208 



heard through the other cup. Thus while the two sounds, being 

 of like character, and one being more intense than the other, can 

 be heard only in one ear at the same time, an admirable opportu- 

 nity is obtained for contrasting the extent, and some of the qualities, 

 of the sounds of the two parts, by placing the cups alternately and 

 rapidly upon the two spots respectively. Vocal extussive resonance 

 in two parts of the thorax, is well contrasted with the two tubes 

 employed at once, or in immediate succession. 



The sounds of the two sides of the heart, and of the valves of the 

 two great arteries proceeding from that organ, are, by means of the 

 stethophone, very advantageously dealt with. By placing it over 

 the two sides of the heart, or the origin of the two arteries^we ascer- 

 tain the character and loudness of the sounds of these parts. One 

 cup being placed over the aorta, and the other over the pulmonary 

 artery, if the sounds they collect differ in character, one sound is 

 heard in one ear, and another in the other ear. We may have at the 

 same moment an aortic murmur and a healthy pulmonary artery 

 sound, one sound in one ear, and another sound in the other ear. But 

 when it is desired to listen to each sound singly and in succession, 

 the instrument will still be available, for the cups may be applied 

 singly and in succession, thus affording ample means for contrast. 



In cases of disordered heart, in which it is desired to discover 

 whether the sounds of the two sides of the heart are synchronous, the 

 stethophone affords the most satisfactory mode of investigating the 

 fact. With it, we virtually place our two ears over the two sides of the 

 heart ; and if one side sounds at all after the other, the fact is made 

 known, and the end of one sound and the beginning of another are 

 clearly and distinctly defined. With the ordinary stethoscope this is 

 impossible ; for where one sound is heard, the other may be inaudible, 

 and long before the head or stethoscope can possibly be adjusted at 

 another part, the second sound has taken place, and is long since over. 



In conclusion, I may perhaps be permitted to say, that the dif- 

 ferential stethophone proves a great auxiliary in examining the heart 

 with the cardioscope or sphygmoscope, which I had the honour to 

 exhibit to this Society two years ago. While the latter instrument 

 exhibits the movements of the heart, the stethophone informs us of 

 their sounds, in a more complete manner than can be otherwise 

 effected ; and from the stethophone permitting of auscultating two 



