152 THE HORSE. 



back part of the mouth, forced against the soft palate, which giving^, way, and 

 being raised upwards towards the 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, ex- 

 cept in extreme cases, the act of vomiting in the horse. Whatever is re- 

 turned 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 

 nconvenience and danger might result ; therefore, this opening is not only 

 ined 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 apertiu'e. 

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

 flat on the entrance into the windpipe, and prevents the possibility of any 

 thing 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 the 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 the 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. 



THE ANATOMY AND DISEASES OF THE NECK AND NEIGHBOURING 



PARTS. 



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

 inalia, except one species, is composed of seven bones, called vcrtebrce, 

 moveable or turning upon each other (see cut, p. 63). 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 scull is called the atlas, (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 projec- 

 tions sideway ; but without the sharp and irregular processes which are 

 found on all the others. The pack-wctjCj or ligament, by which the head 

 is principally supported (f, 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 



