158 CLINICAL VETERINARY MEDICINE AND SURGERY. 



and in both cases one or more arterial pulsations may be absent. 

 These troubles characterise both varieties of cardiac intermittency seen 

 in man by Laennec. In true intermittency it seems as though the 

 heart were really arrested for the moment, its contractions completely 

 ceasing. In false intermittency a certain number of cardiac cycles, 

 normal as regards strength, are followed by a feeble abortive contrac- 

 tion, which has no effect on the arteries, and which does not, therefore, 

 cause their walls to rise ; only the pulse is then really intermittent. 

 In both these varieties of intermittency, therefore, the regular cardiac 

 or arterial pulsation is merely interrupted, whilst in true irregularity 

 (arythmia) the pulsations are irregular or unequal, and the period of 

 the cardiac cycle is prolonged or shortened ; in intermittency the heart 

 usually beats normally save during the period of arrest. Both these 

 conditions may be found associated. 



I merely mention the false intermittencies usually seen during 

 diseases of the heart and of some other viscera. In patients showing 

 this condition the pulse is not only intermittent, but irregular, unequal, 

 and frequently almost imperceptible. 



In patients with true intermittency, auscultation of the heart reveals 

 a regular succession of orderly and equal beats, followed by a long 

 silence, coinciding with an abnormal prolonged rest of the heart, then 

 a new series of normal pulsations, to which succeeds a further silence, 

 and so on. Apart from these suspensions, which from time to time 

 and more or less periodically break the series, the heart acts regularly. 

 The frequence of the arrests varies greatly. Sometimes they are 

 separated by unequal periods of time, and are repeated every second, 

 third, tenth, twelfth, or fifteenth pulsation ; sometimes they succeed at 

 equal intervals, /. e. after the same number of pulsations, usually from 

 two to six. One sees horses in which the pauses are rhythmical to a 

 very remarkable degree ; in others the periodicity is subject to variation. 

 During the course of the day the same animal may at certain times 

 show regular, and at others irregular intermittency. In some rare 

 cases the series of pulsations are separated by long intermittencies, 

 which again are interrupted by a false beat. 



The duration of the arrests is generally in inverse proportion to the 

 number of pulsations in the series. It usually corresponds to one or 

 two cardiac cycles, though occasionally shorter or longer. In a case 

 mentioned by Siedamgrotzky the heart beat sixteen to twenty times 

 per minute, the beats occurring singly or in groups of two, three, or four, 

 separated by arrests corresponding in duration to two, three, or four 

 pulsations. At the post-mortem of this horse the heart was found 



