THE BONES OF THE UPPER LIMB 



215 



border, the roughness being continued for a little on the palmar 

 aspect. This roughness, which is semilunar, is called the ungual 

 process, and it supports the nail and the tissues forming the pulp 

 of the finger. 

 The two phalanges of the thumb are of large size. 



Special Muscalar Attachments. — The base of the proximal phalanx of the 

 thumb gives insertion externally to the abductor poUicisand superficial head of 

 the flexor brevis pollicis, internally to the deep head of the flexor brevis pol- 

 licis, adductor obliquus pollicis, ' and adductor transversus poUicis, and 

 posteriorly to the extensor brevis pollicis. The base of the distal phalanx 

 gives insertion anteriorly to the flexor longus pollicis, and posteriorly to 

 the extensor longus pollicis. The base of the proximal phalanx of the index 

 finger gives partial insertion to the first dorsal interosseous externally, and the 

 first palmar interosseous internally. The base of the proximal phalanx of the 

 middle finger gives pjirtial insertion to the second dorsal interosseous ex- 

 ternally, and the third dorsal interosseous internally. The base of the proximal 



5th Year Year 6th Year 

 , ^ ; i 7th Year 



3rd Year /rr~^/ 5th Year 

 i2th 1 ear 



2nd Year .. 



. "^ Appear from the 3rd 

 ] to the 5th Year. 

 C .. J and join about 20 



Appears from the 3rd to the 5th Year, 

 and joins about 20 



Appear abottt the 9th Week 

 (intra-uterine) 



Fig. 128. — Ossification of the Bones of the Hand. 

 A, 2nd Metacarpal ; B, ist Metacarpal ; C, ist Phalanx. 



phalanx of the ring finger gives partial insertion to the second palmar inter- 

 osseous externally, and the fourth dorsal interosseous internally. The base of 

 the proximal phalanx of the little finger gives partial insertion to the third 

 palmar interosseous externally, and insertion to the abductor minimi digiti 

 (partially) and flexor brevis minimi digiti internally. 



The medullary foramen of each phalanx is situated on the palmar 

 aspect of the shaft, not far from the distal end. It may be single, 

 in which case it is mesially placed, or there may be two, one close 

 to each lateral border. In all cases the direction of the foramen 

 and the canal to which it leads is downwards towards the distal end. 

 The medullary arteries are furnished by the corresponding palmar 

 digital arteries. 



Structure. — The structure is that of a long bone. In the terminal 

 phalanges the medullary canal is replaced by cancellated tissue with 

 wide meshes. 



