122 



FIBULA. 



Fig. 59.' 



The shaft of the tibia presents three sarfac.es ; 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 mus 

 cle ; and immediately below the oblique line, the nutritious 

 canal, which is directed downwards. 



The inferior extremity of the bone is somewhat quadri- 

 lateral, 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 con- 

 cave 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 trian- 

 gular smooth surface, for articulating \vith 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 

 or 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 sometimes been found in the ti- 

 bia, one in the tubercle, the other in the internal malleolus. 



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

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

 torius, gracilis, semitendinosus, and semimembranosus ; by the external 

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

 tubercle, to the ligamentum patella? ; 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 (ire^ni, a brooch, from its resemblance, in con- 

 junction with the tibia, to the pin of an ancient brooch) is the outer and 

 smaller bone of the leg; it is lon^ 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 ligament of the knee- 

 jomt, terminated behind by a styloid process, for the insertion of the ten- 

 don of the biceps. 



The lower extremity is flattened from without inwards, and prolonged 



* The tibia and fibula of the right leg, articulated and seen from the front. 1. The 

 shaft of tne tibia. 2. The inner tuberosity. 3. The outer tuberosity. 4. The spinous 

 process 5. The tubercle. 6. The internal or subcutaneous surface of the shaft. 7. The 

 lower extremity of the tibia. 8. The internal malleolus. 9. The shaft of the fibula. 

 10. Its upper extremity. 11. Its lower extremity, the external malleolus. The sharp 

 Lorder oetween 1 and 6 is the crest of the tibia. 



