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 vertebra 
mesially and to the distal border of the secapu- 
