w iiN utrirta — xitAutii:;uTum x . 



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 aU the rest. 



THE TRACHEA OR WINDPIPK 



The windpipe is composed of an elastic cartilage, divided into 

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

 united together by means of an iaterposed highly elastic fibro- 

 ligamentous 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 promment 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 w^ould, probably, "be suflbcated 

 amidst the struggles with which he would resist the act ot 

 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, curved needles armed, and a moist sponge. 



The operator should once more examine the whole course of 

 the windpipe, and the different sounds which he wiU be able to 

 detect by the application of the ear, and Ulcewise the different 

 degrees of temperature and of tenderness which the fingeir will 

 detect, will guide to the seat of the evil. 



The hair is to be closely cut off 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 effected when 

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

 sixth rings ; a slip from which, and the connecting ligament 



