jb THE SURGICAL ANATOMY OF THE HORSE 



manner in which the animal carries its head should be taken into 

 consideration as it is generally advisable to conceal the tube from view as 

 much as possible, and yet insert it in such a position that there will be no 

 hindrance to the inward and outward passage of the respired air. An 

 advantage in adopting a seat high up the neck, is that, should complica- 

 tions subsequently arise which necessitate the re-insertion of the tube at 

 a different seat, a considerable area would be at the operator's disposal. 

 Such a complication is not by any means uncommon, for it is a matter of 

 frequent occurrence that the lumen of the trachea becomes almost 

 completely blocked at the position where the tube is inserted, on account 

 of the accumulation of granulation tissue, the result of irritation by 

 the tube. Many and various have been the designs of tubes which 

 have been claimed to prevent the growth of this tissue. 



Having selected the seat, the animal should be placed in stocks, 

 a longitudinal incision should be made along the median line about two 

 inches in length through the skin and panniculus, and the edges of the 

 wound well separated. It is then possible and advisable to separate the 

 riat pre-tracheal muscles by dissection, since it is not necessary to incise 

 any muscular tissue other than the panniculus, and consequently there 

 should be very little hemorrhage. The incision is made along the 

 median delicate raphe separating the sterno-thyro-hyoideii muscles. 

 Having done this the trachea is brought into view. 



A transverse incisi6n is now made between two of the cartilaginous 

 rings, and with a narrow-bladed scalpel a half-moon shaped piece should 

 be excised from each of the adjacent rings. About three-fourths of the 

 breadth of each ring should be taken, so that neither of the two rings is 

 completely severed. Whilst excising the pieces of cartilage they should 

 be firmly seized with a pair of rat-tooth forceps, otherwise there is a 

 danger that when separation is complete, they might slip away from the 

 operator and pass down the trachea. A circular hole is thus made 

 which is large enough to admit the ordinary sized tube. 



This operation is a simple one, and there is very little danger 



