"I have been promising myself for some time to write in protest against the frauds of instrument-makers in the manufacture of the stethoscope which bears my name. My instrument was not patented, as it should have been, for the purpose of needed regulationas to the quality of work and reasonableness of price. Therefore it is essential for an instrument-dealer to order a lot made by an irresponsible manufacturer, and sell them to unsuspecting medical men, as the real article, at an unreasonable proceed. This has been done in two instances in New York, and one in Chicago, to my knowledge. In consequence, my attention has been called to the most awkward and imperfect imitations, under the name "The Denison Stethoscope," and I have been chagrined to see joints uneven and loose, tubes impervious or partly occluded and especially the flexible portion made with inflexible rubber tubing, with no regard whatever to my directions.

In London, Down Brothers have made a pretty [good] instrument, excepting their poor adjustment of the spring, but in this country [the USA] George Tiemann & Co. are the only ones whose make I can recommend. They have come nearer than any other manufacturer that I know of in following the requirements of a perfect binaural stethoscope which desiderata I will state as follows:

1st. THE SMOOTH INNER CALIBRE, large size, and gradually decreasing from the bell to the ear-ending, in imitation of the speaking tubes used for deaf persons. The law of sound is like that of light transmission, i.e., the angles of incidence and reflection are equal; and that transmission is aided by the trumpet-shaped bell and gradually decreasing size of the smooth inner surface of the tubes.

2nd. THE CONTINUOUS TRANSMISSION OF SOUND-This must be natural, so hard rubber or celluloid are preferable to metal for the tubes, as the latter givesa high pitch and metallic sound tothe sounds heard. The joint betweent he bells and the main tube, and between thwe arms and the flexible tubes, are made by the even and perfect fitting of slightly conical tubesinto each other making the whole instrument as if of one piece, as far as the transmission of sound is concerned. Probably the larger part of the sound is transmitted through the stethoscopic substance than through the hollow cavity.

3rd. THE CONSTRUCTION OF THE FLEXIBLE TUBES- The coiled wire for these tubes, which lines the usual rubber tubes and is itself lined with smooth soft rubber, is made to impinge at each end of each tube against the gutta-percha, so that a nearly perfect transmission of sound is obtained. This is the part that Tiemann & Co. alone have succeeded in rightly making, and is is an important feature of my stethoscope.

4th. THE EAR ENDINGS as lately made are acorn shaped, with openings so turned as to be directed directly toward the drums of the ears. This is a compromise from what I wanted, which was to have the lower and forward side of these tips bulge as to fill the space behinf the tragus, and leave the hole above and back immediately in fronmt of the auditiory canal. The difficulty of fitting variously shaped ears with perfectly adapted ear-tips is considerable with any other than the even conical pattern, I thinkm ought to be overcome.

5th. THE SPRING ATTACHMENT to pull together the arms is adjustable so that all the pressure of the ear-tipe can be obtained that the listener can stand with comfort. This much pressure is desireable for perfect transmission of sound.

6th. THE ORDINARY BELL ENDINGS are as follows: The stationary bell, with slightly flaring rim one and one-eighth inch in diameter, which is large enough to use in examination of infants and in the detection of valvular lesions. The medium-sized bell, which has a rim one and one-half inch in diameter and sufficiently flaring to give a good impinging surface against the chest, is the size ordinarily used. The soft rubber bell, rather thin and flexible, is intended to crowd into the medium sized bell, giving a one-fourth projecting rim or soft rubber for use on uneven surfaces, as in much emaciated consumptives.

7th. THE LARGE BELL FOR STETHOSCOPIC PERCUSSION- This is not, as has been assumed, for use held against the chest-wall, but for gathering the waves of sound emitted fromt he open mouth during expiration while forcible percussion is being made over portions of the lung where softening, bronchiectasis, or excavation is suspected. The concussion of the air contained in the thorax carried with it the succession, the cavernous, or the cracked-metal sounds which accompany the three above-named conditions, and by holding this large bell two inches from the patient's mouth, and percussing during expiration, they are distinguished better than can be done in any other way. Indeed, in thin chested persons with superficial excavations connected with a main bronchus, the fingernail percussion will nicely and accurately outline the limits of the excavation. the cracked-pot or hollow sounds are altered in various ways, a slushy or succession quality being sometimes imparted to either, according to the amount of moisture or breaking down of lung tissue elevated this stethoscopic percussion to a first place in the are of physical diagnosis. It is certainly coequal with ordinary percussion, and second, if at all, only to ausclutation.

The test I suggest of a good stethoscope is not, as assumed by Dr. Valentine in his article in the MEDICAL RECORD of July 16th, to hold the medium sized bell against to face of a watch, but put the watch on a show -case or table, cover it with the palm of the hand, then press the bell against the back of the hand. The clearness with which the working of the machinery is heard is the criterion of perfection in the instrument. By this test seven-eighths of the other stethoscopes sold fall short of their proper utility. I am willing to have my instrument, if properly made, tried by this testand if anyone will improve on mine as much as I have improved on the ordinary kind, I will have his make if it costs $50. I do not believe, however, that there is room enough in the perfect reproduction of auscultation sounds for so much improvement, unless it would be a telephonic stethoscope, which would necessitate and electric battery accompaniment.

Portability and cheapness of construction are not cardinal points in a good stethoscope. Utility should be considered first, last, and chiefly. Yet the former points should not be lost sight of in making my instrument. It should be as short and compact as flexibility and convenience of use will allow, and should be proportioned in its different parts as shown in the accompanying cut."