MITRAL INSUFFICIENCY IN THE HORSE. I37 



The two principal signs of mitral insufficiency are a systolic 

 murmur and feebleness and small size of the pulse. On auscultat- 

 ing the heart one hears a murmur commencing with systole, covering 

 the short pause, and ending with the second sound ; the latter and the 

 long pause are usually normal. This murmur may extend not only 

 over the base, centre, and apex of the heart, but over a considerable 

 area of the surrounding parts. It is clearly a mistake to say that it is 

 heard most loudly over the apex. Being due to reflux of blood from 

 the left ventricle into the auricle, it is produced in the auriculo- 

 ventricular opening, which is situated about one and a quarter inches 

 below the aortic orifice, and about six to eight inches from the apex. 

 The point of maximum intensity corresponds to the depression 

 in the left pulmonary lobe, or to the mesocardiac zone. Like 

 the aortic murmur, it varies greatly in strength and tone, depending 

 on the degree of insufficiency and on the existence or absence of 

 vegetations on the valvular flaps. The configuration of the margins of 

 the valve changes as the process develops, and the character of the 

 murmur may thus undergo modification at uncertain intervals. In 

 one horse which I kept under observation the sound was at first soft, 

 afterwards harder and vibrating. As in the case of diastolic murmurs, 

 the modification in character of systolic murmurs bears no relation to 

 the changes in the valvular condition as determined by post-mortem 

 examination. All one can say is that soft murmurs usually denote 

 either trifling or very large insufficiencies, and rough strong murmurs 

 insufficiencies of moderate extent. 



The pulse of mitral insufficiency contrasts with that of aortic 

 insufficiency. Whilst in the latter the pulsations are strong and 

 bounding, in the former they are feeble, often almost indistinguishable 

 or uncountable. At the moment of ventricular contraction one 

 portion of the blood contained in the left ventricle escapes by the 

 mitral orifice ; only a small wave enters the aorta, scarcely lifting the 

 arterial wall, and the pulse is invariably small. For a long time no 

 other change is apparent ; but when the valvular lesion has reacted on 

 the heart muscle a want of rhythm becomes apparent ; the cardiac 

 contractions and the pulse at first become unequal ; later, inter- 

 mittences occur, alternating with the series of normal heart-beats. In 

 one ot the patients of which I have spoken disturbance of the circula- 

 tion could be detected, pointing to change in the heart muscle or to a 

 cardiac complication of the mitral disease. 



The other symptoms which occur result from stasis of blood in the 

 viscera. Passive congestion of the lung produces oppression, dyspnoea, 

 cough, and later bronchorrhcea. In some subjects reflex disturbance 



