KINE TO GENESIS. 279 



process with the epicondyle, which has developed a 

 considerable articular face, on which movement takes 

 place in extension and flexion. The posterior border 

 of this face has developed a ridge which borders the 

 facet behind, and retains the olecranon in place. Two 

 other facets are developed on the humeral condyles, 

 and two on the head of the radius. The most impor- 

 tant of the latter is a bevel of the external part of the 

 surface to the border, due to the contact of the ex- 

 panded internal humeral condyle. The articular face 

 of the olecranon is much depressed in consequence of 

 its articulation with the external epicondyle of the 

 humerus. Besides these new and changed facets, the 

 effect of the luxation is seen in the development of os- 

 seous crests at the points of insertion of the articular 

 ligaments. One of these on the humerus has been al- 

 ready referred to. Another is concentric with and 

 posterior to the internal humeral facet of the olecranar 

 process, and serves as a guide to the humeral crest 

 above described. A third is an extensive osseous de- 

 posit on the internal face of the head of the radius, 

 which partially builds an extension of the head of the 

 radius, which if completed would articulate with the 

 overhanging portion of the internal humeral condyle. 

 A third modification of normal structure is similar to 

 that observed in the human elbow. It consists of os- 

 seous deposit beneath the synovial bursa at points 

 where the luxation causes a gaping of the surfaces. 

 This occurs at the trochlear groove of the head of the 

 radius, which is partially filled up with exostosis. 



The preceding observations lead to the following 

 conclusions : 



First. Continued excessive friction removes osse- 

 ous tissue from the points of contact until complete 



