THE LEG. 219 



face, which is continuous with the articular surface for the as- 

 tragalus, and is consequently a part of the cavity of the ankle 

 joint. Just above this lunated surface the bone is rough for the 

 origin of short ligamentous fibres, which unite it to the fibula. 



The body of the tibia commences just below the enlarged up- 

 per extremity, and terminates near the ankle. In the front view 

 of it, it diminishes continually in descending, in its superior two- 

 thirds: afterwards it enlarges gradually to the lower extremity; 

 in the lateral view it diminishes downwards almost to the lower 

 extremity. It is slightly bent forwards, and is generally prisma- 

 tic, more particularly above: one of its faces is internal, another 

 external, and the third posterior. The internal face is rounded, 

 and, with the exception of its upper part, where the flexor ten- 

 dons are inserted, it is only covered by the skin. Its external 

 face is flat, excepting below, where it is rounded and is covered 

 by the muscles on the front of the leg. The posterior face is 

 slightly rounded, except at its upper part where it is crossed by 

 a line running obliquely from the articular surface for the fibula, 

 downwards and inwards : above which line, is the superficial 

 triangular depression for the popliteus muscle. 



The three sides of the tibia are marked off from each other 

 by ridges of bone. The anterior ridge, called the spine or crest, 

 begins at the external margin of the tubercle for the insertion 

 of the tendon of the patella, and may be traced very distinctly, 

 in the form of an S very slightly curved, almost to the malleo- 

 lusinternus: it is more elevated in its middle. The external 

 ridge is a straight line running from one extremity of the bone 

 to the other; to it is attached one edge of the interosseous liga- 

 ment. The internal ridge is rounded, but also runs the whole 

 length of the body of the bone, being more distinct below. The 

 internal lateral ligament of the knee and the soleus muscle are 

 attached to it, above; and below, the flexor longus digitorum 

 pedis. 



Foramina large and small, for blood vessels and fibres, are 

 found on the circumference of both extremities of the tibia. On 

 its posterior face, about one-fourth of its length from the head, 

 is a large canal sloping downwards, through which passes the 

 nutritious artery. Its structure, like that of the other long bones, 



