314 



BOVINE PATHOLOGY. 



length, is made througli the skin and muscle on to the 

 trachea, and the edges of the wound being held apart by 

 hooks, portions of two consecutive cartilaginous rings are 

 removed with a scalpel, so that a circular orifice extends 

 into the trachea large enough to admit the tracheotomy- 

 tube (see Fig. 60) ; the latter is then inserted and 

 retained by a band passing round the neck and attached 

 on each side of its plate (see Fig. 61). It must be 

 cleaned daily until, when a hand is kept over the orifice, 

 no impediment to breathing occurs. It must then be 

 permanently removed and the wound daily dressed with 

 carbolic glycerine until it closes. The opening in the 

 trachea becomes filled with fibrous substance or ossifi- 

 cation of the rings involved results. Care must be 

 taken lest the excised portions of cartilage fall into the 

 trachea. The operation may be performed on the animal 

 whether standing or lying. Sometimes it is supplanted 

 by Laryngotomy, which presents no special advantages 

 in the ox. It consists in perforation of the crico-thyroid 

 membrane, but the inferior position of the body of the 



Fig. 62. — Larynx and Os hyoides of the ox. a. Epiglottis. 

 extremity of long cornua. (Simonds.) 



h. Inferior 



thyroid in the ox is rather an impediment. Besides this, 

 the larynx in bovines is remarkable for its simplicity, 

 the absence of ventricles aud the high attachment of the 

 wide epiglottis, which has a rounded apex. The connec- 



