36 ROARING IN HORSES. 



the incision of the crico-thyroidean membrane 

 is completed from behind forwards, and from 

 within to without by holding the bistoury in 

 the position of a bow reversed. The vocal 

 cords are distinctly seen to turn outwards at 

 the moment of inspiration ; and it is at this 

 time that the opportunity should be taken to 

 incise the crico-thyroidean membrane up to 

 the body of the thyroid without damaging 

 the cords. The canula is then introduced 

 into the trachea, and immediately it is in 

 position an assistant, with the aid of the 

 india-rubber ball bellows, moderately distends 

 the elastic balloon attached to the tube. The 

 operator should determine to what extent it 

 is to be filled by passing the index and 

 middle fingers of the left hand into the 

 upper part of the trachea, or by feeling 

 the air reservoir of the bellows. When the 



