152 



THE HORSE. 



Dack part of the mouth, forcpd af^ainst the soft palate, which, giving way, 

 and being raised upwards towards tlie entrance into the nose, prevents the 

 food from going that way. It passes to the pharynx ; and the soft palate, 

 falling down again, prevents its return to the mouth, and prevents likewise, 

 except in extreme cases, the act of vomiting in the horse. Whatever is 

 returned from the stomach of the horse, passes through the nose, as the cut 

 will make evident. 



The sides of the pharynx are lined with muscles, which now begin power^ 

 fully to contract, and by that contraction the bolus is forced in until it 

 reaches the gullet (10), which is the termination of the pharynx. Before, 

 however, the food reaches the gullet, it has to pass over the entrance into 

 the windpipe (3) ; and should any portion of it enter into that tube, much 

 inconvenience and danger might result : therefore this opening is not only 

 lined by muscles by which it may be closed at the pleasure of the animal, 

 but it is likewise covered by a heart-like elastic cartilage, the epiglottis (2), 

 with its back towards the pharynx and its hollow towards the aperture. 

 The epiglottis yields to the pressure of the bolus passing over it, and lies 

 Hat on the entrance into the v.indpipe, and prevents the possibility of any 

 tiling entering into it ; and no sooner has the food passed over it, than it 

 rises again by its own elasticity, and leaves the upper part of tlie wind- 

 pipe once more open for the purpose of breathing. The voice of animals 

 is produced by the passage of air through this aperture, communicating 

 certain vibrations to folds of tiie membrane covering the part, and these 

 vibrations are afterwards modified in their passage through the cavities of 

 the nose. To understand the diseases of these parts, we must consider 

 the anatomy of the neck generally. 



CHAPTER IX, 



ANATOMY AND DISEASES OF THE NECK AND ADJACENT PARTS. 



The neck of the horse and of every animal belonging to the class main- 

 malia, except one species, is composed of seven bones, called vertebnr, 

 moveable or turning upon each other (see cut, p. 63 V They are connected 

 together by strong ligaments, and form so many distinct joints, in order to 

 give sufficiently extensive motion to this important part of the body. The 

 bone nearest to the skull is called the alJas, (see cut, p. 63, and g, p. 68,) 

 because, in the human being, it supports the head. In the horse, the head 

 is suspended from it : it is a mere ring-shaped bone, with broad projections 

 sideway ; but without the sharp and irregular processes which are found on 

 all the others. The pack-7vax, or ligament by which the head is principally 

 supported, (/, p. 68,) and which is strongly connected with all the other 

 bones, passes over this without touching it, by which means the head is 

 much more easily and extensively moved. The junction of the atlas with 

 the head is the seat of a very serious and troublesome ulcer, termed 



POLL-EVIL. 



From the horse rubbing and sometimes striking his poll against the 

 lower edge of the manger, or hanging back in the stall, and bruising the 



