THE METATARSAL BONES. 



431 



second when present on the first, implying the presence of a bursa rather than of a 

 joint. The base of the third metatarsal fits the outer cuneiform, and is nearly 

 plane. The posterior upper border; seen from the dorsum, is oblique, running 



Dorsal 



Tuberosity 



Cuboid 



Plantar 



Fourth metatarsal 



Cuboid 



Tuberosity ( jj!g^ 



Fourth 

 metatarsal 



Cuboid 



Fig. 450. 



Right fifth metatarsal. A, distal aspect ; B, dorsal aspect ; C, plantar aspect. 



outward and backward. The inner surface has two facets for the second, and the 



outer surface one at the top for the fourth metatarsal. The base of the fourth 



metatarsal is also oblique. It has an oblong facet for the 



cuboid, and a single internal one at the top for the third, 



which is separated from the proximal end by a rough space 



for the insertion of an interosseous ligament from the tarsus. 



There is externally a triangul* facet at the upper angle 



for the fifth. This last facet is bounded in front by a deep 



groove which receives the edge of the facet on the fifth. 



The fifth metatarsal has an even more oblique base, the 



inner two-thirds of which bear a facet for the cuboid. The 



outer part is prolonged as the tuberosity beyond the edge 



of the foot, overhanging the joint. The inner side has a 



facet for the fourth metatarsal bone. 



The shafts of the metatarsal bones are flattened lat- 

 erally, but theoretically three-sided, like the first. The 

 second has an external surface looking directly outward ; a 

 superior one at the base, which twists so as to become in- 

 ternal. This is separated from the former in the distal two- 

 thirds of the shaft by a sharp ridge. The third side is internal 

 at the base, but soon becomes inferior. The shaft of the 

 third differs only slightly, the external surface looking some- 

 what upward and there being more of a ridge below. In 

 the fourth it seems as if the proximal part of the shaft had 

 been bent outward on its axis, so that the outer side looks 

 more upward and the other two are less twisted. In the 

 fifth this process has gone farther ; the originally outer side 

 is now the upper, separated by one border from the inner and by another from the 

 inferior. This last border, now external, represents the one that was the inferior 

 of the third metatarsal. The nutrieyit foramina of the four outer metatarsals are 

 in the external surfaces, running upward. They are not very constant. 



Fifth 

 metatarsal 



Cuboid 



Right fifth metatarsal, iimer 

 aspect. 



