3. The Sweat-glands: Diaphoretics, Sudorifics, Anhidrotics.-The function of perspiration is under our control in almost every portion of its complex mechanism.

a. Measures which increase the amount of perspiration are called diaphoretics or sudorifics. The afferent thermic nerves in the skin can be readily stimulated by means of heat, as described in chapter xv (. Therapeutical Processes Connected With The Surface Of The Body)., whether by moist heat in the form of the warm water- or vapour-bath, or various kinds of pack; by dry heat, as in the Turkish bath; or by general warmth of the air, of the room, or of the clothing. The familiar effect of Alcohol in inducing perspiration appears to be chiefly produced in the same way. Other afferent nerves may be used to stimulate the sweat-centres reflexly, such as those of the mouth throat, and stomach by hot spiced drinks. Perspiration may be induced by acting on the perspiratory centre directly. This may be accomplished by measures which increase the venosity of the blood, such as narcotics, including Opium, Chloral, Chloroform, Ether, and Alcohol in the later stages of their action; by Nicotin (Tobacco), by Pilocarpin (Jaborandi) in part; and by all measures which increase the flow of warm blood through the sweat-centres, such as hot drinks. The efferent nerve-trunks of perspiration may be stimulated by electricity, but this method is not therapeutically employed. The terminations of the nerves in the sweat-glands and the secreting cells can be powerfully stimulated by Pilocarpin, which causes an exceedingly profuse and rapid flow of sweat. Diaphoresis will be favoured by a free supply of blood to the glands, i.e. by dilating the vessels, as just described. A number of substances induce diaphoresis without their mode of action being clearly understood, such as- Citrate of Ammonia, and especially Acetate of Ammonia, which possibly stimulate the secreting cells, and are excreted by them along with an increased amount of water, as we see in the kidney; Antimony; some or all of the aromatic substances in a degree, especially Camphor; and several empirical remedies, viz. Ser-pentary, Sassafras, Sarsaparilla, Guaiacum, Mezereon, and Senega.

It will be observed that several of our powerful diaphoretics act on more than one part of the perspiratory mechanism. Thus Alcohol dilates the cutaneous vessels, increases the rate of blood-flow through the skin, and stimulates both the afferent nerves and the centres of perspiration. Warm applications to the skin and hot drinks also influence both the circulatory and the perspiratory part of the refrigerating function; and by a combination of these and other means we may produce a very powerful effect. When this is the result, and the sweat flows abundantly from the surface, the measures and result are said to be sudorific {sudor, sweat, and facio, I make.)

(b) Measures which diminish the amount of perspiration are called anhidrotics (The Body Heat And Its Regulation The Skin Part 2 18 priv., and The Body Heat And Its Regulation The Skin Part 2 19 sweat.) Some of these act upon the afferent nerves, especially moderate local cold, obtained by fanning, light clothing, and a cool atmosphere generally; and sponging with cool, tepid, or even hot water. Others depress the perspiratory centre-possibly in part directly, certainly indirectly by strengthening the heart and respiration, and thus reducing the venosity of the blood which powerfully stimulates it. Such are food, which is one of the best means of preventing the "cold sweats," of exhausting diseases, Alcohol, Ammonia, Strychnia, Iron, and fresh air or good ventilation. The efferent sweat-nerves may possibly be depressed by Opium, which in certain combinations, e.g. with Diluted Sulphuric Acid, is an anhidrotic, acting either in this or some unknown way. By far the most powerful anhidrotic drugs act upon the terminations of the perspiratory nerves in the glands, namely, Atropia and Hyoscyamia. The effect of these alkaloids or of the Extract of Belladonna is very marked. Measures which contract the blood-vessels of the glands, will pro tanto be anhidrotic also. Such are - sponging with solutions of Sulphuric Acid and Water, or of Tannin, which constringe the parts, and Oxide of Zinc, given internally.

Lastly, the modus operandi of certain anhidrotics is still doubtful, and their employment so far empirical, e.g. Zinc, Quinia, and Opium under particular circumstances. It is possible, however, that these and other measures control the pathological cause of the sweats, in a manner to be afterwards indicated.

4. Other Channels Of Loss Of Heat

Other Channels Of Loss Of Heat. The kidneys and the bowels afford us a direct means of reducing the temperature of the body by the abstraction of an increased amount of warm excretions, in the form of urine and watery motions. In the case of the bowels the effect is decidedly assisted by the reflex dilatation of the cutaneous vessels which accompanies purgation, as described in chapter vi (The Intestine).

5. The Heat-Forming Tissues

The Heat-Forming Tissues. In discussing metabolism in chapter ix., we found that we possess the power of diminishing tissue change, and the production of heat, by various means. Here we shall refer only to certain drugs which possess this action. We call these antipyretics (The Body Heat And Its Regulation The Skin Part 2 20 against,

The Body Heat And Its Regulation The Skin Part 2 21 fever). The most powerful of these is Cinchona (Quinia), which interferes with metabolism generally, lessens the amount of heat produced, diminishes the excretions, and spares the organs. Salicin and Salicylic Acid, Resorcin, Chinolin, and Kairin, have a similar but less powerful action. Whilst these drugs distinctly reduce or spare the activity of the tissues, they have but little influence in reducing the temperature of healthy individuals, this effect probably being prevented by the ordinary mechanisms of regulation. Alcohol also diminishes tissue waste, apparently in a different way from Quinia, viz. by being itself decomposed in the tissues with great readiness, thus sparing the organs. Even an increased amount of heat is generated in the tissues by the oxydation of Alcohol, but so greatly does it stimulate refrigeration, as we have seen, that its total effect on the organism is antipyretic. The Aromatic substances have a less powerful influence in diminishing metabolism. Possibly, Digitalis, Aconite, and Veratria, have also an antipyretic effect, like Alcohol, but their mode of action is obscure, unless it occur entirely through the circulation, as has been already suggested.