214 OS NAVICULARE. 



which ligament, and on the edge of this bone to which it is 

 fixed, the groove is formed for the tendon of the flexor digito- 

 rum profundus. 



The lower surface of this bone is flat at the back part, and 

 immediately before this plane, there are two tubercles, from 

 the internal of which the musculus abductor pollicis, flexor 

 digitorum sublimis, as also part of the aponeurosis plantaris, 

 and of the abductor minimi diglti, have their origin ; and the 

 other part of the abductor minimi digiti and aponeurosis plan- 

 taris rises from the external. Before these protuberances, this 

 bone is concave, for lodging the flexor muscles ; and, at its 

 forepart, we may observe a rough depression, from which, 

 and a tubercle behind it, the ligament goes out that prevents 

 this bone from being separated from the os cuboides. 



The forepart of the os calcis is formed into an oblong pulley- 

 like smooth surface, which is circular at its upper external end, 

 but is pointed below. The smooth surface is fitted to the os 

 cuboides. 



Though the surfaces by which the astragalus and os calcis 

 are articulated, seem fit enough for motion, yet the very strong 

 ligaments, by which these bones are connected, prevent much 

 motion, and give firmness to this principal part of our base, 

 which rests on the ground. 



Os naviculare is somewhat oval. It is formed into an 

 oblong concavity behind, for receiving the anterior head of the 

 astragalus. The upper surface is convex. Below, the surface 

 is very unequal and rough ; but hollow for the safety of the 

 muscles. Its internal extremity is very prominent. The 

 abductor pollicis takes in part its origin from it, the tendon of 

 the tibialis posticus is inserted into it, and to it two remarkable 

 ligaments are fixed ; the first is the strong one, formerly men- 

 tioned, which supports the astragalus ; the second is stretched 

 from tliis bone obliquely across the foot, to the metatarsal bones 

 of the middle toe, and of the toe next to the little one. On the 

 outside of the os naviculare there is a semicircular smooth 

 surface, where it is joined to the os cuboides. The forepart of 

 this bone is covered with cartilage, and divided into three 

 smooth planes, fitted to the three ossa cuneiformia. 



