincedthe improved quality of the secretions, and the rapid healing of the s° ,In such cases it is termed detergent, digestive, or cicatrisant.lowed, it acts as a local irritant and stimulant, becomes absorbed, astimulates the secreting organs, especially the kidneys, on whi^^operates as a diuretic. Slight (YVibmer, Wirk d. Arzneim, Bd. iv. S-states that a sailor swallowed a considerable quantity of liquid ^which caused vomiting, great lassitude, and violent pain in bowelskidneys. The urine was red, and, as well as the other evacuations, gthe odour of tar. The head and the pulse were unaffected.vapour of tar, inhaled, acts as a stimulant and irritant to the bron cmembrane, the secretion of which it promotes.

Uses. —Tar is rarely employed internally. It has, however,administered in chronic bronchial affections, and in obstinatediseases.

The inhalation of tar vapour was recommended by Sir AleX aI * 'jCrichton [Pract. Observ. on the Treatm. and Cure of several vari^ iePulm. Consump. and on the Effects of the Vapour of boiling Tar * n $Disease, 1823) in phthisis ; but at best it can prove only a palliative, git frequently, perhaps generally, fails to act even thus, and in some ta ?occasions a temporary increase of cough and irritation (Dr.

Transl. of Lacnnec’s Treat, on Diseases of Chest, p. 365). In c ^ r ° o0 dlaryngeal, and bronchial affections, it has more chance of doing S(Trousseau and Pidoux, Traite de Therap. t. i. p. 459). The mode of u star fumigation I have before described (p. 51). kiU

Applied externally tar is used in various forms of obstinatediseases, especially those which affect the scalp, lepra, &c. ( jps

Administration. —Internally, tar is administered in the form 01 j^ymade up with wheat flour, or in that of electuary, with sugar. 1be taken to the extent of several drachms daily. r j-

1. Aqua Picis liquidje, D., Tar Water. —(Tar, Oij.; Water,

Mix, stirring with a stick for a quarter of an hour ; then, as soontar subsides, strain the liquor, and keep it in well-stopped jam)- g je.water has the colour of Madeira wine, and a sharp empyreumatic ^ ^It consists of w ater holding in solution acetic acid, and pyrogen , 0 pand resin. Notwithstanding the high eulogies passed on it by tf a ( e r)>Berkeley (Siris: A Chain of Phil. Reflex, and Inq. concern. Tar ^ jj»tar water is now rarely employed. It is occasionally adminismchronic, catarrhal, and nephritic complaints, to the extent of one

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