104 



BONES OF THE LOWER LIMB. 



somewhat smaller than the other, is marked posteriorly by a flat surface 

 which articulates with the fibula, while the inner presents a groove for 

 the insertion of the semi-membranosus muscle. Lower down, in front, is 

 situated the anterior tuberosity or tubercle, rough inferiorly, where it gives 

 attachment to the ligamentum patellee, and smooth above, where it is 

 covered by a synovial bursa. 



Fig. 



Fig. 96. EIGHT TIBIA FROM BEFORE. 



1, shaft, and shin or anterior border ; 2, inner tube- 

 rosily ; 3, outer tuberosity ; 4, inner, and 5, outer, 

 condyloid articular surface ; 6, crucial spine, with fossa 

 at its root in front ; 7, anterior tuberosity or tubercle ; 

 8, lower articular surface for astragalus ; 9, malleolus 

 iuternus. 



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 sur- 

 face is convex and subcutaneous, except at the 

 upper part, where it is crossed by the tendons 

 of the sartorius, gracilis, and semitendinosus 

 muscles. It is separated from the external sur- 

 face by a sharp subcutaneous, slightly sinuous 

 crest, the shin ridge, which descends from the 

 anterior tuberosity, and is smoothed away in the 

 inferior third of the bone. The external surface 

 is slightly hollowed in the larger part of its 

 extent, where it gives origin to the tibialis 

 anticus muscle ; but beneath the point where the 

 crest disappears it turns forwards, becomes 

 convex, and is covered by the extensor tendons. 

 The posterior surface is traversed obliquely in its 

 upper third by the popliteal line a rough mark 

 which extends upwards and outwards to the 

 external tuberosity, giving attachment to the 

 soleus muscle, and separating a triangular area, 

 in which the popliteus muscle lies, from the 

 space below, which gives origin to the flexor 

 longus digitorum and tibialis posticus. Inter- 

 nally, the posterior surface is separated from the 

 internal by a smooth rounded border; while on 

 its external side is a sharp ridge, inclined 

 forwards above, to which the interosseous mem- 

 brane is attached. Near the popliteal line is a 

 u\ large medullary foramen, directed downwards 



into the interior of the bone. 



The inferior extremity, much smaller than the 

 superior, is expanded transversely, and projects 

 downwards on its inner side, so as to form a 



thick process, the internal malleolus. Inferiorly it presents for articulation 

 with the astragalus a cartilaginous surface, which is quadrilateral, concave 

 from before backwards, and having its posterior border narrower and pro- 



