SWEAT (A. S. swat, Sansc. svaidas, Lat. sudor; Gr. hydor, moisture; Let. ud(us) = wet), or perspiration. The nature, composition, and uses of this fluid in the normal state have been sufficiently noticed in the article SKLN. It may be additionally remarked, in connection with the physiology of sweat, that the composition of this fluid varies mate rially according to the part of the body from which it is secreted. Thus Funk found the sweat of the feet was richer in fixed salts than that of the arm, in the ratio of 3 to 3; and Schotten found a considerable preponderance of potassium in the former. Iu the negro, Dr. Copland and other observers have found that both the gaseous exhalations from the skin, and the solid matters contained in the sweat, were much greater than in the white races. It has been shown in the article SKIN that the sweat-glands, like the lungs and kidneys, act as depurating organs, and separate and carry off effete matters from the blood. This eliminating action of the skin is modified in various diseases; in some cases being diminished, as in the early stage of fevers, in inflammations before suppuration commences, in scurvy, diabetes, sunstroke, etc., while it is more or less in creased in the sweating stage of ague, in acute rheumatism, in Asiatic cholera, in certain adynamic fevers, in the advanced stages of pulmonary consumption, in the formation of matter in internal parts, etc. The sweat is naturally acid in health, but in prolonged sweating the secretion becomes neutral, and finally alkaline. Little is known with cer
tainty regarding the coloring matters of sweat. In cases of jaundice, the sweat some times communicates a yellow tinge to the body-linen; and instances of blue, red, and bloody sweat are on record. Cases of sweat of these colors are recorded in Simon'a Animal Chemistry (Syd. Soc. Trans.), (London, 1845), vol. ii., p. 110. Cases of unilateral sweating, stopping abruptly at the middle line, have been occasionally noticed, espe cially in aneurism of the aorta.—See Gairdner's Clinical Medicine, page 557. Dr. Devitt has pointed out the use of hot water as a remedy for profuse perspiration. He has found it serviceable in (1) oversweating in good health and hot weather; (2) undue sweating in special parts of the body, as the hands, feet, or armpits ;(3) true hectic; and (4) ordinary night sweats in phthisis not preceded by hectic symptoms. To be of any service, the water must be applied at as great a heat as the" patient can possibly bear (see his paper on this subject in the Ifecheal Times for March 4, 1865). For a very interesting and learned discussion on our Saviour's bloody sweat during his passion, the reader may con sult Stroud On the Physical Cause of the Death of Christ, and Trusen's chapter Von. dem Blutschweisse Christ in his Darstellung der Biblischen .Krankheiten,1843.