184 CONTENTS OF THE CHEST. 



have more power in averting the consequences of aneurism than the human surgeon 

 possesses with regard to his patient. 



This will be the proper place to describe a little more fully the circulation of the 

 blood, and various circumstances connected with that most important process. 



THE ARTERIES. 



The vessels which carry the blood from the heart are called arteries {keeping air — 

 the ancients thought that they contained air). They are composed of three coats; 

 the outer or elastic is that by which they are enabled to yield to the gush of blood, and 

 enlarge their dimensions as it is forced along them, and by which also they contract 

 again as soon as the stream has passed ; the middle coat is a muscular one, by which 

 this contraction is more powerfully performed, and the blood urged on in its course; 

 the inner or membranous coat is the mere lining of the tube. 



This yielding of the artery to the gush of blood, forced into it by the contraction 

 of the heart, constitutes 



THE PULSE. 



The pulse is a very useful assistant to the practitioner of human medicine, and 

 much more so to the veterinary surgeon, whose patients cannot describe either the 

 seat or degree of ailment or pain. The number of pulsations in any artery will give 

 the number of the beatings of the heart, and so express the irritation of that organ, 

 and of the frame generally. In a state of health, the heart beats in a farmer's horse 

 about thirty-six times a minute. In the smaller, and in the thorough-bred horse, the 

 pulsations are forty or forty-two. This is said to be the standard pulse — the pulse 

 of health. It varies singularly littie in horses of the same size and breed, and where 

 it beats naturally there can be litt>e materially wrong. The most convenient place 

 to feel the pulse, is at the lower jaw (p. OS) a little behind the spot where the sub- 

 maxillary artery and vein, and the parotid duct, come from under the jaw. There 

 the number of pulsations will l)e easilj' counted, and the character of the pulse, a 

 matter of fully equal importance, will be clearly ascertained. Many horsemen put 

 the hand to the side. They can certainly count the pulse there, but they can do no- 

 thing more. We must be able to press the artery against some hard body, as the 

 jaw-bone, in order to ascertain the marner in w hich the blood flows through it, and 

 the quantity that flows. 



When the pulse reaches fifty or fift3'-five, some degree of fever may be apprehended, 

 and proper precaution should be taken. Seventy or seventy-five will indicate a dan- 

 gerous state, and put the owner and the surgeon not a little on the alert. Few horses 

 long survive a pulse of one hundred, for, by this excessive action, the energies of 

 nature are speedily worn out. 



Some things, however, should be taken into account in forming our conclusion from 

 the frequency of the pulse. Exercise, a warm stable, and fear, will wonderfully 

 increase the number of pulsations. 



When a careless, brutal fellow goes up to a horse, and speaks hastily to him, and 

 handles him roughly, he adds ten beats per minute to the pulse, and will often be 

 misled in the opinion he may form of the state of the animal. A judicious j^erson 

 will approach the patient gently, and pat and soothe him, and even then the circula- 

 tion, probably, will be a little disturbed. He should take the additional precaution 

 of noting the number and quality of the pulse, a second time, before he leaves the 

 animal. 



If a iiitick pulse indicate irritation and fever, a s/nu' pulse will likewise characterise 

 diseases of an opposite description. It accompanies the sleepy stage of staggers, and 

 every malady connected with deficiency of nervous energy. 



The heart may not only be excited to more frequent, but also to more violent action. 

 It may contract more powerfully upon the blood, which will be driven with greater 

 'orce through the arteries, and the expansion of the vessels will be oT<'ater and mom 

 sudden. Then we have the Jwrd pulse — the sure indicator of considerable fever, and 

 calling for the immediate and free use of the lancet. 



Sometimes the pulse may be hard and jerking, and yet small. The stream thourrh 

 forcible is not great. The heart is so irritable that it contracts before the ventricle 

 is properly filled. The practitioner knows that this indicates a dangerous state of 

 disease. It is an almost invariable accompaniment of inflammation of the bowels. 



