THE HORSE IN SICKNESS AND DISEASE 321 



air and food, then, as we said in the first instance, form the 

 blood, the residue of unassimilated matter being expelled as 

 faeces. The blood thus supplied would soon over-nourish 

 the system, and occasion what is called 'plethora; but this 

 again has its escape in the excretories which throw off its 

 useless or redundant portions. 



The blood is the medium through which all this is 

 accomplished ; but we shall here merely look upon it in 

 connection with the organs which mechanically distribute 

 it, its vitiation embracing the whole range of diseases. 



The diseases of the heart divide themselves into three 

 classes : those affecting the substance of the heart ; those 

 of the surrounding membrane (pericardium) ; those of the 

 lining membrane, and of the valves and coats of the great 

 blood-vessels. 



INFLAMMATION OF THE HEART. 



The signs of heart-disease should be known, as the 

 animal so afflicted is a very risky investment. " He may 

 appear pleasing and even skittish," says Mayhew, " yet 

 his existence shall at any moment be cut short." 

 Auscultation is the surest means of detection. The 

 visible signs, however, are sometimes sufficiently emphatic 

 to admit of no doubt. The eye is expressive of anguish ; 

 the countenance is haggard ; the pulse irregular ; the 

 throbs of the heart visible ; and occasionally as visible 

 on the right side as on the left. The carotid artery can be 

 seen to pulsate in the neck. The regurgitation within the 

 jugular vein is nearly always excessive — it often reaches 

 almost to the jaw. It takes place by jerks, which ascend 

 higher and higher, each becoming smaller and weaker as it 

 mounts upward. The appetite is sometimes ravenous ; but 

 more often it is fastidious. The breathing is not acceler- 

 ated in any marked degree, which distinguishes heart- 

 disease from many other disorders. The animal suddenly 

 stops, trembles, and appears about to fall, but often as 

 suddenly recovers and proceeds upon the journey. Some- 

 times the horse will refuse to move, and is alwa^^s very 

 unwilling to turn in the stall. Occasionally he will open 

 his mouth as if yawning, and then heave a long-drawn 

 sigh. No peculiar symptom, however, can be specified as 

 heralding the final attack. Death is alwavs at hand, and 



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