736 



MAMMALIAN ANATOMY 



The head is more spherical than in the cat, but when seen from the 

 side has a similar outline. The external surface is prominent for the 

 attachment of the biceps muscle and the long external lateral liga- 

 ment ; it lacks the deep vertical groove. The 

 superior surface is almost circular ; the articular 

 facet for the tibia is at the posterior part. The 

 styloid process is much more strongly developed, 

 and to it is attached the short external lateral 

 ligament. To the anterior part of the head is 

 fastened the peroneus longus, and to the posterior 

 part, the outer head of the soleus muscle. 



The borders on the shaft are all more clearly 

 marked than they are in the cat, hence the bone 

 is irregularly quadrilateral on cross-section. 



The anterior-external border begins at the 



O 



inner anterior side of the head, in common with 

 the anterior-internal border. In its upper part it 

 is obscure, but lower down it becomes very sharp 

 and prominent. In the lower fourth it bifurcates, 

 one branch going straight down as the anterior 

 border of the lower extremity, the other passing 

 downward and backward on the outer surface 

 of the malleus. The triangle between the two 

 branches is subcutaneous. 



The anterior-internal border or interosseous 



ridge is not distinct from the anterior-external border in the upper 

 fourth ; lower down, however, it gradually diverges. In the lower 

 fourth it is joined by the posterior-internal border, and then terminates 

 at the apex of a rough triangle above the malleolar articular surface. 

 It gives attachment to the strong interosseous membrane. 



The posterior-internal border begins above at the posterior inner 

 side of the head, and after taking a somewhat sinuous course terminates 

 below in the anterior-internal border. It is particularly prominent at 

 the middle of the bone, where it is pierced by the nutrient artery. It 

 is sometimes called the oblique line of the fibula. 



The posterior-external border begins above at the outer side of 

 the head and passes to the posterior side of the shaft, and terminates 

 as the posterior border of the malleolus. 



LEFT FIBULA AND TIBIA, 

 ANTERIOR VIEW. 



1, shaft of the tibia; 2, 3, 

 tuberosities ; 4, spine; 5, tu- 

 bercle ; 6, crest of shin ; 7, 

 lower extremity of the bone ; 

 8, internal malleolus; 9, shaft 

 of the fibula; 10, its head; 

 11, external malleolus. 



