INTRODUCTION 9 
bursa of the ligamentum nuche and by some 
writers as inflammation of the ligament itself. 
No one has thus far been able to prove its def- 
inite cause. Like fistula of the withers, ap- 
parently for want of an explanation based on 
demonstrable facts, it has always been attrib- 
uted to bruisings of the poll. 
While we do not entirely eliminate trauma- 
tism as the cause of some cases of poll-evil and 
some attacks of fistula of the withers, it has 
been our experience that when injuries are the 
cause, the wound or bruise is always apparent 
and the disease advances into the depths of the 
region by gradual stages from the initial focus 
deeper and deeper until the interior is finally 
attacked by the encroaching pyogenic process. 
In ordinary cases of both of these afflictions, 
the initial focus is always central, far down in 
the depths of the body where external violence 
can have but little influence. From this cen- 
tral location the disease as gradually advances 
in the outward direction in the ordinary case, 
as it does inward in the exceptional cases due 
to trauma. We have, therefore, no choice 
than that of describing both poll-evi] and fis- 
tula of the withers as having two distinct caus- 
es, one a wound or bruise at the very surface, 
and the other, and commonest, as yet unknown. 
The prevalence of fistula of the withers and 
