Celsus treats of the methods for producing free perspiration with more than his usual minuteness. Sweating, he says, may be produced either by dry heat or by baths. The modes of applying dry heat, which he mentions, are by heated sand, the laconicum or sweating apartment of the ancient bath (see Sect. LI), the clibanus or moveable furnace, and the vapour-baths of Baiæ. To these he adds strong exercise. He also treats minutely of the application of baths and fomentations for the cure of diseases, (ii, 17.) Consult Stobæus (100.) Haly Abbas directs us to restore the perspiration, when stopped, by exercise, friction, baths, and the affusion of hot water over the body. He further recommends friction with the oil of violets, and such things as are mentioned by our author. (Pract. i, 12.) Rhases recommends internally, castor, opoponax, or opium mixed with honey, and given in tepid water. Externally, he recommends friction, with the oil of chamomile, of pellitory, or the like. (Contin. 31.) Mesue mentions fumigations with calamint, cinquefoil, carpobalsam, and bdellium. Albengnefit recommends the same, and also friction with calefacient oils, and the internal administration of cumin, calamint, and the like. The ancients, as Prosper Alpinus remarks, seem to have trusted more in external than in internal means for producing free perspiration. They were aware that when the system is greatly over-heated, a draught of cold water, by reducing the temperature of the body, may prove sudorific. This fact is distinctly stated by Galen; and, in accordance with this principle, Rhases prescribes cold water in the hot stage of the smallpox, to facilitate the eruption of the pustules. On the sudatoria or vapour-baths of the ancients, see Baccius (de Thermis, iv), and Sect. LI, below. Horace thus alludes to the vapour-baths at Baiæ: “Sane myrteta relinqui, Dictaque cessantem nervis elidere morbum Sulphura contemni vicus gemit.” (Epist. i, 15.) Upon which Sanadon remarks: “By _sulphura_, the poet means the stoves, where sulphureous vapours exhaling from the earth cause a dry heat, which provokes sweat.” Among the artificial means used by the ancients for procuring perspiration, we may here mention the sand-bath, as it was called, which consisted in rolling the body in sand heated by the sun. (Cælius Aurel. Tard. Pass, iii, 4; Avicenna, i, 2, 2, 20.) Strong friction in the sun was also used as a means for producing perspiration. See, in particular, Avicenna (i, 2, 2, 20.) SECT. XLIX.—ON AIRS.