136 FOURTH REPORT— 1834. 



was opened : whilst the animal lay on its back, the heart was vi- 

 sibly elevated during the contraction of the ventricles, and even 

 the apex tvu-ned upwards. When the hand was laid upon the 

 heart, the perceptible quivering was so powerful and so momen- 

 taneous, that it appeared impossible to assign the beat against 

 the ribs to any other cause than the systole of the ventricles, for 

 no agitation could be felt during the diastole. 



This conclusion agrees with that which Mr. Carlisle derived 

 from his experiments. The dissections also of this gentleman 

 account for the tilting of the apex of the heart. The muscular 

 fibres, which pass from the basis to the apex, are found by him 

 to be considerably longer on the front than on the back part. 

 They contract therefore more : the apex is drawn towards the 

 basis, but at the same time forward*. 



The causes of the two sounds which are perceptible by aus- 

 cultation, and which occur between two consecutive beats of 

 the heart, are scarcely yet determined to the satisfaction of phy- 

 siologists. The dull and more enduring sound is quickly followed 

 by one which is clearer and more brief, as was first well defined 

 by Laennec. They follow each other v,ith a slight interval, and 

 then there is a pause. Laennec attributed the first to the con- 

 traction of the ventricles, the other to that of the auricles ; but 

 the interval between the somids does not correspond to the in- 

 terval between these contractions. All appear to be agreed that 

 the first sound is synchronous with the pulse at the heart, and 

 therefore they assign the cause of this as the cause also of the 

 first sound. Thus, Corrigan and others deduce the first sound 

 from the contraction of the auricles, the second from that of the 

 ventricles ; Williams, the first from the contraction of the ven- 

 tricles, the second from the action of the valves; Hope, the first 

 from the contraction of the ventricles, the second from the ex- 

 pansion of the ventricles by the bloodf. 



Majendie, in a memoir read before the Academy of Sciences 

 of Paris, February 1834, has lately objected to all these explana- 

 tions. He could perceive no sounds when the heart was laid 

 bare; and therefore concludes that they cannot proceed from the 

 respective play of its different cavities, nor from the action of the 

 heart upon the blood, nor of the blood upon the heart. He then 

 institutes a set of experiments, in order to discover the true 

 cause of the phsenomena in question. He found that though all 

 sound ceased when the sternum was removed, yet ^vhen elastic 

 bodies were brought in contact with the heart, sounds, variable 

 according to the nature of those bodies, were produced : when 



* Vide Reports of the British Association, vol. ii. p. 456. 

 f Compare Carlisle, loc. cit., ]). 458. 



