432 



HUMAN ANATOMY. 



Fig. 451. 



Os intermetatarseum 



The heads of the metatarsal bones are compressed, hke the shafts, from side 

 to side, and have each a pair of lateral tubercles at the dorsal aspect of the end of 

 the shaft, separated by a groove from the articular surface. Lateral ligaments are 



attached both to the tubercles and the grooves. The ar- 

 ticular surface is oblong, extending well onto the plantar 

 side, where it ends in two lateral prolongations, of which 

 the outer is the more prominent. A line connecting their 

 ends would be oblique to the shaft, especially in the outer 

 toes. 



Fusion of the outer cuneiform with its metatarsal occurs 

 occasionally at the plantar aspect. It is probably con- 

 genital. Pfitzner has seen it at seventeen and we at 

 nineteen. 



Development. — Centres for the shafts of the meta- 

 tarsals appear towards the end of the third month of foetal 

 life. A proximal epiphysis for the first and distal ones for 

 the others appear in the third year, fusing at about seven- 

 teen. Occasionally the metatarsals, especially the first, 

 have an epiphysis at each end. 

 Os Intermetatarseum. — This is an occasional wedge-shaped bone found on 

 the dorsal aspect of the foot, between the internal cuneiform and the first and second 

 metatarsals. It may articulate with all three, or with any of them, or be attached to 

 them by connective tissue. More often it is connected by bone with one of the three 

 neighbors, especially with the internal cuneiform, of which it may seem to be a pro- 

 cess (Fig. 451). It is found in some form once in ten feet (Pfitzner). 



Intermetalarsalbone fused with 

 right internal cuneiform. 



Fig. 452. 



Third, distal 

 or ungual, 

 phalanx 



Second, or 

 middle, 

 phalanx 



THE FHALANGPIS. 



There are two for the great toe and three for each of the others. Although of 

 very different proportions, they present the features which have been described for 

 those of the hand, especially the shape of the articular sur- 

 faces. The first phalanx of the great toe is about as 

 long as that of the thumb and nearly twice as broad. There 

 is a tubercle for muscular insertion at each side of the pal- 

 mar aspect of the base. The terminal phalanx of the 

 great toe is also very massive. The first, or proximal, pha- 

 langes of the other toes diminish in length from within out- 

 ward. Those of the second row are so short as to be 

 almost cubical, although they are broader than thick. The 

 terminal, or distal, phalanges are very rudimentary. 

 Pfitzner^ has shown that in about one-third of the cases the 

 terminal phalanx of the little toe is fused with the middle 

 one, even before birth. Presumably they never were distinct 

 in the embryo. As he has found this condition in Egyptian 

 mummies, certain very pessimistic views as to the degener- 

 ation in store for the human foot are probably unwarranted. 



Sesamoid Bones.— Those of the first metatarso- pha- 

 langeal joint are large and constant ; those of the same joint 

 in the other toes very rare. The least uncommon are those 

 of the fifth toe, of which the inner sesamoid is found in 5.5 

 per cent, and the outer in 6.2 per cent. A sesamoid of the 

 interphalangeal joint of the great toe is found in 50.6 per 

 cent. (Pfitzner^). 



Development.— The first nucleus to appear is that of 

 the distal phalanx of the great toe at the end of the third 

 foetal month. Those of the other distal phalanges, except the fifth, come some two 

 weeks later. The bones of the proximal row seem to ossify rather later than the 



^ Arch, fiir Anat. und Entwick., 1890. 

 ' Morph. Arbeiten, Bd. i. 



First, or 

 proximal, 

 phalanx 



Phalanges of right second 

 toe, plantar surface. 



