1892.] ^y* fCopc. 



Elboio of a Ilorse. 



I am informed by Dr. Werntz that the horse with disUicated elbow 

 lived for about two years after the accident, in the country, dying of 

 pneumonia. It used the leg (the left one) to a moderate degree, walking 

 on the extremity of the hoof, with the elbow everted. 



It results from the dislocation, that the internal part of the head of the 

 radius was in life without opposing humeral surface. The trochlear crest 

 of the humerus rotated inside of the median ridge of the head of the 

 radius ; and the interior roller of the humerus projected freely within the 

 internal border of the head of the radius. The external border of the 

 humeral condyles corresponds to the trochlear groove of the head of the 

 radius, which, of course, it docs not fill. Since the internal face of the 

 olecranar process rotates on the external epicondyle of the humerus, it 

 follows that the external face of the olecranar process has no contact and 

 was unused. 



The mechanical result of this position of the parts is as follows : The 

 internal side of the olecranar process develops friction on the external 

 surface of the external epicondyle of the humerus. The trochlear crest 

 of the humerus produces the same along the inner side of the median crest 

 of the head of the radius. The expansion of diameter of tlie internal 

 roller of the humerus produces friction on the internal edge of the head of 

 the radius. 



The structural result may be divided into two divisions : first, those 

 developed at points of contact of the parts thus abnormally brought 

 together, and second, those which appear at points abnormally sepa- 

 rated. 



Glass First. (1) A large new facet is developed on the posterosuperior 

 aspect of the external epicondyle of the humerus {la, Figs. 1 and 3), 

 which lies in an arc continuous with that of the external roller (or con- 

 dyle), and whose surface is directed downwards and outwards. It occu- 

 pies the usual position of the external flexor metacarpi muscular inser- 

 tion, which is in the normal humerus a truncate oval, looking down- 

 wards and backwards. This surface has been almost entirely removed, 

 Ihe posterior lace of the lateral rib of the humerus terminating below 

 in an obtuse acuraination, instead of the form described. The form of 

 the new facet is not entirely due to the planing down or absorption of 

 this region. The external eplcondylar fossa is filled with exostoses, of 

 which a large one in a superior position contributes material for the 

 inferior part of the new facet. The posterior rib of the humerus is also 

 exostosed so as to present a rough surlace of greater transverse extent 

 than in the normal humerus. This mass overhangs the new olecranar 

 fricet, forming a guide to its free extremity in rotation, the latter thus 

 running in an open groove. Thus is further luxation in a measure provi- 

 ded against. 



(2) The internal half of the humeral facet of the olecr.inar process is 

 narrowed, and its prominent internal rim rounded off; and it is con- 



