WINDPIPE TRACHEOTOMY. 143 



its own elasticity and that of the membrane at its base, and 

 more particularly the power of the hyo-epiglotideus muscle, 

 rises again and resumes its former situation. 



The Thyroid Cartilage (see 1, Fig. 3) occupies almost the 

 whole of the external part of the larynx, both anteriorly and 

 laterally. It envelops and protects all the rest. 



THE TRACHEA OR WINDPIPE. 



The windpipe is composed of an elastic cartilage, divided into 

 rings (50 or 52), sufficiently firm to resist ordinary pressure, and 

 united together by means of an interposed highly elastic fibro- 

 iigamentous substance, which, in efiect, constitutes a joint be- 

 tween each ring, giving the necessary flexibility to all its mo- 

 tions, and admitting of elongation when the head is stretched up- 

 ward or downward. 



It is indisputable that the windpipe should be prominent and 

 loose on the neck, in the horse from which active exertion is re- 

 quired, and which consequently is subjected to hurried respiration. 

 It is not commonly found thus in large slow beasts, like the cart- 

 horse, nor is it necessary. 



TRACHEOTOMY. 



It has been found that when obstructions, not speedily re- 

 movable enough for safety, occur in the windpipe of the horse, 

 a portion of the trachea may be safely removed, on or below the 

 point of obstruction, to admit of the continuance of respiration. 



The operation must be performed while the horse is standing, 

 and secured by a side-line, for he would, probably, be sulibcated 

 amidst the struggles with which he would resist the act of 

 throwing. The twitch is then firmly fixed on the muzzle ; the 

 operator stands on a stool or pail, by which means he can more 

 perfectly command the part, and an assistant holds a scalpel, a 

 bistoury, scissors, curvecf needles armed, and a moist sponge. 



The operator should once more examine the whole course of 

 the windpipe, and the difierent sounds which he will be able to 

 detect by the application of the ear, and likewise the difierent 

 degrees of temperature and of tenderness wliich the finger will 

 detect, will guide to the seat of the evil. 



The hair is to be closely cut oft^ from the part, the skin tight- 

 ened across the trachea with the thumb and fingers of the left 

 hand, and then a longitudinal incision cautiously made through 

 the skin, three inches in length. This is usually efiected when 

 there is no express indication to the contraiy on the fifth and 

 sixth rin^s ; a slip from which, and the connecting ligament 



