CONSTRUCTION OF THE FOOT AS A WHOLE. 211 



The phalanges of the first row resemble closely those of the hand. The shaft 

 is compressed from side to side, convex above, concave below. The posterior 

 extremity is concave ; and the anterior extremity presents a trochlear surface, for 

 articulation with the second phalanges. 



The phalanges of the second row are remarkably small and short, but rather 

 broader than those of the first row. 



The ungual phalanges in form resemble those of the fingers ; but they are 

 smaller, flattened from above downward, presenting a broad base for articulation 

 with the second row, and an expanded extremity for the support of the nail and 

 end of the toe. 



Articulation. The first row, with the metatarsal bones behind and second 

 phalanges in front ; the second row of the four outer toes, with the first and third 

 phalanges ; of the great toe, with the first phalanx ; the third row of the four 

 outer toes, with the second phalanges. 



Attachment of Muscles. To the first phalanges. Great toe, five muscles: 

 innermost tendon of Extensor brevis digitorum, Abductor hallucis, Adductor 

 obliquus hallucis, Flexor brevis hallucis, Adductor transversus hallucis. Second 

 toe, three muscles : First and Second dorsal interosseous and First lumbrical. 

 Third toe, three muscles : Third dorsal and First plantar interosseous and Second 

 lumbrical. Fourth toe, three muscles : Fourth dorsal and Second plantar inter- 

 osseous and Third lumbrical. Fifth toe, four muscles : Flexor brevis minimi 

 digiti, Abductor minimi digiti, and Third plantar interosseous, and Fourth 

 lumbrical. Second phalanges! Great toe ; Extensor longus hallucis, Flexor 

 longus hallucis. Other toes ; Flexor brevis digitorum, one slip of the common 

 tendon of the Extensor longus and brevis digitorum. 1 Third phalanges : two slips 

 from the common tendon of the Extensor longus and Extensor brevis digitorum^ 

 and the Flexor longus digitorum. 



Development of the Foot (Fig. 151). 



The Tarsal bones are each developed by a single centre, excepting the os calcis, 

 which has an epiphysis for its posterior extremity. The centres make their appear- 

 ance in the following order : os calcis, at the sixth month of foetal life ; astragalus, 

 about the seventh month ; cuboid, at the ninth month ; external cuneiform, 

 during the first year ; internal cuneiform in the third year ; middle cuneiform and 

 navicular in the fourth year. The epiphysis for the posterior tuberosity of 

 the os calcis appears at the tenth year, and unites with the rest of the bone soon 

 after puberty. 



The Metatarsal bones are each developed by two centres : one for the shaft 

 and one for the digital extremity in the four outer metatarsal ; one for the shaft 

 and one for the base in the metatarsal bone of the great toe. 2 Ossification 

 commences in the centre of the shaft about the ninth week, and extends toward 

 either extremity. The centre in the proximal end of the first metatarsal bone 

 appears about the third year, the centre in the distal end of the other bones 

 between the fifth and eighth years; they become joined between the eighteenth and 

 twentieth years. 



The Phalanges are developed by two centres for each bone : one for the shaft 

 and one for the metatarsal extremity. The centre for the shaft appears about the 

 tenth week, that for the epiphysis between the fourth and tenth years; they join 

 the shaft about the eighteenth year. 



Construction of the Foot as a Whole. 



The foot is constructed on the same principles as the hand, but modified to form 

 a firm basis of support for the rest of the body when in the erect position. It 



1 Except the second phalanx of the fifth toe, which receives no slip from the Extensor brevis 

 digitorura. 



2 As was noted in the first metacarp.-il bone, so in the first metatarsal, tliere is often to be observed 

 a tendency to the formation of a second epiphysis in the distal extremity. (See footnote, p. 171.) 



