368 DR. C. F, SONNTAG ON THE ANATOMY, 



there is no centre of radiation as in Man. The following thickened 

 bands deserve mention: — (1) A strong band from the anterior 

 aspect of the base of the i-adial styloid to the trapezium and os 

 magnum ; (2) a weak external lateral ligament ; (3) a small internal 

 lateral ligament ; (4) a thickened band from the posterior part 

 of the distal radio-carpal joint to the back of the os magnum ; 

 (5) a posterior band from the distal part of the radius to the 

 cuneiform and unciform bones. Both anterior and posterior 

 ligaments are stronger than in Man. The cavity of the joint 

 (text- fig. 35 B) is complicated. The distal end of the radius is 

 divided into two facets, which articulate with the scaphoid and 

 semilunar bones. No articular fibi^o- cartilage lies on the distal 

 end of the ulna, but a very strong ligament runs from the distal 

 end of the ulna to the proximal end of the pisiform bone. It 

 plays over the outer aspect of the ulnar styloid, which is covered 

 with cartilage. The synovial cavity betAveen the radius and the 

 scaphoid and semilunar bones is prolonged into the inferior radio- 

 ulnar joint, over the ulnar styloid and ligament and upon the 

 surface of the cuneiform bone ; it gets in between the cuneiform 

 and pisiform. A large cavity separates the head of the os 

 magnum from the concave surfaces of the scaphoid and semi- 

 lunar bones, and it also separates the cuneiform and unciform. 

 It is continuous with the cavity between the scaphoid and trape- 

 zoid, A small ligament connects the scaphoid and os magnum 

 and divides the cavity partially into inner and outer parts. This 

 transverse carpal cavity is prolonged distally on either side of the 

 OS magnum. Two interosseous ligaments are also present in 

 the joint. A sesamoid bone lying on the apex of the pisiform is 

 separated from it by a synovial cavity and a strong interosseous 

 ligament. 



Gavpo-metacarpal Joint : — A continuous cavity extends along 

 the proximal ends of metacarpals 2-5. It is connected with the 

 transverse carpal cavity (text-fig. 35). Two interosseous liga- 

 ments run from the os magnum to the sides of the third meta- 

 carpal bone. In the intermetacarpal joints there are prolongations 

 of the carpo-raetacarpal synovial cavity, and interosseous liga- 

 ments connect the second to fifth metacarpals to one another. 

 The metacarpo-phalangeal joints are as in Man, but the dorsal 

 expansions of the extensor tendons can easily be separated from 

 the capsules. The inter-phalangeal joints are as in Man. Their 

 internal and external lateral ligaments are powerful. 



JPollical Joints: — A prolongation of the transverse carpal 

 cavity runs between the scaphoid and trapezium, and between 

 the trapezium and trapezoid, where there is also an imperfect 

 interosseous ligament. A strong ligament runs from the trape- 

 zium to the base of the index metacarpal. The carpo-metacarpal 

 capsule is complete ; it is thick and strong on its outer and pos- 

 terior aspects, but its inner and anterior aspects are weak. The 

 metacarpo-phalangeal and interphalangeal joints are as in Man, 

 and in the other digits of the Chimpanzee. 



