THE METATARSUS. 



183 



presents a smooth facet, covered with cartilage in the recent state, where the tendon 

 of the peroneus longus turns round into the sole. Between the tuberosity and the 

 anterior margin of this surface is a deep groove, beginning at a notch in the outer 

 border of the bone, for the reception of the tendon. Behind the tuberosity is a 

 triangular depressed area occupied by the plantar calcaneo-cuboid ligament. 



Varieties. Instances are recorded in which the number of tarsal bones is reduced owing 

 to congenital synostosis of the os calcis and navicular. of the astragalus and os calcis, or of the 

 astragalus and navicular. An increase in number may arise from the separation of the 

 external tubercle at the back of the astragalus (<>* trigunum Bardeleben), or of the tuberosity 

 of the navicular bone, from the division of the internal cuneiform bone into dorsal and 

 plantar pieces, and from the presence of a supernumerary ossicle at the fore and inner part of 

 the os calcis, or between the internal cuneiform and second metatarsal bones. (H. Leboucq, 

 " De la soudure congenitale de certains os du tarse," Bull, de 1'Acad. Koy. de Med. de Belgique, 

 1890, 103 ; L. Stieda, " Der Talus und das Os trigonum Bardelebens beim Menschen," Anat. 

 Anzeiger, 1889, 305 ; W. Gruber, " Os cuneiforme I. bipartitum beim Menschen," Mem. Acad. 

 St. Petersburg, 1877 ; Hartmann et Mordret, " Anatomie du premier cuneiform," Bull. Soc. 

 Anat. de Paris, 1889, 71.) 



THE METATABSUS. 



The five metatarsal bones are distinguished by numbers, according to their 

 position from within outwards. They resemble the metacarpal bones of the hand in 

 being long bones, slightly convex from end to end on the dorsal aspect, in having 

 differently shaped bases, three-sided shafts, and rounded heads which articulate 

 with the phalanges. They also agree with the metacarpal bones in the number of 

 bones with which each articulates. 



The first metatarsal bone is the shortest, but is much thicker and more 

 massive than the others. On its base is a large kidney-shaped surface, slightly 



concave, for articulation with the internal cunei- 

 form bone, and sometimes there occurs a small 

 facet on the outer side for the second metatarsal 

 bone. The lower part of the base forms the tube- 

 w rosity, which projects downwards and outwards in 

 the sole, and is marked on its outer side by a 

 rounded impression for the peroneus longus : on 

 the inner side is a smaller mark where a slip of the 

 tibialis anticus is inserted. Of the three surfaces 



Fig. 152. FIRST METATARSAL BONE OP 



BIGHT FOOT : PLANTAR ASPECT. (G. D. T.) 



?ig. 153. BASES OF THE METATARSAL BONES, 



FROM BEHIND. (Q. D. T.) 



of the shaft, the superior, which looks also inwards, is oblong and convex, the 

 inferior is concave, and the external, the largest, is triangular and flattened. The 

 head is large, and has on its under surface a median ridge, separating two grooves in 

 which the sesamoid bones glide. 



