the First Sound of the Heart is produced. 341 



distinctly heard over the base, and not at the apex." He remarks, 

 " We must not forget that one element of the sound, that produced 

 by the shock of the heart against the chest-wall, is absent.'** 



Another point of interest is that which has already been alluded 

 to in the case of typhus fever, as described by Dr. Stokes, namely, 

 that the sound disappears last over the semi-lunar valves, and also 

 that the returning sound is first heard in the same situation. 



It is also an object of great interest to compare the characters of 

 the two sounds in relation to the seat of their origin at the semi- 

 lunar valves. In the first sound we have the character of propulsive 

 force and sustained action, softer and more prolonged than the 

 second sound, which is sudden, sharp, and short, as if produced by 

 an abrupt mechanical disturbance. These distinctions, which may 

 be readily recognised in various degrees by careful observation, 

 serve to convince us that the sounds are both produced at the same 

 point : at the semi-lunar valves, each by its own single and simple 

 agency. 



D. Lastly, sounds resembling the first (and second) sound of the heart 

 can he produced artificially in accordance with the view contained 

 in the preceding communication. . . 



The experiment is thus made : a sheep's heart of good size (or 

 that of a calf) may be used. It must be carefully cleared from peri- 

 cardium, leaving the large vessels and pulmonary veins as far as 

 possible intact. The orifices of the pulmonary veins must be laid 

 into one, so as to permit a sufficient opening into the left auricle 

 through which to divide the attachments of the mitral cusps and the 

 musculi papillares in the left ventricle, taking care in doing this 

 not to injure the aortic segments when detaching the cusp that lies 

 next them. The coronary artery must next be ligatured, and also 

 the innominate artery where it springs from the aortic arch. The 

 right auricle and ventricle should be removed. Through the opening 

 made by laying into one the orifices of the pulmonary veins a bone 

 nozzle should be passed. It is well also to ligature the auricular 

 appendix and any points from which water may issue when the 

 ventricle is filled. To the posterior orifice of the nozzle rubber 

 tubing should be attached, communicating with a source of water 

 supply, placed on a higher level ; and another portion of rigid gutta- 

 percha tubing, about 3 feet long, should be introduced into the aorta 

 (see diagram, fig. 1). If now the ventricle be filled with water by 

 means of the tube in the left auricle, the water will of course pass 

 into the ventricle and thence up the aorta, a portion of the water 

 resting upon and closing the aortic sigmoid valves. 



* 6 Gazette Medicale,' p. 488 (1841). a ■ 



