FUNCTIONS OF THE SKIN 91 



the sweat glands, can relieve the overburdened kidneys, 

 a fact which is taken advantage of to induce sweating, 

 by drugs or other means, when the kidneys do not prop- 

 erly perform their function, as in the condition of ec- 

 lampsia which sometimes endangers a woman in child- 

 bearing. 



Nerve Control. There is reason to conclude that there 

 is a sweat center, probably, in the medulla and perhaps 

 subsidiary centers in the cord. Secretory fibers are car- 

 ried directly to the glands and are ordinarily excited by 

 high temperature, which acts reflexly through the cen- 

 tral nervous system. Heat alone will not cause sweat- 

 ing. In the high temperatures of fever, sweating is 

 notably absent, while ' present in profuse degree in the 

 pale skin of the terror stricken. This proves, also, that 

 an increase in the amount of blood in the skin is not 

 enough to cause sweat, and that a decrease does not 

 prevent its secretion. Many drugs, like pilocarpin will 

 increase the activity of the sweat glands and some, like 

 atropin will paralyze the secretory fibers. 



Sebaceous Glands .These simple or compound alve- 

 olar glands are usually found associated with the hairs, 

 when their ducts open directly into the hair, follicles. 

 The cells which line them are cast off apparently as a 

 part of the secretion of the glands, sebum, which is an 

 oily semiliquid which sets into a cheesy mass, such as 

 can be squeezed from the pimples or comedones, which 

 disfigure many people when the ducts become stopped. 

 The secretion of those glands located in the ear, when 

 mixed with that of other glands, forms ear wax. The 

 secretion of the sebaceous glands probably forms an 

 oily coating for the SKin and hairs which protects the 

 former by preventing too rapid evaporation and keeps 

 the latter from becoming too dry and brittle. 



