274 HUMAN ANATOMY. 



is the narrowest portion of the bone, and much more Hkely to be broken across, 

 detaching one or other portion of bone rather than the whole epiphysis separating 

 at this age" (Poland). 



As the synovial membrane is attached on the inner side about five millimetres 

 (three-sixteenths of an inch) below the internal epicondyle, fracture of the latter 

 does not necessarily extend into the joint-cavity. On the outer side it is attached 

 up to the level of the external epicondyle, so that the joint is likely to be involved 

 in traumatic separation of that process. 



As the capsule of the joint is attached at a higher level than the epiphysis in 

 front, behind, and laterally, the displacement in epiphyseal separations is within the 

 capsule, and therefore likely to be limited. The close relationship of the synovial, 

 membrane gives rise, however, to extensive effusion, which affects both diagnosis 

 and treatment. 



The union to the diaphysis at about the fifteenth year leaves the further growth 

 of the bone dependent upon the upper epiphysis (page 272) ; hence injuries involving 

 the epiphysis, or excision of the elbow in which the epiphyseal limits are overstepped, 

 will not be followed by arrest of growth if the patient is more than fifteen years of 

 age. 



Epiphysitis, on account of the synovial and capsular relations above described, 

 is apt to involve the elbow-joint, and to result in considerable stiffness. 



The anatomical deformity and diagnosis of epiphyseal separation will be con- 

 sidered in connection with the subjects of supracondylar fracture and luxation of the 

 elbow (page 590). 



About two inches above the inner condyle there is often found (one per cent, 

 of recent skeletons, Turner) a hook-like process projecting downward and converted 

 into a foramen by a ligamentous band. When it is present the median nerve 

 usually passes through it, which demonstrates that " it is the homologue and rudi- 

 ment of the supracondyloid foramen of the lower animals" (Darwin). The process 

 can sometimes be recognized by the sense of touch. The intercondylar foramen, 

 which is occasionally present in man, occurs, but not constantly, in various anthro- 

 poid apes, and, though it weakens the bone somewhat, is chiefly interesting because 

 it is found in much greater frequency in skeletons of ancient times, and thus illus- 

 trates Darwin's assertion that "ancient races more frequently present structures 

 which resemble those of the lower animals than do modern." 



THE SHOULDER-JOINT. 



The ligaments of this articulation are : 



Capsular ; Glenoid 



Accessory ligaments : 



Coraco-Humeral ; Gleno-Humeral. 



This is a very simple instance of the ball-and-socket joint, the only irregularity 

 being the position of the humeral head somewhat on one side instead of at the top 

 of the bone, so that the axis of rotation does not correspond with the axis of the 

 shaft. 



The shallow socket of the glenoid cavity, lined with articular cartilage, is 

 deepened by the glenoid ligament' (Figs. 290, 292), a fibro-cartilaginous band 

 attached by its base to the border of the cavity and ending in a sharp edge. It is 

 thus triangular on section (Fig. 291), the breadth of the base being five millimetres 

 and the height at its greatest about one centimetre. This ligament is composed 

 chiefly of fibres running around the socket. It is directly continuous with the fibres 

 of the long head of the biceps from the insertion of the latter into the top of the 

 socket. 



The capsular ligament (Fig. 289) is so lax that in the dissected joint the 

 head of the humerus falls away from the socket. In life it is kept in place chiefly 

 by the tonicity of the surrounding muscles. The course of the fibres is in the main 

 longitudinal, but they are indistinct. The capsule arises above from the edge of the 



' Labrum glenoidale. ~ Capsula artirularis. 



