ACTION OF DIAPHORETICS. 523 



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 ; Anti- 

 mony; 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 com- 

 bination 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/cio, I make.) 



(b) Measures which diminish the amount of perspiration are 

 called anhidrotics (&v, priv., and ISpws, 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 termina- 

 tions 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. 



