FIBULA. 



247 



Fig. 178. Plan of the Development of the 

 Tibia. By Three Centres. 



rt at birth 



at 2, 



r oins Sliaft about 

 ' 



Joins S/inft a l>ou,* 



lower epiphysis joins the shaft at about the twentieth year, and the upper 

 one about the twenty-fifth year. Two additional centres occasionally exist, 

 one for the tongue-shaped process of 

 the upper epiphysis, the tubercle, and 

 one for the inner malleolus. 



Articulations. With three bones: 

 the femur, fibula, and astragalus. 



Attachment of Muscles. To the inner 

 tuberosity, the Semi-membranosus; to 

 the outer tuberosity, the Tibialis An- 

 ticus and Extensor Longus Digitorum ; 

 to the shaft, its internal surface, the 

 Sartorius, Gracilis, and Semi-tendino- 

 sus; to its external surface, the Tibia- 

 lis Anticus; to its posterior surface, 

 the Popliteus, Soleus, Flexor Longus 

 Digitorum, and Tibialis Posticus; to 

 the tubercle, the ligamentum patella?. 



THE FIBULA. (Figs. 176, 177.) 



The Fibula is situated at the outer 

 side of the leg. It is the smaller of 

 the two bones, and, in proportion to 

 its length, the most slender of all the 

 long bones; it is placed nearly parallel 

 with the tibia. Its upper extremity is 

 small, placed below the level of the 

 knee-joint, and excluded from its for- 

 mation; the lower extremity inclines a little forwards, so as to be on a plane 

 anterior to that of the upper end, projects below the tibia, and forms the outer 

 ankle. It presents for examination a shaft and two extremities. 



The Upper Extremity, or Head, is of an irregular rounded form, presenting 

 above a flattened articular facet, directed upwards and inwards, for articulation 

 with a correspondiug facet on the external tuberosity of the tibia. On the 

 outer side is a thick and rough prominence, continued behind into a pointed 

 eminence, the styloid process, which projects upwards from the posterior part 

 of the head. The prominence gives attachment to the tendon of the Biceps 

 muscle, and to the long external lateral ligament of the knee, the ligament 

 dividing the tendon into two parts. The summit of the styloid process gives 

 attachment to the short external lateral ligament. The remaining part of the 

 circumference of the head is rough, for the attachment, in front, of the anterior 

 superior tibio-fibular ligament, and the upper and anterior part of the Peroneus 

 Longus; and behind, to the posterior superior tibio-fibular ligament, and the 

 upper fibres of the outer head of the Soleus muscle. 



The Lower Extremity, or External Malleolus, is of a pyramidal form, somewhat 

 flattened from without inwards, and is longer, and descends lower, than the in- 

 ternal malleolus. Its external surface is convex, subcutaneous, and continuous 

 with a triangular (also subcutaneous) surface on the outer side of the shaft. 

 The internal surface presents in front a smooth triangular facet, broader above 

 than below, and convex from above downwards, which articulates with a corre- 

 sponding surface on the outer side of the astragalus. Behind and beneath the 

 articular surface is a rough depression, which gives attachment to the posterior 

 fasciculus of the external lateral ligament of the ankle. The anterior border is 

 thick and rough, and marked below by a depression for the attachment of the 

 anterior fasciculus of the external lateral ligament. The posterior border is broad 

 and marked by a shallow groove, for the passage of the tendons of the Pero- 



