The Region of the Shoulder. 27 



of the joint around the biceps tendon, which extension of 

 synovial membrane reaches down the arm to a point 

 about half an inch below the lower facet of the greater 

 tub^rosity. The swelling around this tendon is said to be 

 bilobed, but the tendon does not lie in the middle of the 

 prominence, rather to the outer side of it. 



Dislocation at the Shoulder Joint. The 

 large head of the humerus, articulating with the shallow 

 glenoid surface an arrangement whereby the greatest 

 amount of freedom is secured to the joint really proves 

 a source of weakness, as far as protection from dislocation 

 is concerned. Besides, the joint is not strengthened by 

 powerful ligaments as is the sterno-clavicular articulation,, 

 nor is it dependent for strength on bony interlocking as 

 in the elbow joint, but relies for its integrity mainly on the 

 muscles. These muscles are really elastic ligaments, 

 though they differ from the latter in that they may be 

 taken by surprise, as from unexpected strain, etc., hence 

 it follows that a sudden, severe wrench, especially in cer- 

 tain positions of the arm, may cause displacement of the 

 head of the bone. It is true that the overhanging arch 

 composed of acromion, coracoid and the ligament joining 

 them does, to some extent, strengthen the upper part of 

 the joint, yet the muscles surrounding the articulation are 

 its chief means of protection. There is, however, a por- 

 tion of the capsule, its lower and anterior part, between 

 the triceps, behind, and the subscapularis, in front, that is 

 unsupported by muscles, and not only is this part unsup- 

 ported, but is itself weak as compared with the rest of 

 the capsule, since the coraco-humeral ligament strength- 

 ens the upper part of the capsule, and Flood's accessory 

 band, the front part, and Schlemm's accessory ligament, 

 the under part ; so that, between the last two bands there 

 is an unprotected portion of 'the capsule, and, it is on this 



