534 CUTANEOUS RESPIRATION. CUTANEOUS SECRETION. 



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

 of cutaneous fat and macerated epidermis. It contains 35 per cent, of water 

 and 14 per cent, of ethereal extracts, together with traces of albumin, chlorin, 

 calcium, magnesium, and phosphoric acid. Examination for fats disclosed the 

 presence of cholesterin, isocholesterin, oleic and palmitic acids (salts of fatty acids) , 

 together with glycerin. The preputial smegma (52.8 per cent, fat) is a similar 

 product, in which an ammonium-soap occurs. Ear-wax is a mixture of the secre- 

 tion of the ceruminous glands, which resemble the sudoriferous glands, and of 

 the glands of the hair-follicles of the auditory canal. It contains, in addition to 

 the constituents of the cutaneous fat, a brown pigment, soluble in alcohol and 

 fat; a bitter yellow extractive ; albumin; lecithin; cholesterin; potassium-soaps; 

 and a special fat. The secretion of the Meibomian glands is cutaneous fat. The 

 production of the fatty coating necessary for the oiling of the epidermis takes 

 place, together with the formation of keratin, in part within the epidermis itself. 

 The presence of cholesterin-fats in this situation has also been demonstrated in 

 the layer of beginning cornification. 



The sweat is secreted by the convoluted glands, the nuclei of the 

 secretory cells acquiring a more nearly circular outline, and the cells, in 

 the horse, becoming granular. So long as the secretion is confined with- 

 in narrow limits, the water secreted, together with the volatile constitu- 

 ents, evaporates at once from the surface of the skin. As soon, however, 

 as the secretion increases or evaporation is inhibited, the sweat appears 

 in pearly drops at the orifices of the sweat-glands. The former has been 

 designated insensible, the latter sensible perspiration. 



The insensible perspiration varies widely. Generally, the right side of the 

 body perspires more freely than the left. The palm of the hand sweats in greatest 

 measure. Then, in order, follow the sole of the foot, the cheek, the breast, the 

 thigh, and the forearm. Sweating increases slowly from the morning onward, in 

 greater degree in the afternoon, and declines after the evening meal; then, 

 increasing, it reaches its maximum before midnight. The presence of a large 

 amount of moisture in the surrounding air diminishes the perspiration, as do also 

 copious sweating previously and increased diuresis. Children have a relatively 

 greater insensible perspiration. Ingestion of water increases, and withholding of 

 water diminishes, the sweat; alcohol also diminishes it. The smallest measure of 

 dissipation of watery vapor takes place at 15 C., while both above and below 

 this temperature-level the dissipation increases. The ordinary temperature be- 

 neath the clothing is about 32 C. At this temperature the insensible perspiration 

 equals 1500 grams of water. When the temperature of the surrounding atmos- 

 phere is 33 C. and above, sweating begins. Generous nutrition, warm clothing, 

 and work cause greater excretion of water. 



Pathological. The insensible perspiration is increased in the presence of dis- 

 eases of the skin, principally the acute erythemata. It is diminished in cases of 

 scarlet fever, especially in association with uremia. 



Sweat can be collected in largest amount from human beings by exposure 

 in the steam-bath at a high temperature in a metallic tub in which the subject 

 lies and into which the secretion of the skin flows. In this way Favre collected 

 2560 grams of sweat in one and a half hours. It is convenient, also, to obtain 

 thus the partial secretion of sweat from the arm, which is placed in a glass cylinder 

 hermetically sealed by rubber bandages about the arm. 



In animals, sweating takes place in the horse, less in cattle, on the palm and 

 the sole of the foot of the ape, the cat, the hedgehog. Swine sweat (?) on the 

 snout, cattle about the mouth (?), while goats, rabbits, rats, mice, and dogs do 

 not sweat at all. 



Microscopically, sweat contains epidermal scales and fatty granules 

 from the glands of the skin accidentally present. The sweat is colorless 

 and slightly turbid, with a specific gravity of 1005. It has a salty taste 

 and a characteristic odor in different portions of the body, due to 

 volatile fatty acids. 



The moist epidermis, including the hair and the nails, has an acid 

 reaction, while the cutis has an alkaline reaction. The sweat secreted 



