FIBULA. 99 



head of the fibula ; and upon the posterior part of the internal tube- 

 rosity a depression, for the insertion of the tendon of the semimem- 

 branosus muscle. 



The shaft of the tibia presents three surfaces ; internal, which is 

 subcutaneous and superficial ; external, which is concave and marked 

 by a sharp ridge, for the insertion of the interosseous membrane ; and 

 posterior, grooved, for the attachment of muscles. Near the upper 

 extremity of the posterior surface is an oblique ridge, the popliteal line, 

 for the attachment of the fascia of the popliteus muscle ; and imme- 

 diately below the oblique line, the nutritious canal, which is directed 

 downwards. 



The inferior extremity of the bone is somewhat quadrilateral, and 

 prolonged on its inner side into a large process, the internal malleolus. 

 Behind the internal malleolus, is a broad and shallow groove, for lodging 

 the tendons of the tibialis posticus and flexor longus digitorum ; and 

 farther outwards another groove, for the tendon of the flexor longus 

 pollicis. Upon the outer side the surface is concave and triangular, 

 rough above, for the attachment of the interosseous ligament ; and 

 smooth below, to articulate with the fibula. Upon the extremity of 

 the bone is a triangular smooth surface, for articulating with the 

 astragalus. 



Development. By three centres ; one for the shaft, and one for 

 each extremity. Ossification commences in the tibia, immediately 

 after the femur ; the centre for the head of the bone appears soon 

 after birth, and that for the lower extremity during the second year ; 

 the latter is the first to join the diaphysis. The bone is not complete 

 until near the twenty-fifth year. Two occasional centres have some- 

 times been found in the tibia, one in the tubercle, the other in the in- 

 ternal malleolus. 



Articulations' With three bones ; femur, fibula, and astragalus. 



Attachment of Muscles. To ten ; by the internal tuberosity, to the 

 sartorius, gracilis, semitendinosus, and semimembranosus ; by the ex- 

 ternal tuberosity, to the tibialis anticus and extensor longus digitorum ; 

 by the tubercle, to the ligamentum patellae ; by the external surface of 

 the shaft, to the tibialis anticus ; and by the posterior surface, to the 

 popliteus, soleus, flexor longus digitorum, and tibialis posticus. 



FIBULA. The fibula (v'govn, a brooch, from its resemblance, in 

 conjunction with the tibia, to the pin of an ancient brooch) is the 

 outer and smaller bone of the leg ; it is long and slender in figure, 

 prismoid in shape, and, like other long bones, is divisible into a shaft 

 and two extremities. 



The superior extremity or head is thick and large, and depressed 

 upon the upper part by a concave surface, which articulates with the 

 external tuberosity of the tibia. Externally to this surface is a thick 

 and rough prominence, for the attachment of the external lateral liga- 

 ment of the knee-joint, terminated behind by a styloid process, for 

 the insertion of the tendon of the biceps. 



