SKELETON AND LIMBS. 643 



abdomen, and terminates in a pointed extremity. Subsequently the 

 pelvis and the muscular parts seated upon it grow so much faster 

 than the sacrum and coccyx, that the latter become concealed 

 under the adjoining soft parts, and the rudimentary tail accord- 

 ingly disappears. 



The integument of the embryo is at first thin, vascular, and ex- 

 ceedingly transparent. It afterward becomes thicker, more opaque, 

 and whitish in color ; though even at birth it is more vascular than 

 in the adult condition, and the ruddy color of its abundant capil- 

 lary vessels is then very strongly marked. The hairs begin to 

 appear about the middle of intra-uterine life ; showing themselves 

 first upon the eyebrows, and afterward upon the scalp, trunk and 

 extremities. The nails are in process of formation from the third 

 to the fifth month ; and, according to Kolliker, are still covered 

 with a layer of epidermis until after the latter period. The seba- 

 ceous matter of the cutaneous glandules accumulates upon the skin 

 after the sixth month, and forms a whitish, semisolid, oleaginous 

 layer, termed the vernix caseosa, which is most abundant in the 

 flexures of the joints, between the folds of the integument, behind 

 the ears and upon the scalp. 



The cells of the epidermis are repeatedly exfoliated after the first 

 five months of foetal life (Kolliker), and replaced by others of new 

 formation and of larger size. These exfoliated epidermic cells are 

 found mingled with the sebaceous matter of the vernix caseosa in 

 great abundance. This semi-oleaginous layer, with which the in- 

 tegument is covered, becomes exceedingly useful in the process of 

 parturition, by lubricating the surface of the body, and allowing it 

 to pass easily through the generative passages. 



