Cope. I ^ol) pec. 2. 



demonstrative of the truth of the doctrine of kinetogenesis. Two such 

 have recently come under my observation — both of them cases of disloca- 

 tion of the elbow joint. One of these is that of a man (No. 1838, Wistar 

 and Hornor Museum of the University of Pennsylvania), where the 

 cubitus is luxated backwards. The other is that of a horse, where the 

 cubitus is luxated outwards, which I owe to the kindness of Dr. William 

 B. Werntz, Vet., of Philadelphia. These specimens are especially 

 instructive as exhibiting the different effects of different luxations of the 

 same articulation. 



Elbow of Man. 



The human elbow, for which I am indebted to tlie authorities of the 

 University of Pennsylvania, is so dislocated as to liave allowed little 

 flexion and extension during life, but the radius retained rotary motion. 

 The humeral condyle rests on the ulna anterior to the coronoid process, 

 and the head of the radius is in contact with the posterior side of the 

 external epicondyle. It has resulted in consequence of the abnormal 

 position of the humerus, that a new coronoid process has developed as 

 far anterior to the true coronoid as the latter is anterior to the olecranon ; 

 and that a new humeral cotylus has appeared between the two coronoids 

 whose fundus is considerably elevated above that of the old one. In 

 consequence of the contact of the head of the radius, a deep cotylus has 

 been formed on the posterior face of the external epicondyle and adjacent 

 part of the condyle of the humerus, which is well adapted to the radial 

 head. From both of these new cotyli I removed a layer of articular 

 cartilage, and the osseous surface is as smooth and dense as those of 

 normal articulations. The edges of the cotyli are not as smooth as 

 those of the normal, but display the greater or lesser irregularities of 

 unfinished osseous deposit, except the internal border of the radial 

 cotylus of the humerus which is perfectly regular. 



Remarkable exostoses accompany the development of the cotyli. The 

 normal humeral cotylus of the ulna is partially filled with rough osseous 

 deposit. The internal epicondyle of the humerus sends a process down- 

 wards and posteriorly towards this cotylus, which it does not reach, but 

 projects freely. Tlie external epicondylar region develops three processes 

 of which the posterior and inferior anterior (distal) embrace the head of 

 the radius, forming the posterior and anterior boundaries of the radial 

 cotylus. Two ridges of exostosis of the shaft terminate at the posterior 

 process. The superior anterior process is short, and projects freely 

 distad. But a small portion of the condyle proper retains its articular 

 surface ; tliat is the posterior part of the internal condyle which articu- 

 lates with the ulna. The remaining surface of the condyles is concealed 

 by irregular bone deposits which quite obliterate its normal form, espe- 

 cially on the posterior (olecranar) surface, where the deposit is thickest 

 and most irregular. 



