138 



THE SKELETON 



Their 



Till- phalan.irts of tlic second row are shorter than those of the first row. 

 bases present two shallow pits, separated l)y a ridge. ^ , , . . 



The terminal, third, or ungual phalanges have an expanded shatt ior the sup- 

 ]iort of the nail. The hases are iileiitieal in shape with those of the second row. 



Ossification. Each i)halanx ossifies from two centres: one for the shaft, which 



is dcix.sitcd l.ctwccn the eighth and tenth weeks; and a nucleus for the epiphysis at 



Vm. l.")(l.— 0S.><IFIC ATIOX OF THE .MElAeARPALS AND PHAJ.AXUES. 



APPEARS IN THE THIRD YEAR. CONSOLI- 

 DATES IN THE TWENTIETH YEAR 



EPIPHYSIS FOR BASE 



METACARPAL OF THUMB 



EPIPHYSIS FOR HEAD 



APPEAR IN THE THIRD, AND CONSOLI- 

 DATE IN THE TWENTIETH YEAR 



I APPEAR BETWEEN THE THIRD AND FIFTH 

 [ YEAR. CONSOLIDATE IN THE EIGH- 

 TEENTH YEAR 



the })roxinial end, which appears between the third and fifth years. Consolidation 

 begins at the seventeenth, and is complete by the eighteenth year. 



The ossification of the terminal phalanx is peculiar. Like the other phalanges 

 it has a nucleus for the shaft and a secondary nucleus for the epiphysis; but the 

 centre for the shaft appears at the tip of the phalanx; whereas in the other pha- 

 langes the earthy matter is deposited in the middle of the shaft. 



TIIU If IP-BONE 



Till- liip-l)one (innominate bone) is of irregular shape, resembhng somewhat 

 the blade of a screw ]>ropeller. It consists of three parts, which, though separate 

 in early life, are, in the adult, firmly ankylosed. The three parts meet together at 

 the cotyloid cavity m- acetabulum. Tliey are named ilium, ischium, and 

 pubes. 



The ilium is Dh' upper exi>anded ])ortion; it articulates with the sacrum, and 

 forms the ui)per two-lifths of the acetabulum. The ischium is the lowest part of 

 the bone; it forms the ])()sterior and inferior two-fifths of the acetabulum, and 

 assists the pubes to form the obturator foramen. The pubes forms the anterior 

 fifth of the acetabulum, eomjdetes the obturator foramen, and stretches towards 

 the median line to meet with tlic opposite jtubes to form a symphysis. Each i)art 

 requires sej)arate consideration. 



