174 



THE SKELETON 



the ligamentum teres from the synovial cavity is connected. The opposite 

 extremities of the articular lunate surface which limit the acetabular notch are 

 united by the transverse ligament, and through the acetabular foramen thus 

 formed a nerve and vessels enter the joint. 



The obturator (thyreoid) foramen is sHuated between the ischium and pubis. 

 Its margins are thin, and serve for the attachment of the obturator membrane. 

 At the upper and posterior angle it is deeply grooved for the passage of the obtu- 

 rator vessels and nerve. 



Fig. 208. — The Pelvis of a Foetus at Birth, to show the Three Portions of the 



CoxAL Bones. 



The nucleus for the ilium 

 early in the second month 



The nucleus for the pubis appears 

 about the end of the fourth month 



The nucleus for the ischium appears 

 m the third month 



Blood-supply. — The chief vascular foramina of the coxal bone are found where the bone is 

 thickest. On the inner surface, the ilium receives twigs from the ilio-lumbar, deep circumflex 

 iliac, and obturator arteries, by foramina near the crest, in the iliac fossa, and below the terminal 

 line near the greater sciatic notch. On the outer surface the chief foramina are found below 

 the inferior gluteal line and the nutrient vessels are derived from the gluteal arteries. The 

 ischium receives nutrient vessels from the obturator, internal and external circumflex arteries, 

 and the largest foramina are situated between the acetabulum and the ischial tuberosity. The 

 pubis is supplied by twigs from the obturator, internal and external circumflex arteries, and 

 from the pubic branches of the common femoral artery. 



Fig. 209. — Coxal or Hip-bone, showing Secondary Centres. 



Appears at fifteen. Unites at twenty- 



Appears at fifteen. Unites at twenty. 



The lines of union are usually ob- 

 literated by the sixteenth year 



Appears at fifteen. Fuses at twenty 



Appears at fifteen. Fuses at twenty 



Ossification. — The cartilaginous rcsprcscntativc of the hi{)-bone consists of three distinct 

 portions, an iliac, an ischiatic, and a pubic i)ortion; the iliac and ischiatic portions first unite 

 and later the pubic portion, so that eventually there is found a single cartilaginous mass. Early 

 in the second month a centre of ossification ai)pears al)ove the acetabulum for the ilium. A 

 little later a second nucleus appears l)clow the cavity for the ischium, and this is followed in 

 the fourth month by a deposit in the pubic portion of the cartilage. At birth, the three nuclei 



I 



