8 Feb., 1907.] 



Diseases of Farm Animals. 



73 



windpipe lies closest to the skin in that region. An incision about 3 inches 

 long is made in the skin lengthways, cutting right down on to the rings 

 of the windpipe. The opening may then be made by any of the following 

 methods (see Fig. 12): — 



{a) A square opening may be made by removing the parts of two 



contiguous rings ; or 

 {h) A longitudinal incision through se\eral rings may be made, 



sufficiently large to insert a tracheotomy tube ; 

 (c) A semi-circular incision in any two contiguous rings, whereby a 

 circular piece of the wall of the windpipe may be removed. 

 In both {a) and {c) methods care must be taken that the excised portion 

 shcmld not fall into the lumen of the windpipe. To avoid this, the part 

 to be removed should be firmly grasped with forceps during the operation. 



Fig- 13- — Tracheotomy tubes, {a) Ordinary tube to be secured in position by tapes. 

 [b] Self-retaining tube, {c) Ordinary tube in position. 



A specially constructed tube called a tracheotomy tube — (see Fig. 131^) 

 — is then inserted into the opening and kept in position by a mechanical 

 contrivance attached to it. The tube will require to be removed daily for 

 cleaning, and in order that the wound mav be dressed, until the edges are 

 healed. 



Tenotomy. 



This is an operation occasionally performed for the relief of contracted 

 tendons. It consists in the complete severance of the back tendons mid- 

 way between the fetlock and hock or knee, and results in their being 

 lengthened. Many months are required for the severed tendons to become 

 united by the interposition of false fibrous tissue. During this time the 

 foot should be shod with a shoe extended or thickened at the toe, and 

 lowered at the heels, so that the .severed ends may be kept as far apart 

 as possible. 



Trepanning or Trephining. 



This operation comprises the opening of hollow cavities in bones for the 

 removal of foreign bodies or accumulations of diseased products, such as 

 pus, parasites, or cvsts. It is seldom performed elsewhere than on the skull 

 or face. The opening is made with an instrument called a trephine — (see 

 Fig. 14) — which is really a tubular saw having a central point fixed in 

 the bone, by which the; sawing or cutting edge of the tube is steadied. 



