110 BONES OF THE LOWER LIMB. 



looking upwards, which in the middle three projects between the dorsal 

 interosseous muscles on each side. 



The heads, smaller than the tarsal extremities, are marked on their sides 

 by depressions and tubercles. Their articular surfaces, smooth and convex, 

 are prolonged on the inferior aspect, where they terminate in bifid margins. 

 That of the first metatarsal bone presents inferiorly a ridge in the middle, 

 with grooved depressions placed one on each side and corresponding to the 

 position of the sesamoid bones. 



THE PHALANGES. 



The phalanges of the toes so closely correspond in general conformation 

 with those of the fingers that it will only be necessary in this place to state 

 the points in which they differ from the latter. 



The phalanges of the four outer toes are much smaller than the corres- 

 ponding phalanges of the hand ; but those of the great toe are larger than 

 those of the thumb. The shafts of the first row of phalanges in the four 

 outer toes are compressed laterally and narrowed in the middle ; those of 

 the second row, more especially the fourth and fifth, are very short, and 

 consist of little beyond what is necessary to unite their articular extremities. 

 The last two phalanges of the little toe are in adults not unfrequently 

 connected by bone into one piece. 



SESAMOID BONES. Two sesamoid bones lie side by side in the plantar 

 wall of the first metatarso-phalangeal joint, and glide in the grooves on the 

 head of the first metatarsal bone. Small sesamoid bones sometimes occur 

 in the corresponding joints of the other toes. 



THE BONES OF THE FOOT AS A WHOLE. 



The foot is narrowest at the heel, and as it passes forwards becomes 

 broader as far as the heads of the metatarsal bones. The posterior extremity 

 of the calcaneum is inclined inwards and backwards. The astragalus, 

 overhanging the sustentaculum tali, inclines inwards from the calcaneum so 

 much that its external superior angle is directly over the middle line of the 

 calcaneum, and hence the internal malleolus appears more prominent than 

 the external. The foot is arched from behind forwards, the posterior pier 

 of the arch being formed by the heel, the anterior by the balls of the toes. 

 The arch, indeed, may be considered as double in front, with a common 

 support behind. The internal division of the arch is that which bears the 

 greater part of the weight of the body, and is most raised from the ground ; 

 it consists of the calcaneum in its posterior two thirds, the scaphoid and 

 cuneiform bones, and the three inner toes ; the outer arch is formed by the 

 calcaneum in its whole length, the cuboid bone, and the fourth and fifth 

 toes, a great part of which rests upon the ground in standing. Besides being 

 arched longitudinally, the foot presents likewise a transverse arch formed by 

 the cuboid and three cuneiform bones and the metatarsal bones. 



DEVELOPMENT OF THE LOWER LIMB. 



The early stages of development in the lower limbs are similar to those which have 

 been already described in connexion with the upper. 



OSSIFICATION. The innominate bone is formed from the three principal pieces 

 previously mentioned, viz., the ilium, ischium, and os pubis, and various others of an 

 epiphysal nature. The deposit of bone commences in the cartilaginous piece of the 

 ilium a little later than in other large bones ; it is followed by that in the ischium, 

 and still later by that in the pubis. One epiphysis extends over the whole length of 

 the crest of the ilium ; a second covers the tuberosity of the ischium, passing forwards 



