DISEASES OF HORSES 21 



border of the jawbone. The balls of the first and second or of the 

 second and third fingers should be pressed lightly on the skin over 

 this artery when its pulsations are to be studied. The normal pulse 

 of the healthy horse varies in frequency as follows : 



Stallion 28 to 32 beats per minute. 



Gelding 33 to 38 beats per minute. 



Mare 34 to 40 beats per minute. 



Foal 2 to 3 years old 40 to 50 beats per minute. 



Foal 6 to 12 months old 45 to 60 beats per minute. 



Foal 2 to 4 weeks old 70 to 90 beats per minute. 



The pulse is accelerated by the digestion of rich food, by hot 

 weather, exercise, and. excitement. It is slightly more rapid in the 

 evening than it is in the morning. Well-bred horses have a slightly 

 more rapid pulse than sluggish, cold-blooded horses. The pulse 

 should be regular ; that is, the separate beats should follow each other 

 after intervals of equal length, and the beats should be of equal full- 

 ness, or volume. 



In disease, the pulse may become slower or more rapid than in 

 health. Slowing of the pulse may be caused by old age, great exhaus- 

 tion, or excessive cold. It may be due to depression of the central 

 nervous system, as in dumminess, or be the result of the administra- 

 tion of drugs, such as digitalis or strophantus. A rapid pulse is 

 almost always found in fever, and the more severe the infection and 

 the weaker the heart the more rapid is the pulse. Under these condi- 

 tions, the beats may rise to 80, 90, or even 120 per minute. When 

 the pulse is above 100 per minute the outlook for recovery is not 

 promising, and especially if this symptom accompanies high tempera- 

 ture or occurs late in an infectious disease. In nearly all of the dis- 

 eases of the heart and in anemia the pulse becomes rapid. 



The pulse is irregular in diseases of the heart, and especially 

 where the valves are affected. The irregularity may consist in vary- 

 ing intervals between the beats or the dropping of one or more beats 

 at regular or irregular intervals. The latter condition sometimes 

 occurs in chronic diseases of the brain. The pulse is said to be weak, 

 or soft, when the beats are indistinct, because little blood is forced 

 through the artery by each contraction of the heart. This condition 

 occurs when there is a constriction of the vessels leading from the 

 heart and it occurs in certain infectious diseases, and is an indication 

 of heart weakness. 



In examining the heart itself it is necessary to recall that it lies 

 in the anterior portion of the chest slightly to the left of the median 

 line and that it extends from the third to the sixth rib. It extends 

 almost to the breastbone, and a little more than half of the distance 

 between the breastbone and the backbone. In contracting, it rotates 

 slightly on its axis, so that the point of the heart, which lies below, is 

 pressed against the left chest wall at a place immediately above the 

 point of the elbow. 



If the horse is not too fat, one may feel the impact of the apex of 

 the heart against the chest wall with each contraction of the heart by 

 placing the hand on the left side back of the fifth rib and above the 



