EXCRETION. 439 



It serves to lubricate the hair and skin and prevent them from be- 

 coming dry and harsh. 



The surface of the fetus is generally covered with a thick layer of 

 sebaceous matter, the vernix caseosa, which possibly keeps 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. 



