PHYSIOLOGICAL CLASSES OF MEDICINES.

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men, and other principles, though it may hold good to a certain extentwith respect to the oils.

Emollients are used to prevent the action of irritating matters on thebody, by involving them, or by sheathing or defending surfaces from theaction of substances capable of acting injuriously. When used for thesepurposes they are denominated demulcents (demulcentia , from demulceo,to mitigate or soften) . Thus we administer them when acrid poisonshave been swallowed. They are applied externally in the form oflocal baths, poultices, fomentations, &c. both as emollients and de-mulcents, in local inflammations, painful ulcers, &c. In irritation,inflammation, and ulceration of the alimentary canal, (as in gastritis,enteritis, diarrhoea, dysentery, &c.) they are taken either by themouth, or in the form of clyster. In catarrh, peripncuinony, and pul-monic affections in general, where the cough is dry and harsh, and theexpectorated matters are acrid, the use of emollients is often attendedwith very beneficial effects. By their lubricating and soothing influenceon the nerves distributed to the fauces, they probably affect the bron-chial membrane and pulmonic structure by a reflex action. In affectionsof the urinary passages, as ardor urina), emollients (especially aqueousfluids) are very serviceable.

Emollients may be arranged in the following groups:—

a. The first group contains water, the principal and most importantsubstance of the class. In order, however, that it may act as an emol-lient, it must have a certain temperature ; for neither very cold norboiling water has any emollient effect. Dr. Cullen fixes 62° F. as thelowest temperature at which this fluid can be emollient; and observes,that the greater its warmth the greater will be its emollient power, pro-vided that pain or scalding be not produced. Aqueous vapour is for tworeasons more emollient than liquid water : in the first place it penetratesthe organic tissues more powerfully; and, secondly, a greater degree ofheat can be applied by it than by liquid water. Dr. Cullen was doubtfulwhether advantage could be gained by any addition made to water.

b. The second group contains the mucilaginous emollients. Thisgroup has been subdivided into the pure mucilaginous emollients (as gumarabic, tragacanth, mallow, marshmallow, &c.), the sweets (as figs), thebitters (as Cetraria islandica, coltsfoot, and sarsaparilla), and the oily (aslinseed, sweet almonds, poppy seeds, &c.)

c. The third group embraces the farinaceous or amylaceous emollients;as wheaten flour, oatmeal, barley, arrow-root, sago, tapioca, ordinarystarch, &c.

d. The fourth group consists of the saccharine emollients ; as ordinarysugar, honey, liquorice, &c.

e. The fifth group includes the waxy, fatty, and oily emollients ; suchas the animal fats, &c. (as lard, mutton suet, butter, wax, and spermaceti),and the vegetable oils (as olive, almond, sesami, palm, poppy, linseed,See.)

f. The sixth group contains the albuminous emollients ; as the whiteand yelk of eggs, and milk. Saliva and gastric juice are employed onthe continent for medical purposes.

g. The seventh group comprehends the gelatinous emollients; asgelatine in its pure form, isinglass, hartshorn shavings, See.

Class 5, Refrigerants or Temperants.— Under this head are in-