616 



the dull sound to the contraction of the left 

 ventricle, and the clear sound to the contraction 

 of the right ventricle. Dr. David Williams, 

 while he believes that the first sound depends 

 upon the rush of blood into the large arteries 

 during the systole of the ventricles, attributes 

 the second sound to the musculi papillares, 

 which he considers as forming part of the val- 

 vular apparatus, causing the valves to strike 

 against the walls of the ventricles. These mus- 

 culi papillares do not, in his opinion, contract 

 during the systole of the ventricles, but imme- 

 diately afterwards, for the purpose of throwing 

 open the auriculo-ventricular valves. In a 

 former part of this article several circum- 

 stances are stated adverse to this opinion. 



We shall now proceed to the explanation of 

 the cause of these sounds given by those who 

 maintain the views of the rhythm of the heart 

 which we have here adopted, as resting upon 

 the concurrent testimony of numerous accurate 

 observers. These may be divided into those 

 who attribute both sounds to causes intrinsic to 

 the organ, or, in other words, to circumstances 

 occurring within the organ itself, and into those 

 who place them external to the organ, and 

 depending upon extraneous objects. The only 

 supporters of the latter opinion are Magendie 

 and his followers. Magendie maintains that 

 '* in contracting, and for causes long since known, 

 the ventricles throw the apex of the heart 

 against the left lateral part of the thorax, and 

 thus produce the first sound, z. e. f the dull 

 sound. In dilating, in a great measure under 

 the influence of the rapid influx of the blood, 

 the heart gives a shock to the anterior paries 

 on the right of the thorax, and thus produces 

 the second sound, the clear sound." In proof 

 of this, he states that on removing the sternum 

 of a swan (an animal selected expressly for 

 the experiment, as it interfered less with the 

 natural action of the heart than in the Mam- 

 malia), he found that the movements of the 

 heart produced no sound, while, on replacing 

 the sternum, and allowing the heart to impinge 

 upon its posterior surface as in the natural 

 state, both sounds were again distinctly heard. 

 He adduces several arguments drawn from the 

 action of the heart both in its healthy and dis- 

 eased state in favour of his opinion ; and he 

 ingeniously attempts to get rid of the objection 

 which must instantly suggest itself, that in 

 many cases, such as frequently occur in hyper- 

 trophy of the organ, the loudness of the sounds 

 is diminished, while the force of the impulse 

 is increased, by arguing that in these cases this 

 increased impulse depends rather upon a 

 heaving of the chest produced by the heart, 

 which from its increased size is brought close 

 to its inner surface, than upon a distinct im- 

 pingement upon it, such as takes place in the 

 healthy state. Dr. Hope, M. Bouillaud, Dr. C. 

 J. B. Williams, and the Dublin and London 

 Heart Commitees have, however, distinctly 

 heard both sounds of the heart, after that por- 

 tion of the chest against which it impinges had 

 been removed. It may, nevertheless, be objected 

 to these experiments, that as the stethoscope was 

 used in many of them, the impulse of the heart 



HEART. 



against the extremity may have produced an 

 effect similar to its impulse against the parietes 

 of the thorax. M. Bouillaud, having appa- 

 rently this objection in view, states that the 

 rubbing of the heart during its movements 

 against the extremity of the stethoscope, is 

 easily distinguished from the sounds of the 

 heart; and that he has distinctly heard both 

 sounds, though feebler than through a stetho- 

 scope, as was to be expected when nothing but 

 a cloth was interposed between his naked ear 

 and the surface of the heart. Dr. C. J. B. 

 Williams, in his experiments, heard both sounds 

 when the stethoscope was placed over the origin 

 of the large arteries, and where no external 

 impulse could take place ; and this observation 

 was repeated by the Dublin Committee. The 

 Dublin Committee heard both sounds through 

 the stethoscope, though feebler after the peri- 

 cardium had been injected with tepid water ; 

 and in another experiment they were also 

 heard when the ear was simply approximated 

 to the organ. From all these experiments, I 

 think there can be little doubt that the move- 

 ments of the heart, independent of all extra- 

 neous circumstances, are attended by a double 

 sound. As the impulse of the heart against 

 the chest must produce some sound, as any 

 one may convince himself by making the ex- 

 periment in the dead body, and as this occurs 

 during the systole of the heart, or, in other 

 words, during the first sound, it may increase 

 the intensity of that sound. Dr. R. Spittal,* 

 after relating several experiments in which a 

 sound similar to that of the first sound of the 

 heart was heard by tapping gently with the 

 apex of the heart or the point of the finger 

 against the chest, both when empty and when 

 filled with water, and after pointing out several 

 sources of fallacy which he supposes were not 

 sufficiently guarded against in the experiments 

 which we have adduced above as subversive of 

 this view, and which deserve the attention of 

 future experimenters, comes to the conclusion 

 that " it is highly probable that the percussion 

 of the heart against the thoracic parietes during 

 the contraction of the ventricles assists mate- 

 rally in the production of the first sound." 

 He is also inclined to believe " that the act of 

 the separation of the heart from the thorax after 

 its approach, which was found in his experiment 

 to produce a sharp, short sound, somewhat 

 resembling the ordinary sound, may in certain 

 circumstances be an assistant cause to the 

 second sound. "f Magendie's explanation of 

 the second sound is completely untenable. 



Among those who maintain that these sounds 

 depend upon causes intrinsic to the heart, the 

 Jirst sound is referred by Rouanet, Billing, 

 Bryan, and Bouillaud to the rapid approxima- 

 tion of the auriculo-ventricular valves during 

 the systole of the ventricles, to which Bouillaud 



* Edin. Med. and Surg. Journal, July 1836. 



f Though Dr. Spittal is inclined to believe that 

 the impulse of the heart against the chest has con- 

 siderable share in the production of the first sound, 

 he does not concur with Majc-ndie in the explana- 

 tion of the second sound. 



