REPORT ON ANIMAL PHYSIOLOGY. 137 



the sternum of a Goose was raised and replaced, the sound was 

 annihilated and reproduced at pleasure ; when air or water was 

 injected into the left pleura, so as to keep the heart at a distance 

 fi-om the thorax, no sound could be perceived. Further, he found 

 that if he introduced a slip of metal, thin and flat, into the thorax 

 of a Dog, so as to prevent the shock of the apex of the heart 

 against the parietes of the thorax, though the heart acted vio- 

 lently, the dull sound ceased ; if introduced so as to prevent the 

 right ventricle touching the thorax, the clear sound ceased. 

 Majendie hence deduces the first sound from resonance of the 

 thorax, caused by the stroke of the apex ; and the second from 

 resonance of the thorax, caused by the impulse afforded by the 

 heart, under sudden dilatation from the influx of blood, to the 

 anterior parietes of the right side of the chest. 



Bouilland, in a letter to the Academy of Sciences, has pro- 

 tested against Majendie's explanation ; asserting that it does 

 not satisfy the conditions, and raises a doubt concerning the va- 

 lidity of that theory alone which assigns the double soimd to the 

 play of the valves; (Romanet, in a recent inaugiu-al dissertation, 

 having maintained that the one sound arises from the shock given 

 by the blood to the tricuspid and mitral valves, the other to the 

 shock on the sigmoid valves of the aorta and pulmonary artery ; 

 and E. L. Bryan the same in the Lancet.) Bouilland further 

 alleges his own experiments. No sounds were heard when the 

 heart pulsated being emptied of its blood; they were heard when 

 the heart in situ was laid bare, and had no connexion with the 

 walls of the thorax. He further objects, that Majendie's theory 

 does not account for the varieties of sound produced by organic 

 lesions of the valves ; nor for the fact, that sounds may be heard, 

 as though distant, when fluid fills the pericardium and prevents 

 the heart from reaching the thorax. 



Here this subject rests for the present; but Majendie has un- 

 dertaken to examine, in a second part of his memoir, whether his 

 explanation will account for all the particular circumstances con- 

 nected with each of the sounds of the heart. 



Cause of the Heart's Action. — Haller, from observing that the 

 heart continues to beat for a considerable time even when re- 

 moved from the body ; and that its contractions, in the body, 

 may be affected by the direct application of mechanical and che- 

 mical stimuli to its fibres, whilst he coiild not influence them by 

 imtation of the cardiac nerves, concluded that its power of con- 

 traction is inherent, and totally independent of the nervous sy- 

 stem. His theory was afterwards fortified by the dissections of 

 Scemmerring and Behrends, which appeared to show that the 

 cardiac nerves are distributed to the vessels of the heart alone. 



