THE SKIN 327 



Sebum is the oily fluid secreted by the sebaceous 

 glands. It contains, by analysis^ water, epithelium, 

 proteins, fats, cholesterin, and inorganic salts. 



The pouring-out of seburn by the glands is not a 

 true secretion, but occurs as a result of multiplication 

 and breaking down of the gland epithelium. Sebum 

 when first secreted is oily and semiliquid, but soon 

 becomes hard and acquires a cheese-like consistency. 

 It lubricates the hair and skin and prevents dryness 

 and roughness. 



Vemix caseosa is the whitish, oily substance seen 

 covering the body of the newborn child. It is supposed 

 to keep the skin in a normal condition by protecting 

 it from the effects of the long-continued action of the 

 amniotic fluid in which the fetus is suspended during 

 intra-uterine development. 



The Sweat Glands. The sweat glands are the glands 

 which when active promote perspiration and aid in 

 heat dissipation, at the same time eliminating waste 

 products as the result of body metabolism, brought to 

 them by the blood. 



They are situated in the lower part of the corium, 

 derma, or true skin, and sometimes in the subcutaneous 

 tissue. The glands are tubular, and the lower or 

 inner extremity is coiled upon itself a number of 

 times, forming a rounded mass. Extending from 

 this coil to the epidermis is the duct which follows 

 a straight course in this situation, and after a few 

 spiral turns, opens onto the surface of the skin. The 

 glands consist of epithelial cells which rest upon a 

 very thin basement membrane. These glands are 

 very numerous; it has been estimated that they 

 average from 2,000,000 to 2,500,000. They are more 

 abundant in some localities than others. Each sweat 

 gland is richly supplied with bloodvessels and nerves 

 (vasomotor and secretor). 



Perspiration. Perspiration or sweat is the fluid 

 secreted by the sweat glands of the skin. It is a 



