130 



THE BONES OF THE LOWER LIMB. 



TUBEROSITY 



Fig. 145. RIGHT os CALCIS, FROU ABOVE. (G. D. T.) 



often subdivided into two, is placed over the sustentaculum, and is concave ; the 

 other, posterior and external to this, and larger, is convex from behind forwards and 

 outwards : the outer end of the groove is much widened, and at its fore part is a 



rough surface where the extensor 



euB"> brevis digitorum takes origin. The 



anterior extremity articulates with 

 the cuboid bone by a surface concave 

 from above, downwards and out- 

 wards, and convex in the opposite 

 direction ; and internal to this, along 

 the front of the sustentaculum tali, 

 the internal calcaneo-navicular liga- 

 ment is attached. The under surface, 

 projecting in a rough anterior 

 tubercle, gives attachment to the 

 inferior calcaneo- cuboid ligaments. 

 The external surface is on the whole 

 flat, but often presents at its fore part 

 an oblique ridge, the peroneal spine, 

 separating two slight grooves, the 

 upper for the tendon of the peroneus 

 brevis, the lower for the peroneus 

 longus. 



The astragalus, or talus, second 

 in size of the tarsal bones, receives 

 the weight of the body from the 

 leg. It articulates with the tibia 

 above and internally, the fibula ex- 

 ternally, the os calcis below, and the 

 navicular in front. Its longest axis 

 is directed forwards and inwards. 

 Its main part is called the l>ody, the 

 convex anterior extremity is the head, 

 and the grooved part behind this is 

 the neck. The superior articular 

 surface occupies the whole of the 

 upper aspect of the body, and sends 

 a prolongation downwards on each 

 of the lateral surfaces of the bone. 

 The middle part, looking upwards 

 to the tibia, is convex from before 

 backwards, broader in front than 

 behind, with its outer margin longer 

 than the inner, and curved, while 

 the inner is straight. The inner 

 lateral part is narrow, sickle-shaped, 



and articulates with the internal malleolus ; the outer lateral part, much deeper, 

 triangular, and concave from above down, articulates with the external malleolus. 

 Inferiority, there are two smooth surfaces, which articulate with the calcaneum. 

 The posterior of these, the larger, concave from within outwards and forwards, is 

 separated by a rough depression for the interosseous ligament from the convex 

 anterior surface, which rests on the sustentaculum tali. The rounded anterior sur- 

 face of the head articulates with the navicular bone ; and at the lower and inner 



INT. CALC. NAV.-LLGT. 



CALCANEUM 



Fig. 146. RIGHT ASTRAGALUS, FROM RELOW. (G. D. T. ) 



