196 



HEALTH AND DISEASE 



extends from the humerus above to the knee below. Its superior extremity 

 is divided into two concavities by a small ridge, and corresponds with the 

 two convexities and the dividing furrow observed on the lower extremity 



of the humerus, with which it ar- 

 ticulates to form the elbow -joint. 

 Behind, towards the outer side, it 

 presents a long roughened surface, 

 where it forms a bony union with 

 the ulna. 



The lower extremity is some- 

 what irregular, and articulates with 

 the four bones comprising the upper 

 row of the knee. In front there are 

 three grooves over which three ten- 

 dons play in passing down the limb 

 to their points of insertion. Each 

 tendon is supplied with a synovial 

 membrane to facilitate its move- 

 ments over the bone during flexion 

 and extension of the knee. 



Ulna (fig. 300). The ulna is a 

 long tapering bone, united by ossi- 

 fication to the outer and posterior 

 surface of the radius. Its superior 

 extremity is of considerable length 

 and thickness, and projects from the 

 head of the radius in an upward 

 and backward direction. This is the 

 elbow or olecranon process. In 

 front it presents a smooth surface, 

 which articulates with the groove 

 between the condyles of the humerus, 

 and also a hooked projection for- 



Fig. 301. Carpus 



1 Radius. 2 Pisiform. 3 Cuneiform. 4 Unciform. 

 8 Outer Small Metacarpal Bone. 8 Scaphoid. 7 Lunar. 

 8 Trapezoid. 8 Os Magnum. 10 Inner Small Meta- 

 carpal Bone. 11 Large Metacarpal Bone. 



ward termed the beak. 



CARPUS OR KNEE 



This (fig. 301) is the analogue of the wrist of man. It is made up of 

 seven, sometimes eight, small irregular bones arranged in two rows of 

 three each, one resting upon the other, with the seventh bone (pisiform) 

 situated at the posterior and outer part of the upper row. 



