118 VETERINARY SURGICAL THERAPEUTICS. 
tends far beyond the fistulous tract, or perhaps pressure cannot be 
applied. In such cases, the rule is to make a counter-opening in the 
most dependent part so as to allow and complete the escape of the 
pus through a drain tube. Whether there is undermining or not, if the- 
fistulous tract is old, organized, and lined with an epithelial layer, cica- 
trization cannot take place without destroying this superficial covering: 
and stimulating an active granulating process. Injections, the seton 
and cauterization fulfil all these requirements. A great number of 
therapeutic agents have been used in injections to stimulate the granu-- 
lation of fistula; among them metallic sulphates, tinctures and anti-- 
septics in concentrated solutions. The most desirable of these are the- 
Villate solution, the tincture of iodine, the alcoholic solution of corrosive- 
sublimate, the aqueous solution of chloride of zinc (8-10 %) and of car-. 
bolic acid (5%). If cicatrization is slow, it is wise to change the injec-~ 
tions. In cases where these fail, solid caustics may be introduced into. 
the fistula: minium troches, pencils of nitrate of silver, paste of sub- 
limate or of chloride of zinc. With obstinate bicutaneous fistule, the- 
introduction into the tract of tents or small setons, impregnated with 
irrigating caustic or vesicating preparations (Villate solution, tincture 
of iodine, spirits of turpentine, blister ointment, basilicon, or iodide of 
mercury ointment), is good practise ; when it is necessary to introduce- 
several tents, they should be made small, so as to not interfere with the 
granulations. Cauterization of the tract of old fistula with the hot. 
iron is an old, severe, but certain mode of treatment. It is done with. 
a blunt probe or a metallic wire of small dimensions; the narrow and 
blunt point of the zoocautery is very good for short tracts. In some- 
cases, it is advantageous to have recourse to incision, and curetting- 
of the tract. Incision assists cicatrization of fistulae with several. 
tracts. The callosities existing on the walls of old fistulous canals gen-- 
erally require to be removed with the bistoury or with the curette. 
Some of these fistula require special operations; for instance, that. 
which is present in cases of keraphyllocele, is relieved only by the ex-- 
tirpation of the horny growth. 
The treatment of symptomatic fistule depends on their causes, and’ 
the conditions of their presence. Some are due to the presence of a 
foreign body or a necrosed, loose piece of bone; they are recognized’ 
by the pus which flows from them, not very abundant, or unpleasant. 
in nature. They heal rapidly after that which causes them is removed.. 
To do this, one has only to enlarge the size of the tract, take hold of 
the irritating object and extract it. Most of these fistule are the- 
expression of a necrotic lesion involving a bone, a cartilage, a tendon, 
a ligament or an aponeurosis; they secrete abundantly a grayish,. 
watery pus, often grumous and carrying small pieces of necrosed. 
structure. Generally, the seat of the wound, the extent of the indura~ 
