140 DISEASES OF THE CIRCULATORY APPARATUS. 



but between the second and the next first the sound is much 

 greater. The first sound is a mixed muscular and valvular sound 

 of the mitrals and tricuspids, and the second is a semilunar 

 valvular sound. 



Unfortunately these sounds are indistinct and incomplete in the 

 dog, even in perfect health. In very fat dogs we may not hear 

 any heart-sound, or we may only hear the first one. In well-fed 

 dogs it is not rare to hear the first sound, which is a great deal 

 louder than the second, only on the left side. In thin animals 

 we can hear the sound distinctly on both sides. With the respira- 

 tory bruit we lose to a certain extent the full strength of the 

 sounds, and often only the first sound is heard. After great 

 activity the heart's action is increased so much that the sounds 

 follow each other so rapidly tliat it is impossible to distinguish one 

 from another. 



In pathological conditions the heart-sounds may be increased by 

 a number of causes, as in the beginning of certain fevers; but 

 generally it is an indication of hypertrophy. A les-ened heart- 

 sound is found in any heart-weakness, as in degeneration of the 

 heart-muscle, in accumulations of exudates arouud the heart in 

 the pericardium, or in emphysema of the lung-sections, etc. lu 

 such cases, as a rule, the heart-sound is imperceptible. 



As can be readily seen, it is by no means easy to hear the heart 

 beat in its normal condition, and the condition becomes more com- 

 plicated when we have to distinguish pathological sounds — " heart- 

 bruits." We distinguish between endocardial heart-bruits, which 

 originate in the heart direct, and pericardial heart-bruits, which 

 come from the arterial part of the heart and its envelope. The 

 former are divided into organic and inorganic bruits. The organic 

 heart-bruits are produced by stenosis (contraction) of the ring and 

 by insufficient or imperfect closing of the valves, which may occur 

 either in systole or diastole, making the heart-sound indistinct, or 

 it may be entirely absent, and the bruit takes the place of the 

 heart-sound. The systolic bruit is buzzing or blowing in charac- 

 ter, and indicates an imperfect closing of an arterio-ventricular 

 valve (in most cases of disease of the mitrals). The diastolic 

 bruit is rushing or wheezing in character, and indicates a stenosis 

 of the arterio-ventricular ostia, or the imperfect closure of an 

 arterial valve. The inorganic heart-bruit is seen in man in alL 



