When, under the conditions referred to at the commencement of this article, the sur face becomes covered with sweat, the various matters passing away from the skin by exces sive secretion have been examined by che mists with the following results : The total solid matters passing away from the unexcited skin have been calculated at about 7 to 8 scruples in the 24 hours, but the very nature of the inquiry prevents any great reliance being placed in such results.
When sweat is collected, as was done by Simon, from persons subjected to the vapour bath, it appears as a turbid fluid, yielding a deposit by standing. This deposit consists of epithelium scales. The clear fluid was found by Simon to possess a specific gravity of 1003 to 1004. This result, however, must be modified continually by the water condensed on the surface from the aqueous vapour of the bath. The fluid was acid, but only very slightly so, and in the course of twenty-four hours it became neutral. The acidity of the sweat was therefore dependent on the pre sence of carbonic acid. Ammonia was evolved from it after exposure. Simon analysed his own sweat. He found it to develop an odour of ammonia, and could detect that gas by testing with the vapour of hydrochloric acid. On evaporation, the peculiar smell of animal extractive matter was observed. When the dry matter was triturated with potash, ammo nia came off. Sulphuric acid added to ano ther portion developed sulphurous acid at first, and afterwards produced a strong odour of acetic acid. In one instance observed by Simon, the sweat gave off the odour of butyric acid so strongly as to leave no doubt on his mind of the presence of that substance. From various experiments, Simon concludes normal sweat to contain 1. Matters soluble in ether : traces of fat, sometimes including butyric acid.
2. Matters soluble in alcohol: alcoholic extractive, free lactic or acetic acid, chloride of sodium, lactates and acetates of potash and soda, lactate or hydrochlorate of ammonia.
3. Matter soluble in water : aqueous ex tractive, phosphate of soda, and, occasionally, alkaline sulphate.
4. Matters insoluble in water : desqua mated epithelium, phosphate of lime, and peroxide of iron.
Berzelius examined and analysed sweat as obtained from the forehead. He found it to contain much the same substances that exist in the acid juice of flesh. He states chloride of sodium to be in excess, however. The
skin is certainly an active excreter of free phosphoric and lactic acids, and assists the urine in its important office of discharging these acids from the system. Landerer has lately shown the presence of urea in healthy sweat, and it is probably by decomposition of this substance that collected sweat becomes ammoniacal. Thus, the skin would appear, under varying conditions, to assume the excre tory duties of the lungs and kidneys, and we are almost constrained to regard its function as supplementary as well as complimentary to that of respiration and the excretion of urine.
Anselmino has, perhaps, made the best analyses of the sweat. According to him one hundred parts of the solid matters of sweat contain l. Substances insoluble in water and alcohol (chiefly calcareous salts) 2.0 2. Aqueous extractive matter (re garded as salivary matter by An selmino, according to Berzelius without sufficient reason), and sulphates - - - - 21.0 3. Spirituous extractive (chloride of sodium and osmazome) - - 4. Alcoholic extractive (osmazome, lactic acid and its salts, regarded by Anselmino as acetic acid and acetates) - - - - 20.0 In order to obtain the solid matters of the sweat, Anselmino collected it in the vapour bath by means of clean sponges. The fluid so obtained was filtered, and the water dis tilled off: Acetate of ammonia was found in the receiver. Simon considers acetic acid to be a constant constituent of the sweat, and with Berzelius considers hydrochlorate of am monia to be a normal component of the fluid. Simon, though agreeing in the general with the results of Anselmino, failed to detect sulphates in freshly collected sweat. He found it, however, in the incinerated residue, from which he infers that some of the con stituents of sweat contain sulphur.
The following is Anselmino's analysis of sweat in 1000 parts :— Water - - - 995.00 987.500 Epidermis and calca reous salts - - '10 •250 Aqueous extractive matter (sulphates) 1•05 2'625 Spirituous extractive, chlorides of sodium and potassium - 2'40 6.000 Alcoholic extractive, acetates,lactates,and free acetic acid - 1.45 3.625 In the ash of the dried residue of sweat, Anselmino found carbonate, sulphate, and phosphate of soda, chloride of sodium, phos phate and carbonate of lime, with traces of iron. In every 100 parts of dry matter of sweat, he found [22.9 of these fixed saline matters.