THE METACAEPUS. 223 



four points the transverse carpal ligament is attached, which stretches across from 



side to side, and thus 

 converts the furrow into 

 a canal through which the 

 flexor tendons pass to reach 



V. Metacarpal^ ^ \~^$JJSB . ^~~^ -J v - Metacarpal the fingers. 



/Capitate bone 



Os lunatuin 



FIG. 220. THE EIGHT Os HAMATUM. 



NOTE. The bone is represented in the centre of the figure in the position 

 which it occupies in the right hand viewed from the volar aspect. 

 The views on either side, and above and below, represent respectively 

 the corresponding surfaces of the bone turned towards the reader. 



FIG. 221. RADIOGRAPH OP THE 

 HAND AT BIRTH. 



It will be noticed that whilst the 

 primary centres for the metacarpus 

 and phalanges are well ossified, the 

 carpus is still entirely cartilaginous. 



Compare this with the tarsus at 

 birth, in which the tarsus is shown 

 in part already ossified. 



Ossification. At birth the carpus is entirely cartilaginous. An exceptional case is 

 figured by Lambertz, in which the centres for the capitate and triquetral bones were already 

 present. The same authority states that it is not uncommon to meet with these centres 

 in the second month after birth. According to Debierre (Journ. de VAnat. et de la 

 Physiol. vol. xxii. 1886, p. 285), ossification takes place approximately as follows : 



Capitate bone . 



Os hamatum 



Os triquetrum . 



Os lunatum 



Greater multangular. 



Navicular 



Lesser multangular . 



Pisiform . 



11 to 12 months. 



12 to 14 months. 

 3 years. 



5 to 6 years. 



6 years. 

 6 years. 



6 to 7 years. 

 10 to 12 years. 



The same observer failed to note the appearance of a separate centre for the hamulus 

 of the os hamatum, and records the occurrence of two centres for the pisiform. 



The Metacarpus. 



The metacarpal bones form the skeleton of the palm, articulating proximally 

 with the carpus, whilst by their distal extremities or heads they support the bones 

 of the digits. Five in number, one for each digit, they lie side by side and 

 slightly divergent from each other, being separated by intervals, termed interosseous 

 spaces. Distinguished numerically from the lateral to the medial side, they all 

 display certain common characters ; each possesses a body or shaft, a base or carpal 

 extremity, and a head or phalangeal end. 



The bodies, which are slightly curved towards the volar aspect, are narrowest 

 towards their middle. The dorsal surface of each is marked by'two divergent lines 

 which pass distally from the dorsum of the base to tubercles on either side of the 



