TRACHEOTOMY. 



453 



now incised either perpendicularly through the third and fourth 

 rings, or horizontally in the intervening ligament ; or a vertical 

 incision providing more room is made by thrusting the knife, 

 with the cutting edge upwards, into the trachea at the lower 

 edge of the wound, and carrying the cut upwards through two or 

 three tracheal rings (Fig. 356). Hooks are now applied to the trachea, 

 or the index and middle fingers of the left hand hold the edges of 

 the wound apart, and the cannula is inserted. The trachea in the 

 horse being of considerable size, little difficulty is met with, even 

 when dealing with the hard cartilages of old subjects. 



When the cannula is to be worn for a considerable period or 

 permanently, and must, therefore, be removed at intervals to be 

 cleaned, a round, oval, or occasionally a 

 square piece is excised from the anterior 

 wall of the air-tube. Viborg, who first re- 

 commended the square opening (Fig. 356, a), 

 directs the knife to be inserted between 

 two cartilages, and a horizontal cut made 

 about | inch in length. This cut should 

 extend an equal distance on either side of 

 the middle line. From each of its ends a 

 vertical cut is next made downwards, and 

 the piece of cartilage which now hangs 

 by the intercartilaginous band below is 

 grasped with dissecting forceps and cut 

 away, care being taken to prevent it falling 

 into the trachea. The cannula is then 

 placed in position. Lafosse, Brogniez, and 



Gunther have expressed themselves in favour of the oval opening, 

 which may be produced by first dividing the intercartilaginous 

 ligament and then excising a half-round piece from the cartilages 

 above and below, without, however, quite dividing these (Fig. 356, c). 

 Bending of the rings and stenosis of the trachea, which result from 

 completely cutting through the cartilages, are thus avoided. 

 Brogniez's tracheotome likewise produces an oval cut, but can be 

 replaced by a bistoury, deftly manipulated. The same remark 

 applies to other instruments, such as Marty's tracheotome, which 

 removes a circular piece from the two cartilaginous rings, like a 

 trephine. The tracheotome introduced by Mr. McKenny, of Dublin, 

 is simple in action and very efficient ; it cuts a circular opening 

 large enough to accommodate a Jones' tube. 



Tracheotomy is one of the simpler of equine operations, and is 



Fig 357.— Barthelemy's 

 cannula. 



