SINUS AND FISTULA 429 



The sinus, whether laid open or under-drained, should be dressed once 

 or twice, at an interval of two days, with undiluted carbolic acid or a 

 solution of chloride of zinc of the strength of 1 in 40, to be followed by 

 the daily application of iodoform and a covering of gauze and antiseptic 

 wool. Some practitioners plug old, obstinate sinuses with cotton -wool 

 dressed with perchloride of mercury and arsenic, and allow the dressing 

 to remain until the sinus is healed. 



Sinuses of recent formation may be found to yield to strong boracic 

 ointment and boracic lint as a dressing. 



Fistula is an unnatural canal or wound with an opening at one 

 extremity on the skin, and at the other into one or another of the various 



Fig. 424. Fistula of the Parotid Duct 



cavities or conduits of the body ; or it may extend between two cavities, as 

 between the bladder and the vagina vesico- vaginal fistula. 



Thus a wound in the wall of the abdomen may communicate with some 

 part of the intestine, or one in the cheek may have connection with the 

 parotid duct (fig. 424), through which faeculent matter in the one case and 

 saliva in the other may escape. It is the constant passage of these solids 

 and fluids through the canal, and the impossibility of rendering them 

 aseptic, which makes fistulous wounds so troublesome to heal. 



Treatment in these cases must be directed towards arresting the 

 outflow of the discharge and directing it into and along its proper 

 channel. Sealing over the outer orifice with collodion is in some cases 

 sufficient to bring about healing in fistula of parotid duct. In others 

 the surface of the fistula must be brought into a healthy condition by 

 antiseptic treatment to induce healing, or, if possible, laid freely open 



