STETHOSCOPT, 



191 



The binaural stethoscope (Fig. 3) of Dr. Camman, of New York 

 city, is unquestionably the best instrument known. Its name signifies 

 its peculiar advantages. Two tubes (one for each ear), suitably curved, 



Fig. 2. 



and each furnished with a rounded bulb for accurate fitting to the 

 opening of the ear, are connected at the other ends with a hollow cone 

 for application to the chest of the person examined. The cones or 

 chest -pieces are of various sizes, and are adjusted and used inter- 

 changeably according to the required extent of field which has its 

 limits between one and two inches in diameter. They are made from 

 ebonized wood, vulcanite, or soft rubber, the latter being required to 



Pia. 8. 



prevent painful pressure on uneven surfaces of the chest. In a part of 

 their course the tubes are elastic, the remainder being metallic. They 

 are so constructed as to be easily and perfectly adjustable to the ears 

 by softly elastic springs. By this arrangement both ears are not only 

 equally engaged with the same sounds, but other sounds are practically 

 excluded. This feature is fairly represented in the binocular micro- 

 scope and in the stereoscope, which possess the full advantages derived 

 from the use of both eyes. Thus the stethoscope heightens and places 

 in relief our auditory perception of the movements and conditions of 

 deep-seated vital organs, giving prominence to the lines and shades of 

 a picture otherwise flat and indistinct. It will, of course, conduct all 

 sounds communicated to it from without, thus making it necessary to 

 avoid all frictional contact with the instrument, even of the lightest 

 clothing ; and the listener will steady it deftly by thumb and finger to 

 escape confusion from a multiplicity of sounds. By the practiced ear, 

 however, most of the numerous adventitious sounds can readily be 

 eliminated and the attention successfully fixed on the one sought. 



The means next in importance in questioning the condition within 

 the thoracic cavity is percussion. It consists in striking upon the 

 chest with carefully-suited force with the tips of one or more of the 



