118 



EOXES OF THE LOWER LIMB. 



uhole lengtli, the cuboid boue, and the fourth and fifth toes, a great 

 part of which rests npon the ground in standing. Besides bein^ 

 arched longitudinally, the foot presents likewise a transverse arch 

 formed behind by the cuboid and three cuneiloriu bones, and in front 

 by the metatarsal bones. 



OSSIFICATION OF THE BONES OP THE PELVIS AND LOWER LIMB. 



Os innominatura. — The innominate bone is fonned from the three principal 

 pieces previously mentioned, viz., the ilium, ischium, and os pubis, and from 

 various others of an epiphysial nature. Ossification commences in the cartilage 

 of the ilium a little later than in other large bones, bone lieginning to be depo- 

 sited above the sciatic notch in the 8th or !)th week. This is followed by similar 

 deposits in the thick part of the ischium below the acetalnilum in the 3rd 

 month, and in the ascending ramus of the pubis in the ith or 5th month. At 



Fig. 105. 



Fig. 105. — Ossification op the Os I.nnominatu.m (R. Quain). 



A, the condition of the bone at birth. Bone has spread from tliree nuclei into the 

 ilium, ischium, .and pubis, which meet in the cartilage of the acetabulum. 



B, from a child under six years of age. The rami of the ischium and pubis are farther 

 ossified, but still separate. 



C, a bone of two or three .years later, in which the rami ai'e united. 



D, the bone of the right side from a person of about twenty years. Union has taken 

 place in the acetabulum, and the additional epiphyses are seen in the crest of the ilium, 

 the anterior inferior spine, the ischial tuberosity, and the margin of the symphysis pubis. 



In A, B and C, 1, ilium ; 2, ischium ; 3, pvihis ; below D, 4, separated Y-shaped piece 

 formed of several fragments which begin to ossify about the 14th year, and often unite 

 into this form before the completion of the acetabulum ; 5, epiphysis of the crest ; 6, that 

 of the tuberosity of the ischium ; 7, that of the symphysis ijubis ; 8, that of the anterior 

 inferior spine of the ilium. 



birth the gi-eater part of the acetabulum, the crest of the ilium, the tuberosity 

 and ramus of the ischium, the body and descending ramus of the pubis are still 

 cartilaginous ; ossification, however, from the three primary centres has extended 

 into the mai-gin of the acetabulum. In the 7th or Sth year the rami of the ischium 

 and pubis become completely united by bone. The parts which meet in the 

 acetabulum are still se]iarated by a tri-radiate strip of cartilage, which from 

 its shape has been called the Y cartilage. Tliis cartilage begins to be ossified 

 from one or more centres about the age of iniberty, and the intermediate bone 

 or epiphysis so formed is united to the neighbouring parts about the 17th or 

 18th year. Epiphyses are likewise formed in the cartilage of the crest of the 



