194 



THE SKELETON 



stricted part of the bone supporting the head. Above it is rough, and perforated by numerous 

 vascular foramina. Below, it presents a deep groove [sulcus tali], directed from behind forward 

 and lateralward. When the talus is articulated with the calcaneus, this furrow is converted 

 into a canal [sinus tarsi] in which is lodged the interosseous talo-calcaneal ligament. The head 

 is the rounded anterior end of the bone, and its large articular surface is divisible into three 

 parts: in front, a smooth, oval convex area, directed downward and forward for the navicular 

 bone; below, an elongated facet, convex from front to back, for articulation with the sustentacu- 

 lum tali of the calcaneus; and between these, is a small facet which rests on the calcaneo- 



FiG. 230. — The Left Talus. (Plantar view.) 



Body 



Neck 



Head 



T — Groove for the flexor hallucis longus 



-^ — —For calcaneus 



For the sustentaculum tali 



For the calcaneo-navicular (or the 

 spring) ligament 



For navicular 



navicular ligament, separated from it by the synovial membrane of the talo-calcaneo-navicular 

 joint. 



Articulations. — The talus articulates with four bones and two ligaments. Above and 

 medially with the tibia, below with the calcaneus, in front with the navicular, laterally with the 

 fibula. The head articulates with the calcaneo-navicular ligament and the lateral border of 

 the superior surface, at its posterior part, with the transverse ligament of the inferior tibio- 

 fibular joint. 



The talus is a very vascular bone and is nourished by the dorsalis pedis artery and its tarsal 

 branch. It gives attachment to no muscles. 



Fig. 231. — A Talus with the Os Trigonum. 

 Os trigonum 



Ossification. — The talus is ossified from one, occasionally from two, nuclei. The principal 

 centre for this bone appears in the middle of the cartilaginous talus at the seventh month of 

 intra-uterine life. Tlie additional centre is deposited in the posterior portion of the bone, and 

 forms the lateral posterior (uberrlc which may remain separate from the rest of the bone and 

 form the os trigonum. At birth, the talus presents some important i)eculiarities in the disposi- 

 tion of the articular facet on the tibial side of its body, and in the obliquity of its neck. If, in the 

 adult talus, a line be drawn through the niifldle of the superior trochlear surface parallel with 

 its medial border, and a second line bo drawn along the lateral side of the neck of the bone so as 

 to intersect the fir.st, the angle formed by these two lines will express the obliquity of the neck 

 of the bone. This in the adult varies greatly, but the average may be taken as 10°. In the 



