THE SWEAT. 445 



sebaceous matter keeps the skin supple, and prevents the hair from becoming too 

 dry. Microscopically, the secretion is seen to contain innumerable fatty granules, 

 a few gland-cells filled with fat, visible after the addition of caustic soda, crystals 

 of cholesterin, and in some men a microscopic mite-like animal (Demodex folli- 

 culorum). 



Chemical Composition. The constituents are for the most part fatty; chiefly olein (fluid) 

 and palmitin (solid) fat, soaps, and some cholesterin ; a small amount of albumin and unknown 

 extractives. Amongst the inorganic constituents, the insoluble earthy phosphates are most 

 abundant ; while the alkaline chlorides and phosphates are less abundant. 



The vernix caseosa, which covers the skin of a new-born child, is a greasy mixture of seba- 

 ceous matter and macerated epidermal cells (containing 47 - 5 per cent. fat). A similar product 

 is the smegma prraputialis (52*8 per cent, fat), in which an ammonia soap is present. 



The cerumen or ear-wax is a mixture of the secretions of the ceruminous glands of the ear 

 (similar in structure to the sweat-glands) and the sebaceous glands of the auditory canal. Besides 

 the constituents of sebum, it contains yellow or brownish particles, a bitter yellow extractive 

 substance derived from the ceruminous glands, potash soaps, and a special fat. The secretion 

 of the Meibomian glands is sebum. 



[Lanoline. Liebreich finds in feathers, hairs, avooI, and keratin-tissues generally, a choles- 

 terin fat, which however is not a true fat, although it saponifies, but an ethereal compound of 

 -certain fatty acids with cholesterin. In commerce it is obtained from wool, and is known by 

 the above name; it forms an admirable basis for ointments, and it is very readily absorbed by 

 the skin.] Thus, the fat-like substance for protecting the epidermis is partly formed along 

 with keratin in the epidermis itself. 



3. The Sweat. The sweat is secreted in the coil of the sweat-glands. As long- 

 as the secretion is small in amount, the water secreted is evaporated at once from 

 the skin along with the volatile constituents of sweat ; as soon, however, as the 

 secretion is increased, or evaporation is prevented, drops of sweat appear on the 

 surface of the skin. The former is called insensible perspiration, and the latter 

 sensible perspiration. [Broadly, the quantity is about 2 lbs. in twenty-four 

 hours.] 



The sensible perspiration varies greatly; as a rule, the right side of the body perspires more 

 freely than the left. The palms of the hands secrete most, then follow the soles of the feet, 

 cheek, breast, upper arm, and fore-arm (Peiper). It falls from morning to mid-day, and rises 

 again towards evening, reaching its maximum before midnight. Much moisture and cold in 

 the surrounding atmosphere diminish it, and so does diuresis. In children, the insensible per- 

 spiration is relatively great. The drinking of water favours it, alcohol diminishes it {H. Schmid). 



Method. Sweat is obtained from a man by placing him in a metallic vessel in a warm bath ; 

 the sweat is rapidly secreted and collected in the vessel. In this way Favre collected 2560 

 grammes of sweat in 1 hour. An arm may be inclosed in a cylindrical vessel, which is fixed 

 air-tight round the arm with an elastic bandage (Schottin). 



Amongst animals, the horse sweats, so does the ox, but to a less extent ; the vola and planta 

 of apes, cats, and the hedgehog secrete sweat ; the snout of the pig sweats (?), while the goat, 

 rabbit, rat, mouse, and dog are said not to sweat (Luchsingcr). [The skin over the body and 

 the pad on the dog's foot contain numerous sweat-glands, which open free on the surface of the 

 pad and into the hair-follicles on the general surface of the skin ( TV. Stirling).'] 



Microscopically. The sweat contains only a few epidermal scales accidentally mixed with it, 

 and fine fatty granules from the sebaceous glands. 



Chemical Composition. Its reaction is alkaline, although it frequently is acid, 

 owing to the admixture of fatty acids from decomposed sebum. During profuse 

 secretion it becomes neutral, and lastly alkaline again (Triimpy and Luchsinger). 

 The sweat is colourless, slightly turbid, of a saltish taste, and has a characteristic 

 odour varying in different parts of the body ; the odour is due to the presence of 

 volatile fatty acids. The constituents are waMr, which is increased by copious 

 draughts of that fluid, and solids, which amount to T180 per cent. (0'70 to 2*66 per 

 cent. Funke), and of these 0*96 per cent, is organic and 0*33 inorganic. Amongst 

 the organic constituents are neutral fats (palmitin, stearin), also present in the 

 sweat of the palm of the hand, which contains no sebaceous glands, cholesterin, 

 volatile fatty acids (chiefly formic, acetic, butyric, propionic, caproic, capric acids), 

 varying qualitatively and quantitatively in different parts of the body. These 

 acids are most abundant in the sweat first (acid) secreted. There are also traces 



