350 DISEASES OF THE HORSE’S FOOT 
explored with the probe and a. knowledge of its exact 
dimensions arrived at. This is carefully noted, and the 
horn of the wall for some little distance around it then 
rasped down quite thin. Immediately over the sinus, and 
for a short distance on either side of it, the horn is stripped 
away to the sensitive structures. The cavity of the fistula 
is then opened up with a scalpel, and every particle of 
diseased tissue removed with this instrument and a pair 
of forceps. After-dressing consists simply in the application 
of suitable antiseptics. 
When the Complication of Necrosed Tendon or Ligament 
exists. —We may take it as an axiom that wherever this 
exists, whether it is in the extensor pedis, in the lateral 
ligaments of the joint, or in portions of the flexors, all 
diseased structures should, where possible, be removed. This 
is done either with a scalpel or with a curette. 
When septic matter has gained the sheath of the perforans, 
and the formation of pus therein is indicated by inflam- 
matory swellings in the hollow of the heel, it is sometimes 
advisable to lay the sheath open for 1 to 2 inches along the 
course of the tendons. This, if a fistula is present, may be 
best done with a blunt-pointed bistoury, or with a cannulated 
director and a scalpel. With the pus thus given exit, and 
an antiseptic dressing regularly applied, the case sometimes 
ends in rapid resolution. More often than not, however, it 
is found that the pus has been liberated too late, and that 
it has gravitated in the sheath to the extent of affecting the 
plantar aponeurosis. Or it may be, of course, that it was in 
the plantar aponeurosis the disease commenced. Whichever 
may have been the case, we have in the hollow of the heel 
one or more fistulous openings, or an opening we have made 
ourselves, leading down to a necrosed portion of the terminal 
expansion of the perforans. 
In such cases we ourselves have derived benefit from a 
regular flushing of the sinuses with a 1 in 2,000 solution 
of perchloride of mercury, introduced by means of a glass 
syringe, followed later by flushing in the same manner with 
a1 in 40 solution of carbolic acid, the hollow of the heel 
