TRACHEOTOMY. 165 



01 laceration. Theie are many beautiful points in the physiology ot the horse -which 

 deeerve much greater attention than has hitherto been paid to tliem. 



The windpipe should project from the neck. It should almost seem as if it were 

 detached from the neck, for two important reasons : first, that it may easily entei 

 Detween the channels of the jaw, so that the horse may be reined up without suffering 

 inconvenience ; and next, that being more loosely attached to the neck, it may more 

 readily adapt itself to the changes required than if it were enveloped by fat, or muscle 

 to a certain degree unyielding: therefore, in every well-formed neck and it will be 

 seen in the cut (p. 159) it is indispensable that the windpipe should be prominent 

 and loose on the neck. This is not required in the heavy cart-horse, and we do not 

 often find it, because he is not so much exposed to those circumstances which will 

 hurry respiration, and require an enlargement in the size of the principal air-tube. 



When the trachea arrives at the thorax, it suddenly alters its form, in order to adapt 

 Itself to the narrow triangular aperture through which it has to pass. It preserves the 

 game cartilaginous structure ; for if it has not the pressure of the external muscles, or 

 of accidental violence, to resist, it is exposed to the pressure of the lungs when they 

 are inflating, and it shares in the pressure of the diaphragm, and of the intercostal 

 muscles, in the act of expiration. Having entered the chest, it passes a little to the 

 right, leaving the oasophagus, or gullet, on the left; it separates from the dorsal ver- 

 tebrae ; it passes through the duplicating of the mediastinum to the base of the heart, 

 and it divides beneath the posterior aorta. Its divisions are called the bronchial tubes, 

 and have much to do with the well-being of the horse. 



Its rings remain as perfect as before, but a new portion of cartilage begins to pre- 

 sent itself: it may be traced as high as the tenth ring from the bottom; it spreads 

 over the union between the posterior terminations of the rings; it holds them in closer 

 and firmer connexion with each other; it discharges the duty of the transverse muscle, 

 which begins here to disappear, and the support of the cervical and dorsal vertebrae; 

 it prevents the separation of the rings when the trachea is distended ; it spreads down 

 upon, and defends the commencement of the bronchial tubes. Some other small plates 

 of cartilage reach a considerable way down the divisions of the bronchi, and the last 

 ring has a central triangular projection, which covers and defends the bifurcation of 

 the trachea. 



TRACHEOTOMY. 



The respiratory canal is occasionally obstructed, to an annoying and dangerous 

 degree. Polypi have been described as occupying the nostrils ; long tumours have 

 formed in them. Tumours of other kinds have pressed into the pharynx. The tumour 

 of strangles has, for a while, occupied the passage. The larynx has been distorted ; 

 the membrane of the windpipe, on the larynx, has been thickened, and ulcers have 

 formed in one or both, and have been so painful that the act of breathing was labo- 

 rious and torturing. In all these cases it has been anxiously inquired whether there 

 might not be established an artificial opening for the passage .of the air, when the 

 natural one could no longer be used ; and it has been ascertained that it is both a sim- 

 ple and safe operation, to excise a portion of the trachea, on or below the point of 

 obstruction. 



The operation must be performed while the horse is standing, and secured by a 

 side-line, for he would, probably, be suffocated 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 p:trt, 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 

 d fferent sounds which he will be able to detect by the application of the ear, and like- 

 wise the different degrees of temperature and of tenderness which the finger will detect, 

 will guide to the seat of the evil. 



The hair is to be closely cut off from the part, the skin tightened 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 

 ia no express indication to the contrary on the fifth and sixth rings ; a slip from which, 

 and the connecting ligament above and below, about half the width of eacii ring 1 , should 



