14 FISTULA AND POLL-EVIL 



withers, muscular withers, effaced withers, 

 prominent withers, each of which, in addition 

 to being descriptive in the study of profile, is 

 equally suggestive in the study of etiology of 

 affections of these parts and their surgical 

 treatment. Each one of these characteristics 

 contributes to a different etiologic factor as 

 well as a different surgical problem. 



Boundaries 



The withers, although having ill-defined lim- 

 its, may be said, for surgical study, to extend 

 from the crest of the neck anteriorly, to a point 

 posteriorly, where the dorsal spines descend to 

 the level of the back. The second dorsal spine 

 may be selected as the uniform anterior limit, 

 but posteriorly no line can be drawn, because 

 some withers end abruptly toward the level 

 of the back, while others slope gradually to a 

 more distant posterior point between the eighth 

 and twelfth spines. The highest point is al- 

 most universally at the fifth spine. The second 

 dorsal spine may, therefore, be said to repre- 

 sent the anterior boundary, the fifth spine the 

 summit and any point between the eighth and 

 twelfth dorsal spines the posterior boundary. 

 In the downward direction, the withers may be 

 said to descend to the bodies of the vertebrae 

 mesially and to the distal border of the scapu- 



