74 



DURATION OF THE MOVEMENTS OF THE HEART. 



If a pathological cavity, filled with air, be so placed, and of such a form as to act 

 r to the heart-sounds, they may assume a "metallic" character. The first and 



"impure, 

 as a resonator 



second sounds may be "reduplicated "or [although "duplication" is a more accurate term 

 (Barr)] doubled. The reduplication of the first sound is explained by the tension of the 

 tricuspid and that of the mitral valves not occurring simultaneously. Sometimes in disease a 

 sound is produced by a hypertrophied auricle producing an audible presystolic sound, i.e., a 

 sound or "murmur," preceding the first sound. [This has been questioned quite recently.] 

 As the aortic and pulmonary valves do not close quite simultaneously, a reduplicated second sound 

 is only an increase of a physiological condition. All conditions which cause the aortic valves 

 to close rapidly (diminished amount of blood in the left ventricle) and the pulmonary valves to 

 close later (congestion of the right ventricle both conditions together in mitral stenosis), 

 favour the production of a reduplicated second sound. 



Cardiac Murmurs. If irregularities occur in the valves, either in cases of stenosis or in 

 insufficiency, so that the blood is subjected to vibratory oscillations and friction, then, instead 

 of the heart-sounds, other sounds murmurs or bruits arise or accompany these. A combina- 

 tion of these sounds is always accompanied by disturbances of the circulation. [These murmurs 

 may be produced within the heart, when they are termed endocardial ; or outside it, when they 

 are called exocardial murmurs. But other murmurs are due to changes in the quality or 

 amount of the blood, when they are spoken of as uremic murmurs. In the study of all murmurs, 

 note their rhythm or exact relation to the normal sounds, their point of maximum intensity, and 

 the direction in which the murmur is propagated. ] It is rare that tumours or other deposits 

 projecting into the ventricles cause murmurs, unless there be present at the same time lesions 

 of the valves and disturbances of the circulation. The cardiac murmurs are always related to 

 the systole or diastole, and usually the systolic are more accentuated and louder. Sometimes 

 they are so loud that the thorax trembles under their irregular oscillations {fremitus, fremisse- 

 ment cataire). 



In cases where diastolic murmurs are heard, there are always anatomical changes in the cardiac 

 mechanism. These are insufficiency of the arterial valves, or stenosis of the auriculo- ventricular 

 orifice (usually the left). Systolic murmurs do not always necessitate a disturbance in the 

 cardiac mechanism. They may occur on the left side, owing to insufficiency of the mitral 

 valve, stenosis of the aorta, and in the calcification and dilatation of the ascending part of the 

 aorta. These murmurs occur very much less frequently on the right side, and are due to 

 insufficiency of the tricuspid and stenosis of the pulmonary orifice. 



Functional Murmurs. Systolic murmurs often occur without any valvular lesion, although 

 they are always less loud, and are caused by abnormal vibrations of the valves or arterial walls. 

 They occur most frequently at the orifice of the pulmonary artery [and are generally heard at 

 the base], less frequently at the mitral, and still less frequently at the aortic or the tricuspid 

 orifice. Anaemia, general malnutrition, acute febrile affections, are the causes of these murmurs. 

 [Some of these are due to an altered condition of the blood, and are called hremic, and others 

 to defective cardiac muscular nutrition, and are called dynamic ( WalsJie).] 



Sounds may also occur during a certain stage of inflammation of the pericardium (pericarditis) 

 from the roughened surfaces of this membrane rubbing upon each other. Audible friction 

 sounds are thus produced, and the vibration may even be perceptible to touch. [These are 

 " friction sounds, and quite distinct from sounds produced within the heart itself.] 



55. DURATION OF THE MOVEMENTS OF THE HEAET. The heart con- 

 tinues to beat for some time after it is 

 cut out of the body. The movement 

 lasts longer in cold-blooded animals (frog, 

 turtle) extending even to days than in 

 mammals. A rabbit's heart beats from 

 3 minutes up to 36 minutes after it is cut 

 out of the body. The average of many 

 experiments is about 1 1 minutes. [Waller 

 and Reid recorded the ventricular contrac- 

 tions of a rabbit's heart 72 minutes after 

 its excision. Fig. 52 shows the prolonga- 

 Fig. 52. tion of the ventricular systole in an ex- 



Curves of excised rabbit's heart, 1, 6 mins. after cised rabbit's heart, the movements being 

 excision; 2, 10 mins.; 3, 20 mins.; 4, 70 recorded by a lever resting on the heart] 

 mins. (after frailer a>id Reid). p anum found tbe kst tface of contract i on 



to occur in the right auricle (rabbit) 15 hours after death ; in a mouse's" heart, 46 

 hours 5 in a dog's, 96 hours. An excised frog's heart beats, at the longest, 2 J days 



