PHYSIOLOGICAL CLASSES OF MEDICINES.

75

placing a little benzoin or tolu in some live coals, and allowing thevapour to escape into the room : or the patient may inhale the vapour ofboiling water to which a drachm or two of the balsams have been added.

c. Foetid or .antispasmodic gum-resins (gummi-resinmfcetidd). The gum-resins, usually denominated foetid or antispasmodic, are asafcetida,ammoniacum, galbanum, sagapenum, and opoponax, all of which areobtained by incision from plants of the order Umbelli/eree, growing, forthe most part, in Persia . They are composed principally of gum andresin, but with a small quantity of volatile oil, to which they are mainlyindebted for their odour. Rubbed with w r ater, they form a milky fluidor emulsion. They are not completely soluble in pure alcohol, thoughthey form therewith a clear tincture, which becomes milky on theaddition of water, by the precipitation of the resin as a white powder.They dissolve, however, in boiling dilute alcohol. They are likewisesoluble in vinegar. Their odour is strong and remarkable; their tastewarm and acrid. Applied to the skin they act as mild stimulants.Taken internally they give rise to a sensation of warmth in the stomach,and cause eructations. The odorous particles of asafcetida becomeabsorbed, and may be recognised in the blood and secretions. Thefoetid gum-resins have been principally, and most successfully, employedin hysteria, flatulent colic, spasmodic asthma, chronic bronchial affec-tions, and in uterine disorders. From their beneficial influence in thefirst of these diseases, they are inferred to possess a power of specificallyaffecting the nervous (the true spinal) system.

Myrrh is a gum-resin procured from a plant of the order Burseracea.It does not possess the antispasmodic power of the foetid gums, butapproaches nearer to the tonics.

Olibanuin is also a gum-resin obtained from the same order asmyrrh. Its stimulant properties are principally directed to the mucousmembranes; and, in this respect, it is analogous to the resins, or ratherto the oleo-resins.

e. The fifth group includes ammonia and its salts, the empyreumaticoils, phosphorus, musk, and castoreuin. It is termed by Vogt ( Lehrb.d. Pharmakodyn.) volatile nervines {nervinia volatilia). All the substancesof which it is composed agree in producing a primary and specific effecton the nervous system, the energy and activity of w hose functions theyexalt. According to Vogt {op. cit. Bd. i. p. 186) the more volatile theremedy, the more it increases the activity of tire nervous functions, andthe more fixed, the more it raises their energy. Thus, according to thesame waiter, the preparations of ammonia raise the activity more than theenergy of these functions ; the empyreumatic oils somewhat less; muskstill less; while castoreum increases the energy of the functions princi-pally. However, I shall hereafter show that the last-mentioned remedyreally possesses very little power.

These remedies act as excitants to the organs of circulation, increas-ing the force and frequency of the pulse, augmenting the warmth of skin,and promoting diaphoresis. On account of the latter effect they havebeen termed diaphoretica calida. Though the particles of some of thempass into the blood, yet the constitutional effects cannot be regarded, inall cases, as the result of absorption, since, in several, they occur toospeedily to admit of this conclusion. And, as these effects are notalways proportionate to the local irritation and pain produced, they