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THE LOWER LIMB. 207 
SESAMOID BONES. 
Two little oval nodules (ossa sesamoidea), which play in grooves on the palmar 
aspect of the articular surface of the head of the first metacarpal bone, are constantly 
met with in the tendons and hegaments of that metacarpo-phalangeal articulation. 
Similar nodules, though of smaller size, are sometimes formed in the corresponding 
joints of the other fingers, more particularly the index and little finger ; as Thilenius 
has pointed out ( Morph. Ar beiten, vol. v.), these are but the persistence of cartilaginous 
elements which have a phylogenetic interest. 
THE LOWER LIMB. 
THE PELVIC GIRDLE AND THE LOWER EXTREMITY. 
The pelvic girdle is formed by the articulation of the two haunch bones with 
the sacrum behind, and their union with each other in front, at the joint called the 
symphysis pubis. 
THE INNOMINATE BONE. 
The innominate or haunch bone (0s coxe) is the largest of the flat bones of the 
skeleton. It consists of three parts-—the ilium, the ischium, and the pubis— 
primarily distinct, but fused together in the process of growth to form one large 
irregular bone. The coalescence of these elements takes place in and around the 
acetabulum, a large circular articular hollow which is placed on the outer side of the 
bone. The expanded wing-like part above this is the ilium; the stout V-shaped 
portion below and behind it constitutes the ischium ; while the >-shaped part to 
the inner side, and in front and below, forms the pubis. The two latter portions of 
the bone enclose between them a large aperture of irregular outline, called the 
thyroid or obturator foramen (foramen ‘obturatorum), which is placed in front and 
below, and to the inner side of the acetabulum. 
The ilium, almost a quadrant in form, consists of an expanded plate of bone, 
having a curved superior border, the iliac crest (crista iliaca). Viewed from the 
side, this forms a curve corresponding to the circumference of the circle of which 
the bone is the quadrant ; viewed from above, however, it will be seen to display 
a double bend—convex anteriorly and externally, and concave posteriorly and 
externally. The iliac crest is stout and thick, and for descriptive purposes it is 
divided into an outer lip (labium externum), an inner lip (labium internum), and 
an intermediate surface (linea intermedia) which is broad behind, narrowest about 
its middle, and wider again in front. About 24 inches from the anterior extremity 
of the crest the outer lip is usually markedly prominent and forms a projecting 
tubercle, which can readily be felt in the living. Attached to these surfaces and 
lips anteriorly are the muscles of the flank, “whilst from them posteriorly the 
latissimus dorsi, quadratus lumborum, and erector spine muscles derive their 
origins. In front, the crest ends ina pointed process, the anterior superior iliac spine 
(spina iliaca anterior superior). To this the outer extremity of Poupart’s ligament 
is attached, as well as the sartorius muscle, which also arises from the edge of bone 
immediately below it, whilst from the same process and from the anterior end of 
the outer lip of the iliac crest externally the tensor fasciz femoris muscle takes 
origin. 
The anterior border of the ilium stretches from the anterior superior iliac spine 
to the margin of the acetabulum below. Above, it is thin; but below, it forms a 
thick tubercular process, the anterior inferior iliac spine (spina iliaca anterior in- 
ferior). From this the rectus femoris muscle arises, whilst strong fibres of the 
ilio-femoral ligament of the hip-joint are attached to it immediately above the 
acetabular margrn. Posteriorly, the crest terminates in the posterior superior iliac 
spine (spina iliaca posterior superior). Below this, the posterior border of the bone 
is sharp and irregularly notched, terminating in a prominent angle, the posterior 
co) 
inferior iliac spine (spina iliaca posterior inferior), i in front of which the edge ot the 
