896 



THE EXTERNAL SECRETIONS 



lips. Their number has been estimated at two millions^ and their 

 total secretory surface at 1080 m^ The cells lining the coiled up 

 extremity of these glands are columnar in shape and possess a gran- 

 ular cytoplasm. Externally they border upon a dense network of 

 capillaries. 



The sweat is a clear, colorless liquid of low specific gravity (1.004). It consists 

 of 982 parts of water per 1000 c.c; and contains small quantities of salts, neutral 

 fats, volatile fatty acids, and traces of proteins and urea. The inorganic salts include 



sodium chlorid and small quantities of alkaline 

 sulphates and phosphates. The latter impart 

 to it a faint alkaline reaction, although when first 

 secreted it is prone to be acid, owing to the pres- 

 ence of a slight amount of sebaceous material. 

 Profuse sweating, however, may yield other pro- 

 teins, such as uric acid, creatinin, ethereal sul- 

 phates, phenol, skatol, and albumin. ^ Conse- 

 quently, sweating is called for whenever the 

 activity of the kidneys is temporarily suppressed. 

 Muscular exercise also tends to augment the urea 

 content of the sweat, and in addition, gives rise 

 to an elimination of CO2 which may amount to 

 as much ^s 20 grams per day. Under normal 

 conditions, however, the secretion of sweat serves 

 merely as a means of eliminating water and not 

 of solid excrements. While this fact may be re- 

 garded as sufficient reason to classify sweat as an 

 excretion, the use made of it subsequently in 

 moistening the surface of the body and in regulat- 

 ing the body-temperature, may prompt us to con- 

 sider it as a secretion. 



The small quantity of sweat generally 

 produced, evaporates and leaves non-vola- 

 tile constituents upon the skin,^ but 

 naturally, its total quantity differs greatly 

 with the general condition of the body 

 and the surroundings. A person dressed 

 moderately warm may secrete as much 

 as 2 or 3 liters in a day, although an out- 

 side temperature which causes the tem- 

 perature of the skin to rise above 33°C., 

 yields a much larger quantity. A part 

 of this may be removed by evaporation, 

 while the remainder forming the so-called visible sweat, is absorbed by 

 the clothing or is lost in mass. Naturally, a moisture-laden atmos- 

 phere retards the evaporation and tends to produce a much larger 

 quantity of visible sweat than a dry and warm atmosphere. It should 

 also be remembered that the secretion of sweat is closely correlated 

 with that of urine, because copious sweating most generally diminishes 



1 Krause, Handb. der Anatomic, 1879. 



2 Brieger and Dieselhorst, Deutsch. med. Wochenschr., xxx, 1904, 161. 

 « Schierbeck, Archiv fiir Anat. und Physiol., 1893, 116. 



Fig. 488. — Diagrammatic 

 Representation of the Skin, 

 Showing the Location of the 

 Sweat Glands. 



H, Horny layer; L, stratum 

 lucidum; M, Malpighian layer; 

 P, corpuscles of Paccini; PL, 

 papillae of the cutis vera; C, 

 cutis vera; S, sweat gland; SC, 

 subcutaneous tissue. 



