746 RESPIRATORY APPARATUS. 



TRACHEOTOMY. 



In bovine animals tracheotomy is only performed in urgent cases, 

 in order to ward off aspliyxia or to facilitate some other operation 

 on the upper air passages. It is performed exactly as in the horse, 

 the animal either standing or lying down. In the former case, the 

 animal may be placed in the trevis, but two strong assistants hold- 

 ing the animal's head and nose by means of "bulldogs" are often 

 sufficient. 



To prevent the animal from striking out with the front legs, a 

 rope is passed above and around the knees in the form of the figure 

 8 ; the animal is backed into a corner, and operation is then quite 

 safe. 



Large animals must be cast or placed in the trevis. 



The seat of operation should be washed, shaved, and disinfected. 



The operation may be divided into four stages. 



First stage. Vertical median incision about 2 inches long 

 through the skin at the height of the upper third of the trachea. 



Second stage. Separation with a blunt director of the muscles 

 covering the trachea. Incision through the pretracheal connective 

 tissue. 



Third stage. Circular or elliptical opening through the trachea 

 of a size corresponding to that of the tracheotomy tube. 



Fourth stage. Insertion of the tracheotomy tube. 



