THE HUMAN SKELETON 
47 
crest, and the two ventral, and two dorsal spines; posterior to 
the latter the greater sciatic notch, in the middle of which the 
ilium joins the ischium; the auricular surface on the medial surface 
of the bone for the articulation with the sacrum. 
The os ischii is the most posterior component, having the 
form of a loop. Note the sciatic tuber, which supports the weight 
of the body in sitting; the sciatic spine, separating the greater 
from the lesser sciatic notch; the ramus, meeting the ramus of the 
pubis and bounding the obturator foramen. 
The os pubis is the most ventrally situated component. Note 
the body forming, with the corresponding portion of the other 
side, the pubic arch; the symphyseal surface along which it comes 
in contact with the pubic bone of the other side, in the midventral 
line; the ramus, meeting the ramus of the ischium. 
Sex Differences Shown by the Pelvic Girdle. —These are best 
seen when the two ossa coxae and the corresponding sacrum are 
fitted together and held firmly in place. Compare as large a 
number of examples as possible as to the subpubic angle formed by 
the posterior margins of the pubic rami, narrow (averaging 58°) 
in the male, wide (averaging 76°) in the female; shape of the iliac 
fossa, obturator foramen, sacro-sciatic notch, and sciatic tubers; 
the presence or absence of a preauricular fossa, which most females 
possess; and the shape and size of the ring formed by the sacrum 
and the ossa coxae. In correctly mounted male and female 
skeletons note the difference in the inclination of the pelvis as a 
whole to the axis of the trunk. (Cf. the pelvic girdle with that of 
quadrupedal forms in this particular and in general proportions.) 
(, b ) The Free Limb. 
Femur (the longest bone of the body, the entire height = 
3.7 X length of femur). —Note head with its surface for articu¬ 
lation with the acetabulum; pit (fovea) in the middle of the head 
for the ligamentum teres which holds the femur in the acetabulum; 
anatomical neck (coincides with the surgical neck); note variation 
of the angle between the neck and the shaft at different ages, with 
nearer approach to a right angle and consequent liability to 
fracture in old age; greater and lesser trochanters connected by 
intertrochanteric lines; trochanteric fossa; linea aspera; popliteal 
