This has already been considered as a nervous stimulant. When its oil is absorbed, it passes out by the kidneys, as well as other emunc-tories, and sometimes operates with considerable activity as a diuretic. it may be used in dropsy, under the same circumstances as horse-radish and mustard; and, moreover, in cases of that disease associated, as it not unfrequently is, with chronic bronchitis, in which garlic sometimes acts usefully as a stimulating expectorant. it may be administered in substance, bruised, or in the form of syrup. (See Allium, i. 6G9.)

The pollen of flowers, collected by bees, and deposited in the comb, along with honey, as food for the young bees, and commonly known by the name of bee-bread, has been found, by Dr. J. S. Whitmire, in the dose of a drachm, three times a day, to be powerfully diuretic. (Am. Journ. of Pharm., Jan. 1866, p. 56; from Chicago Med. Examiner, Sept. 1865.)

Class IV. Diaphoretics, or Sudorifics.

Diaphoretics are medicines which increase perspiration. This secretion is always going on in health, though, in consequence of the vaporization of the liquid at the moment of elimination, it is ordinarly insensible. Any one may convince himself of this, by holding the palm of his hand against a window-pane, in cold weather. The glass quickly becomes covered with the condensed moisture. Whether the perspiration shall be insensible, or sensible in. the form of sweat, depends partly on its quantity, and partly on the condition of the atmosphere in relation to moisture or dryness. When the air is very dry, the perspired fluid is instantaneously evaporated after extravasation, and, though possibly in considerable quantity, is quite insensible. On the contrary, in a very moist condition of the atmosphere, the escape of the prespiration in the aeriform state may be entirely prevented, and, even without any increase of secretion, the surface of the body may be bathed in sweat. There is consequently no difference in the function in these two opposite states of the surface; and the division formerly made of this class of medicines into diaphoretics which promote the insensible, and sudo-rifics which promote the sensible perspiration, is without any foundation in fact.

1. Mode Of Operation

Diaphoretics may operate either by stimulating the perspiratory function, or by relaxing the vessels of the surface, or by both methods jointly. They also operate by increasing the flow of blood through the skin, and the fulness of the blood-vessels.

1. By Stimulating the Perspiratory Function. The true function of perspiration is probably performed by the cell-structure of the sudoriferous follicles, and, like every other function, is capable of being excited or depressed by agents, calculated to act upon the peculiar susceptibilities of the tissue performing it. Certain diaphoretics have the property of stimulating the secreting tissue, and of thus increasing the secretion. it is not impossible that such a stimulation may be exercised sympathetically, by an impression first made on the mucous coat of the stomach or elsewhere, and thence transmitted through nervous centres to the skin. I do not know any medicine of which this mode of action can be predicated with certainty, or even great probability; but heat undoubtedly, I think, acts in this way. On this point more will be said directly.

The probability is, that all the diaphoretic medicines which act by stimulating the function, do so directly by contact with the secreting tissue, to which they are conveyed with the blood, after having been absorbed. There are certain medicines which appear to have a special tendency to operate upon the perspiratory function; or, to speak more precisely, to the influence of which this function is peculiarly or specially susceptible. These medicines are pre-eminently diaphoretic. There are others, which, in consequence of their irritant properties, cannot be tolerated in the circulation, and are thrown off indifferently by the emunctories intended to purify the blood, or by that one of them to which circumstances particularly direct their action. These medicines may be diaphoretic, diuretic, or purgative, according to the character of the influences with which they may be conjoined. They will often operate powerfully as diaphoretics, when aided by certain states of the system, and certain modes of administration. As the skin and kidneys are the chief emunctories for the elimination of absorbed and unacceptable matters in the blood, the substances just referred to usually escape through one of these routes, and, in doing so, stimulate the functions respectively, and consequently produce either diaphoresis or diuresis. But, as previously explained in the general observations on diuretics, there is a certain antagonism between these functions, through which it happens that, if one is promoted in excess, the other is proportionality diminished, and if one is diminished, the other is promoted. Consequently, medicines are seldom decidedly diaphoretic and diuretic at the same time. it has been before stated that cold has a tendency to suppress perspiration, and to direct action to the kidneys. The medicines now referred to will, therefore, prove diuretic when cold is made to cooperate with them. Heat, on the contrary, has the direct effect of determining to the surface. Hence they become diaphoretic when assisted by this agent.

There is, to a certain extent, a similar antagonism between the skin and the bowels. if the medicines now under consideration be given conjointly with cathartics, even though absorbed, they will often aid in the cathartic effect rather than operate either on the skin or kidneys; but, combined with opium, which restrains catharsis, while it stimulates the perspiratory function, they will prove powerfully diaphoretic, especially if assisted by warmth.

2. By Relaxing the Vessels of the Skin. There is certainly a great difference, at different times, in the vital cohesion or tone of the small blood-vessels, according to the varying influences to which they are exposed, which very much affects the amount and rapidity of the transpiration through them of the watery portion of the blood. With their healthy degree of tone or firmness, only such an amount of liquid escapes as is necessary to give due softness and lubricity to the tissues. When, however, they become feeble and relaxed, the watery parts of the blood pass through them with little resistance, and often in great abundance. Hence the copious night-sweats of debility, occurring when, in consequence of sleep, the organic functions are in their lowest state of activity. Hence, too, the cold sweats with which the body is often bathed in the last stage of vital prostration. Now, whatever agency, in the state of health, produces a similar relaxation of the cutaneous vessels, may occasion a similar transudation of liquid, and thus act as a diaphoretic. All nauseating substances have this property. Nothing is probably so relaxing to the surface as extreme nausea. Hence the nauseating emetics are all, in certain doses, diaphoretic. it is not, however, the proper secretory function, or the activity of the sudoriferous cells, which they promote; but only the exosmotic transpiration. Nevertheless, they are often equally efficient as remedies.