XXIV.— CARDIAC INTERMITTENCY IN THE HORSE. 



For ten days past we have had in stable No. 6 a horse recovering 

 from pneumonia, in which the day after entry we discovered by 

 auscultation true cardiac intermittency, certainly of older standing 

 than the pulmonary disease. I called your attention to this patient, 

 and to the character of the intermittency. Allow me to-day to return 

 to this variety of cardiac disturbance, which is common in the horse, 

 but concerning which )ou will find very little in text-books and 

 periodicals. 



In a normal state, and under normal conditions, the heart beats 

 with perfect regularity. In an animal of any given species it contracts 

 the same number of times within the same period, though its sounds 

 are not invariably of one character. In the horse especially it is not 

 uncommon to find modifications in their intensity and tone, and a 

 tendency to doubling of one or other. To convince yourselves of 

 this, you have onl}^ to auscultate a number of the patients now under 

 treatment. 



The action of the heart is subject to an entire series of disturbances, 

 some common and ephemeral, others produced by change in the organ 

 itself, or in the nerves supplying it. The number of contractions may 

 be modified, increased, or diminished by many pathological states. 

 Sometimes the rhythm is slowed, a condition known as bradycardia ; 

 more frequently accelerated, tachycardia. Either of the two sounds 

 noted during each heart cycle may be doubled or replaced by a murmur. 

 The cardiac systole and the pulsations of the arteries may be of unequal 

 force. In all these cases the regularity of rhythm of the heart and of 

 the pulse are generall}- preserved, the pulsations succeeding one another 

 at equal intervals. 



But in some animals the cardiac systole and the arterial pulsations, 

 whether equal or unequal in force, no longer succeed one another 

 regularly. At more or less frequent intervals the heart's activity is 

 completely suspended for a short period, or the contractions are feeble, 



