FISTULA. 119 
‘tion, and the probing allow one to detect the exact nature of the existing 
lesion. The treatment varies according to cases. At times, simply a 
larger incision, and escharotic injections are all that is required; at 
‘others, to stimulate the action of the caustics and permit the free escape 
of the pus, one or several counter-openings have to be made, and 
drainage tubes inserted ; at other times, if the necrotic lesion is super- 
ficial, especially in cases of a bony alteration, it is better to dry off 
immediately the source of the suppuration by removal of the mortified 
part. Care should be taken that the pus be not in contact with tissues 
with sluggish nutrition, since they offer an easy prey to pyogenic 
microbes. Cauterization of the diseased center, a method borrowed 
from old hippiatria and brought down to our own times, is far inferior to 
immediate extirpation; it leaves an eschar, which sloughs off slowly ; 
and in fibrous tissues a new focus of necrosis may be the result of the 
extensive suppuration that follows. In horses and in cattle, sometimes, 
the product of the secretion of fistulous walls dries and forms in the 
tract a cylindrical, hollow, foreign body, which keeps up the suppura- 
tion. We have just seen a remarkable case of this nature in an 
animal suffering from an old fistula of the flank. 
Of serous fistula, some get well quite rapidly by the division of the 
tract and by simple antiseptic injections; those of serous bursa and 
small tendinous sheaths, belong to the same group. But fistulous 
tracts which open into large tendinous or articular synovial membranes 
are very serious in animals, on account of the difficulty of thoroughly 
‘disinfecting those cavities: in former days, injections of (Egyptiacum, 
a direct cauterization of the walls with a red iron or with nitrate of 
silver, were recommended for these. To-day antiseptic treatment is 
preferred. (See Articular Wounds and Arthritis.) Fistulze of the large 
‘serous membranes are very rare; they are observed only where the 
traumatisms which precede them have given rise to a circumscribed 
phlegmasia of these membranes and to the formation of adhesions which 
bound the suppurating serous territory. Antiseptics are used for these 
‘cases. Very recently, a strong carbolic acid solution has given us rapid 
recovery in a case of vagino-peritoneal fistula following an operation of 
-ovariotomy on a mare. 
We shall be concise in speaking of the treatment of mucous fistule, 
and will return to it when we study these lesionsin particular. Of these 
fistula, those which are kept up intentionally by a foreign body havea 
well-marked tendency to cicatrization. The muco-cutaneous fistula of 
the sinuses, following trephining, close in a few days by the removal of 
the corks or drains which keep them open; those of the trachea heat 
jn the same way when the tube of tracheotomy is taken away. If those 
‘that are due to dental caries or to suppurative alveolitis require a long 
time to heal after the extraction of the diseased tooth, it is due to the 
