D. M. Cammann

“ Sound, in passing to the ear, is conveyed through two hollow chambers--one in the chest-piece, and the rubber bulb--both of which act as resonators and increase its intensity. Not only is the intensity of the sounds increased, but their true quality is better appreciated. ”

“ Snelling, is of advantage in applying it more closely to the inequalities of the chest. In most of the instruments now made, the rubber band which serves to draw the two tubes together is replaced by a spring. In the latest improvement the spring is placed in the screw which binds the tubes together. Great care is required in the construction of the stethoscope, and many defective ones are sold. The knobs on the ear-pieces must neither be too large nor too small; if too small, they cause pain by their pressure; if to large, they allow external sounds to enter the ear. ”

“ Another advantage is that the two hands of the auscultator are left free to practice the method of auscultatory percussion--a method which has not yet received the attention it deserves, and which, it is to be hoped, will come into more general use. ”