HEART. 



615 



seems to have been almost implicitly adopted un- 

 til the appearance of a paper by the late Professor 

 Turner, in 1829. Professor Turner there re- 

 called to the attention of medical men the 

 observations of Harvey, Lancisi, Senac, and 

 Haller, upon the order of succession in which 

 the cavities of the heart contract, which appear 

 to have been forgotten amidst admiration at 

 the brilliancy of Laennec's progress. He also 

 pointed out from their experiments that if the 

 second sound was dependent upon the con- 

 traction of the auricles, it ought to precede 

 instead of following the first sound, and that 

 the pause ought to occur after the first sound, 

 and not after the second. He also adduced, in 

 farther proof of Laennec's error, observations 

 drawn from the effects of disease, when, from 

 some impediment to the passage of the blood 

 from the right auricle into the ventricle, a dis- 

 tinct regurgitation takes place into the large 

 veins at the root of the neck, and showed that 

 in these cases the regurgitation marking the 

 contraction of the auricles occurs without any 

 accompanying sound ; that immediately after- 

 wards the impulse is felt attended by the first 

 sound, and that the second sound takes 

 place during the diastole of the ventricles 

 and the passive condition of the auricles. 

 He suggested that the second sound might be 

 accounted for by the falling back of the heart 

 into the pericardium during its diastole, to 

 which " the elasticity of the ventricles at the 

 commencement of the diastole, attracting the 

 fluid by suction from their corresponding auri- 

 cles, may perhaps contribute." Soon after the 

 appearance of Mr. Turner's paper, Laennec's 

 explanation of the cause of the second sound 

 appears to have been pretty generally aban- 

 doned ; and numerous attempts, both in this 

 country and in France, have since that time 

 been made to solve this difficulty. Some of 

 these explanations appear to be mere guesses, 

 occasionally at total variance with the anato- 

 mical structure of the organ, and at times pre- 

 senting even as wide a departure from its nor- 

 mal action as that given by Laennec himself. 

 Others, again, have entered upon an experi- 

 mental investigation of the subject with en- 

 lightened views of its anatomy and physiology, 

 have furnished us with much additional infor- 

 mation, and lead us to indulge in the pleasing 

 prospect that in a short time the matter will be 

 completely set at rest. 



The result of the experiments of Hope and 

 Williams, attested as they have been by various 

 gentlemen well qualified to judge of their 

 accuracy, also those of Mr.Carlisle, Magendie, 

 Bouillaud, and the Dublin Committee, have 

 satisfactorily determined that the account of the 

 order of the contractions of the heart, and 

 their isochronism to the sounds as stated by 

 Mr. Turner, are perfectly correct. As, how- 

 ever, so many different circumstances attend 

 each movement of the heart, any one of which 

 may be capable of producing these sounds, it 

 became a much more difficult matter, and one 

 requiring great perseverance and accuracy of 

 investigation, to determine upon what particular 

 one or more of these, each sound depends. 



For accompanying, and synchronous with the 

 first sound, we have the contraction of the ven- 

 tricles, the collision of the different currents of 

 blood contained there thus set in motion, the 

 approximating of the auriculo-ventricular valves, 

 the impulse of the heart against the chest, and 

 the propulsion of the blood along the large 

 arteries; while attending the second sound, we 

 have the diastole of the ventricles, and the rush 

 of a certain quantity of blood from the auricles 

 into the ventricles, the sudden separation of 

 the auriculo-ventricular valves towards the 

 walls of the ventricles, and the regurgitation of 

 part of the blood in the arteries upon the semi- 

 lunar valves, throwing them inwards towards 

 the axes of the vessels ; so we will find that 

 each of these in its turn has been thought ca- 

 pable of producing the sound which it accompa- 

 nies, and stillhas,oruntil lately had, its advocates 

 and supporters. As the subject is one surrounded 

 with numerous and unusual difficulties, and is of 

 comparatively recent investigation, it has fol- 

 lowed, as was to be anticipated, that as new 

 facts and observations are collected, many of 

 the opinions first promulgated on this question 

 have required to be modified or changed ; and 

 the scientific candour displayed by several of 

 these authors in renouncing former published 

 opinions is deserving of the highest praise. 



Several of the explanations of the cause of 

 the sounds of the heart proceed, however, upon 

 the supposition that the relation of these sounds 

 to the movements of the organ is different 

 from what has been here represented. We 

 shall merely state these without alluding to the 

 arguments adduced in support of them, as we 

 believe that they are founded upon inaccurate 

 observation. Sir D. Barry believed that the 

 first sound was synchronous with the diastole 

 of the auricles, and the second sound with the 

 diastole of the ventricles. Mr. Pigeaux, Dr. 

 Corrigan also until lately, Dr. Stokes, Mr. 

 Hart, and Mr. Beau, have maintained that the 

 first sound is synchronous with the diastole, 

 and not with the systole of the ventricles. Ac- 

 cording to Mr. Pigeaux, when the auricles 

 contract they project the blood against the walls 

 of the ventricle, and a dull sound (first sound) 

 is produced ; on the other hand, whilst the 

 ventricles contract, they project the blood 

 against the thin walls of the great vessels which 

 spring from them, and a clear sound (second 

 sound) is the result. Dr. Corrigan supposed 

 that the first sound was produced by the rush 

 of blood from the auricles into the dilating 

 ventricles, and that the second sound owed its 

 origin to the striking together of the internal 

 surfaces of the ventricles during their contrac- 

 tion, after they had expelled all their blood. 

 Mr. Beau believes with M. Magendie that the 

 first sound arises from the impulse of the 

 heart against the inner surface of the chest, but 

 differs from him in maintaining that this occurs 

 during its diastole, and not during its systole. 

 The second sound he believes to depend upon 

 the dilatation of the auricles. M. Piorry has 

 revived the obsolete and perfectly untenable 

 opinion of Nicholl, that the two ventricles 

 contract at different times, and attributes 



