L26 



THE BONES OF THE LOWER LIMB. 



interval, depressed in front and behind, where it gives attachment to the crucial 

 ligaments and the semilunar fibro-cartilages of the knee-joint, and elevated in the 

 middle, thus forming the spine, which is received into the intercondylar notch of 

 the femur. The summit of the spine presents two compressed tubercles, with a 

 slight intervening hollow, and the condylar articular surfaces are prolonged upwards 

 on the sides of the process. The depressed surface behind the spine is continued 

 into a shallow excavation the popliteal notch, which separates the tuberosities on 

 the posterior aspect of the head. Lower down on the front of the bone, at the 

 junction of the head and shaft, is situated the tubercle or anterior tuberosity, 

 marked by the attachment of the ligamentum patellae. 



The shaft of the tibia is three-sided, and diminishes in size as it descends for 

 about two-thirds of its length, but increases somewhat towards its lower extremity. 

 The internal surface is convex and for the most part subcutaneous ; at the upper 



Fig. 141. UPPER EXTREMITY OP THE RIGHT 

 TIBIA, FROM ABOVE. (Drawn by T. W. P. 

 Lawrence. ) | 



Fig. ] 42. TRANSVERSE SECTION THROUGH THE 



MIDDLE OF THE BONES OF THE LEG, WITH THK 

 INTEROSSEOUS MEMBRANE. (G. D. T.) 



end, by the side of the tubercle, is a slight roughness where the tendons of the 

 sartorius, gracilis and semitendinosus muscles are inserted. It is separated from 

 the external surface by the anterior border, which runs with a sinuous course from 

 the tubercle to the front of the internal malleolus, having its concavity directed 

 outwards above, and inwards below ; in its upper two-thirds it forms a sharp ridge 

 known as the crest of the tibia ; in its lower third it is smooth and rounded. The 

 external surface is slightly hollowed in its upper two-thirds, where it lodges the 

 belly of the tibialis anticus muscle ; but below the point where the crest disappears 

 it turns forwards, becomes convex, and is covered by the extensor tendons. The 

 posterior surface is crossed obliquely in its upper third by the rough popliteal or 

 oblique line, which runs downwards and inwards from the outer tuberosity, and gives 

 origin to the soleus muscle : above this is a triangular area occupied by the popliteus 

 muscle ; while below the line, in the middle third of the shaft, a longitudinal 

 ridge divides the surface into two portions, an inner giving origin to the flexor 

 longus digitorum, and an outer, larger, to the tibialis posticus. A little below the 

 oblique line, and external to the longitudinal ridge, is a large foramen for the 

 medullary artery, directed downwards into the bone. The posterior surface is 

 separated from the internal by the internal border, which is most distinct in the 

 middle third of the bone, being rounded off above and below, and from the outer 

 surface by the external border or interosseous ridge, a prominent edge or line, inclined 

 forwards above, to which the interosseous membrane is attached. 



The inferior extremity, much smaller than the superior, is expanded trans- 



