DURATION OF THE MOVEMENT OF THE HEART. 113 



resonators and reinforce the heart-sounds, so that the latter often assume a 

 metallic, ringing character. Both the first and the second heart-sound may be 

 duplicated or split. Duplication of the first sound of the heart is explained by 

 failure of the tricuspid and mitral valves to contract at the same time. Some- 

 times a sound may be heard that is caused by the contraction of a well-developed 

 auricle and precedes the first sound like a presystolic murmur. As the closure of 

 the aortic valves does not coincide exactly with that of the pulmonary valves, 

 duplication or splitting of the second sound merely represents an exaggeration of 

 physiological conditions. All factors that cause acceleration in the closure of the 

 aortic valves such as ischemia of the left ventricle and retardation in the closure 

 of the pulmonary valves such as the presence of an excessive quantity of blood 

 in the right ventricle, and both' factors together when there is stenosis of the 

 left auriculo- ventricular orifice favor duplication of the second sound. 



When the valves of the heart are the seat of irregularities in association with 

 either stenosis or insufficiency, throwing the blood-stream into eddies or oscilla- 

 tions or producing friction, the heart-sounds are replaced by murmurs, that is, 

 sounds produced by the fluids and always associated with "circulatory disturb- 

 ances and the valvular changes referred to. It is rare for deposits and new-growths 

 projecting into the ventricle to give rise to murmurs in the absence of valvular 

 lesions or circulatory disturbances. Heart-murmurs are always associated with 

 the systole or diastole. As a rule, systolic murmurs are louder and more accentu- 

 ated than diastolic. Sometimes they are so loud that even the thorax is thrown 

 into vibration purring tremor. 



Diastolic murmurs always depend on structural changes in the mechanism of 

 the heart, such as insufficiency of the arterial valves or stenosis of the venous 

 orifices (usually on the left side only). Systolic murmurs are not always due to 

 disturbances of the cardiac mechanism. In the left heart systolic murmurs may 

 be caused by insufficiency of the mitral valve, stenosis at the aortic orifice and 

 by calcification or abnormal dilatation affecting the ascending aorta. Systolic 

 murmurs in the right heart, which are much more rare, are due to insufficiency 

 of the tricuspid valve or stenosis at the pulmonary orifice. 



Systolic murmurs are often present, although never so loud, in cases without 

 any valvular lesion, being caused by abnormal vibration of the valves or of the 

 walls of the arteries. They are heard most frequently at the pulmonary orifice, 

 next at the mitral, and more rarely at the aortic and tricuspid orifices. Anemia 

 and acute febrile affections are the causes of these murmurs. 



Heart-murmurs are sometimes produced by the friction of opposed roughened 

 surfaces of the inflamed pericardium (friction-murmurs) . The friction-sound may 

 be both audible and palpable. 



DURATION OF THE MOVEMENT OF THE HEART. 



The excised heart continues to beat independently for a time: in 

 cold-blooded animals for a long period, even for days, in warm- 

 blooded animals for a much shorter time. The last vestige of cardiac 

 action has, however, been observed in the rabbit after 15^ hours, in the 

 mouse after 46^ hours, in the dog after 96^ hours, and in a three-months- 

 old human embryo after 4 hours. The contraction of the excised heart 

 may be reinforced and accelerated by irritation. The contraction of the 

 ventricle first becomes enfeebled, and it is further observed that the 

 contraction of the auricle is not always followed by a ventricular systole, 

 two or more auricular contractions being succeeded by only one feebler 

 ventricular movement. The contractions of the ventricles, in addition 

 to being more infrequent, require a longer time for their completion, 

 and give the impression of being labored and sluggish (Fig. 30). Later, 

 the ventricles cease to contract altogether and only the auricles continue 

 to beat feebly. Direct irritation of the ventricles, however, as by a 

 prick, is followed by a single contraction. Still later the left auricle 

 ceases while the right auricle continues to beat, and it is the right 

 auricular appendage that continues to beat the longest, being accord- 

 ingly known to the ancients as "ultimum moriens." The same obser- 

 8 



