336 Sir R. Quaiii. On the Mechanism by which 



were obtained, and, as in niy preceding experiments, the heart was 

 exposed, and the circulation kept up by artificial respiration. A 

 stethoscope being applied to the organ, sounds were distinctly heard. 

 The superior and inferior venae cava? were now compressed with a 

 bull-dog forceps, and the pulmonary veins by the finger and thumb ; 

 the heart continuing its action, a stethoscope was again applied, and 

 neither first nor second sound was heard. After a short space of 

 time, the veins were allowed to pour their contents into both sides of 

 the heart, and both sounds were instantly reproduced. On the veins 

 being again pressed, all sound was extinguished, notwithstanding 

 that the heart contracted vigorously. Blood was again let in, and 

 both sounds restored. I have thus frequently interrogated the 

 same heart for upwards of an hour, and always with the like result" 

 (p. 25). 



These experiments of Professor Halford must be accepted as suffi- 

 cient to refute the view of the German observers just quoted. 

 Another source of fallacy in making experiments of this kind is that 

 a very slight stroke of the muscle or ventricle against the end of the 

 stethoscope is sufficient to produce a very loud and distinct sound, 

 resembling the first sound. If the palm of the hand, for instance, be 

 pressed gently over the ear, and the back of the hand be touched by 

 a finger of the opposite hand, it will be felt how slight a stroke is 

 sufficient to produce a very distinct sound. Observers (Ludwig and 

 Dogiel) have recognised the difficulty of isolating muscle from the 

 instrument conveying the sound, and they have placed, the empty heart, 

 still contracting, in a jar containing defibrinised blood or warm water, 

 from the side of which a neck is projected, covered by a thin layer 

 of india-rubber. At each contraction of the heart a distinct 

 sound, resembling the first sound of the heart, was heard. But 

 the flapping of the heart against the water was quite sufficient to 

 produce the sound which was conveyed to the ear ; aod I cannot see 

 in such an experiment sufficient evidence of the sound of muscular 

 •contraction being the cause of the first sound of the heart. 



Experiments of another kind have been employed to show that the 

 oontraction of the muscle is a source of the sound. Hurt hie* and 

 Einthovenf show graphically that the first sound begins with the 

 very beginning of the systole, before the ventricle has got power 

 "to open the valves." This observation is entirely consistent with 

 the view I am about to propose. The moment the ventricle begins to 

 contract, the impact of the blood against the semi- lunar valves com- 

 mences, producing the commencement of the sound, not when the 

 valves are thrown open, The valves being connected with the fibroid 



* ' Pfluger's Arcliiv,' vol. 60, p. 263. 

 + Ibid., vol. 57, p. 617. 



