342 On the Production of the First Sound of the Heart. 



Fig. 1. — Diagram to illustrate Sir Richard Quain's theory of the mechanism 

 causing the first sound of the heart. 



A. Eeceptacle for water-supply connected by means of tubing B with bone 

 nozzle C tied into the left auricle. 



D. The left auricular appendix ligatured after escape of all air from the heart 



chambers. 



E. The left ventricle of the heart. 



F. The site of the right chambers of the heart which were removed after ligature 



of the coronary arteries KK. 

 H. Tubing connected with the aorta Gr and containing water representing the 

 aortic column of blood. 



If further the ventricle be compressed periodically in imitation of 

 systolic contraction, and allowed to relax in imitation of diastolic 

 relaxation, a sound closely resembling the first sound of the heart 

 will be produced when water is propelled from the ventricle into the 

 aorta, and another closely resembling the second sound when pro- 

 pulsive movement ceases, and the sigmoid valves again close under the 

 superincumbent weight of water in the aortic tubing. As the fluid 



