BONES OF THE FOOT. 



341 



whose long axis is vertical, it is articulated 

 with the anterior and internal part of the navi- 

 cular bone, and in front a large and irregular, 

 slightly concave articular facet adapts it to the 

 posterior extremity of the metatarsal bone of 

 the great toe. Its inner surface is convex and 

 rough for ligamentous insertion ; on it, towards 

 its anterior part, we observe an impression, 

 sometimes an eminence, for the insertion of 

 the tibialis anticus tendon; and its plantar 

 surface, the base of the wedge, is thick and 

 prominent, and affords insertion to ligamentous 

 fibres as well as to those of the tibialis posticus 

 tendon. The external surface is articulated in 

 front with the second metatarsal bone, and 

 behind with the middle cuneiform, by means 

 of an oblong articular facet, which extends 

 along the upper part of this surface from before 

 backwards parallel to the acute edge. The 

 remainder of the external surface is rough for 

 ligamentous insertion, excepting a small por- 

 tion about the sixth of an inch broad, which, 

 extending along the posterior edge, is articular 

 and continuous with the posterior surface of 

 the bone. 



The middle or second cuneiform bone is the 

 smallest of the three ; its base is uppermost, 

 rough and convex ; its posterior surface is tri- 

 angular with the base superior; it is articular 

 and adapted to the middle facet on the anterior 

 surface of the navicular; its anterior surface is 

 also triangular and articulated with the second 

 metatarsal bone ; its inner surface is articular 

 along its upper and posterior edges, and rough 

 in the remainder of its extent; this surface is 

 in contact with the inner cuneiform. The outer 

 surface is articular along half of its upper edge 

 and the whole of its posterior, but rough in 

 the remainder, and by means of the articular 

 portions is connected with the external cunei- 

 form bone. 



The external or third cuneiform bone is 

 second in point of size ; it is bounded on the 

 outside by the cuboid, behind by the navicular, 

 on the inside by the middle cuneiform, and in 

 front by the third metatarsal bone. Its pos- 

 terior and anterior surfaces are both plane and 

 articular, the one for the navicular, the other 

 for the third metatarsal bone. The base of the 

 wedge is situated on the dorsal surface of the 

 foot, and is rough. The internal surface 

 presents at its posterior edge a facet for arti- 

 culation with the middle cuneiform, and in 

 front another for the second metatarsal ; the re- 

 mainder is non-articular. The external surface 

 presents, towards its upper and posterior angle, 

 a plane triangular facet, which is adapted to a 

 similar one on the inner surface of the cuboid, 

 but in the rest of its extent it is rough and non- 

 articular. 



Structure of the tarsal bones. Like all the 

 short bones, those of the tarsus are composed 

 of a mass of spongy tissue surrounded by a 

 thin and papyraceous layer of compact. Hence 

 these bones are remarkable for their extreme 

 lightness. 



Developement. In the third month the 

 cartilaginous framework of these bones is 

 already apparent. The largest two begin to 



ossify before birth ; the os calcis commences at 

 from the fifth to the seventh month, by a single 

 point of ossification situate about the middle of 

 the bone rather nearer to its anterior part, and the 

 ossification is not completed till eight or ten years 

 after birth, when another point appeal's in the 

 posterior part of the bone, and by the extension 

 of it to the first point, which is finished about 

 the fifteenth year, the process is completed. 

 The ossification of the astragalus commences 

 about the sixth month. The cuboid and navi- 

 cular begin to ossify immediately after birth 

 by one point each, and the three cuneiform 

 bones are ossified, the internal about the end 

 of the first year, die middle and external about 

 the fourth year. 



II. Metatarsus (der Mittelfuss). This seg- 

 ment of the foot is composed of five bones 

 placed parallel to each other in front of the 

 tarsus, with which their posterior extremities 

 are articulated. These bones are distinguished 

 numerically, counting from within outwards ; 

 a distinct interosseous space intervenes between 

 each pair of bones, which in the recent state is 

 filled by muscle. From the arched form of 

 the tarsus, the metatarsus naturally takes a 

 similar arrangement by reason of its articula- 

 tion with it, and consequently we observe that 

 it is convex on its dorsal surface and concave 

 on its plantar. 



The raetatarsal bones possess certain general 

 characters in common; they belong to the class 

 of long bones, and consequently each has its 

 shaft and two extremities. The shaft in all is 

 prismatic, slightly curved, convex on the dor- 

 sal, concave on the plantar surface; two of the 

 surfaces of the shaft are lateral, and correspond 

 to interosseous spaces ; the third is superior, 

 and corresponds to the dorsum of the foot. 



The posterior or tarsal extremity of each 

 metatarsal bone is wedge-shaped, the base of 

 the w : edge being on the dorsal aspect. Three 

 articular facets may be noticed on each, ex- 

 cepting the first and fifth. The posterior of 

 these is triangular and plane, articulated with 

 the tarsal bones ; the remaining two are lateral, 

 and adapted to corresponding ones on the 

 metatarsal bones on each side. 



The anterior or digital extremity of each 

 metatarsal bone presents an articular head or 

 condyle, flattened upon the sides, oblong from 

 above downwards, and much more extended 

 inferiorly or in the direction of flexion than 

 superiorly or in that of extension. This is 

 articulated with the posterior extremity of the 

 metatarsal phalanx. On each side of the con- 

 dyle there is a depression, and behind that 

 an eminence to which the lateral ligament of 

 the metatarso-phalangeal joint is attached. 



In addition to the characters above men- 

 tioned, there are certain special characters 

 belonging to particular metatarsal bones which 

 enable us to distinguish them from each 

 other. 



The first, or metatarsal of the great toe, is 

 distinguished, 1. by its considerable size and 

 its being the shortest of the five bones; 2. its 

 tarsal extremity is semilunar and concave, and 

 has no lateral articular facet; 3. its digital 



