HEART. 



617 



adds the sudden separation of the semilunar 

 valves when the blood is forced into the large 

 arteries; by Mr. Carlisle to the rushing of the 

 blood along the inner surface of the large 

 arteries during the systole of the ventricles.* 

 Dr. Hope, in the appendix to the second 

 edition of his work, describes it as consisting, 

 1st, possibly of a degree of valvular sound; 

 2d, of a loud smart sound produced by the 

 abstract act of a sudden jerking extension of 

 the muscular walls, in the same manner that 

 such a sound is produced by similar extension 

 of the leather of a pair of bellows; to avoid 

 circumlocution, he calls it the sound of exten- 

 sion ; 3d, a prolongation and possibly an aug- 

 mentation of this sound by the sonorous vibra- 

 tions peculiar to muscular fibre." Dr. C. J. B. 

 Williams has very justly objected to the correct- 

 ness of the second cause here adduced as 

 aiding in the production of the first sound, as 

 the phrase " sound of extension" is obviously 

 contradictory when applied to a contracting 

 muscle.f Dr. C. J. B. Williams maintains 

 " that the first sound is produced by the mus- 

 cular contraction itself," the clearness of which 

 is increased by the quantity of blood in the 

 heart " affording an object around which the 

 fibres effectually tighten, whilst the auricular 

 valve, by preventing the reflux of the blood, 

 increases its resistance, and thus adds to the 

 tension necessary for its expulsion." He was 

 first led to the adoption of this opinion by the 

 observations of Enman and Wollaston upon 

 the existence of a sound accompanying every 

 rapid muscular contraction. This opinion he 

 afterwards put to the test of experiment, the 

 results of which we give in his own words. 

 " Experiment 1st, observation 8th; I pushed 

 my finger through the mitral orifice into the 

 left ventricle and pressed on the right so as to 

 prevent the influx of blood into either ventricle ; 

 the ventricles continued to contract strongly 

 (especially when irritated by the nail of the 

 finger on the left), and the first sound was still 

 distinct, but not so clear as when the ventricles 

 contracted on their blood. Observation 9th. 

 The same phenomena were observed when both 

 the arteries were severed from the heart." He 

 also found in other observations that the first 

 sound was louder over the surface of the ven- 

 tricles than over the origin of the large arteries, 

 which is in direct opposition to the opinion of 

 those who believe that this is produced by the 

 rush of blood along the great arteries. That 

 the first sound is not dependent upon the closing 

 of the auriculo-ventricular valves, he also 

 ascertained from observations, in which the 

 closure of these valves was partially or com- 

 pletely prevented, and yet the first sound was 

 still heard. Besides, this sound continues 

 during the whole of the ventricular systole, 

 while the shutting of the valves must take place 

 and be completed at the commencement of the 

 systole." That the collision of the particles of 



* As Mr. Carlisle is a member of the Dublin 

 Heart Committee, we must now consider him as 

 concurring with the report of that Coiuuiittce. 



t Medical Gazette, Sept. 1835. 



fluid in the ventricles coes not produce this 

 sound he was convinced from observations, in 

 which it continued although there was no blood 

 in the ventricles. 



Though we must admit that these experi- 

 ments of Dr Williams prove that part at least 

 of the first sound is caused by the muscular 

 contraction of the ventricles, yet we must con- 

 sider it still problematical, until we obtain 

 further observations, whether it produces the 

 whole of that sound, for it is very possible that 

 some of the other circumstances attending the 

 systole of the heart may increase its intensity. 

 M. Marc d'Espine has maintained that both 

 sounds depend on muscular movements; the 

 first sound upon the systole, and the second 

 upon the diastole of the" ventricles. The Dub- 

 lin Committee have in the meantime concluded 

 that the first sound is produced either by the 

 rapid passage of the blood over the irregular 

 internal surface of the ventricles on its way 

 towards the mouths of the arteries, or by the 

 bruit musculaire of the ventricles, or probably 

 by both these causes. We must wait for further 

 experiments before this question can be fairly 

 settled.* 



Second sound. Later experimenters appear 

 to be more nearly agreed about the cause of 

 the second sound than that of the first sound. 

 M. Rouanet appears to have been the first who 

 publicly maintained the opinion that the second 

 sound was dependent upon the shock ot blood 

 against the semilunar valves at the origin of 

 the aorta and pulmonary artery. M. Rouanet 

 himself acknowledges that he owed the sug- 

 gestion to Dr. Carswell, at that time studying 

 in Paris, who came to that conclusion by a 

 beautiful process of reasoning upon the pheno- 

 mena which presented themselves in a case of 

 aneurism of the aorta. The same opinion has 

 been supported by Billing, Bryan, Carlisle, and 

 Bouillaud.f It is, however, to Dr. C. J. B. 



* The London Committee, in their report given 

 in at the meeting of the British Scientific Associa- 

 tion for 1836, have adduced some additional expe- 

 riments in favour of the opinion that the first 

 sound of the heart depends upon muscular con- 

 traction. It appeared to them that the sound pro- 

 duced by the contraction of the abdominal muscles 

 as heard through a flexible tube resembles the 

 systolic sound. They, however, admit that though 

 " the impulse is not the principal cause of the first 

 sound, it is an auxiliary and occasional cause, 

 nearly null in quietude and in the supine posture, 

 but increasing very considerably the sound of the 

 systole in opposite circumstances. " From the great 

 care with which these experiments appear to have 

 been performed, we believe that we are now fully 

 justified in adopting this explanation of the cause 

 of the first sound. The Dublin Committee, in their 

 report given in at the same time, also detail some 

 experiments which they believe to be confirmatory 

 of their former conclusions. See Sixth Report of 

 British Scientific Association. 



t In justice to Dr. Elliott, of Carlisle, I must 

 state that I find, on consulting his Thesis De 

 Corde Humano, published in Edinburgh in 1831, 

 that he states (p. 53) that he believes that the 

 second sound of the heart is dependent upon the 

 rush of blood from the auricles into the ventricles 

 during their diastole, and also upon the sudden 

 napping inward of the sigmoid valves at the origin 

 of the large arteries by the refluent blood. 



