"In 1816, I was consulted by a young woman labouring under general symptoms of diseased heart, and in whose case percussion and the application of the hand were of little avail on the account of the great degree of fatness. The other method just mentioned [placing the ear to the chest] being rendered inadmissable by the age and sex of the patient, I happened to recollect a simple and well-known fact in acoustics, and fancied it might be turned to some use on the present occasion. The fact I dllude to is the great distinctness with which we hear the scratch of a pin at one end of a piece of wood, on applying the ear to the other. Immediately, on this suggestion, I rolled a quire of paper (24 sheets) into a kind of cylinder and applied one end of it to the region of the heart and the other to my ear, and was not a little suprised and pleased, to find that I could thereby percieve the action of the heart in a manner much more clear and distinct than I had ever been able to do by the immediate application of teh ear. From this moment I imagined that the circumstance might furnish means for enabling us to ascertain the character, bot only of the action of the heart, but of every species of sound produced by the motion of all the thoracic viscera, and, consequently, for the exploration of the respiration, the voice, the ronchus, and perhaps even the fluctuation of fluid extravasated in the pleura or the pericardium. With this conviction, I forthwith commenced at the Hospital necker a series of observations from which I have been able to deduce a set of new signs of diseases of the chest, for the most part certain, simple, and prominent, and calculated, perhaps, to render the diagnosis of the diseases of the lungs, heart, and pleura, as decided and circumstantial, as the indications furnished to the surgeon by the introduction of the finger or sound, in the complaints wherein these are used."

"The first instrument which I used was a cylinder of paper, formed of three quires, compactly rolled together, and kept in shape by paste. The longitudinal aperture which is always left in the centre of the paper thus rolled, led accidentally in my hands to an important discovery. This apperture is essential to the exploration of the voice. A cylinder without any aperture is best for the exploration of the heart: the same kind of instrument will indeed suffice for the respiration and ronchus; but both these are more distinctly perceived by means of a cylinder which is perforated throughout, and excavated into somewhat of a funnel shape, at one of its extremities, to the depth of an inch and a half. The most dense bodies do not, as might have been expected from analogy, furnish the best materials for these instruments. Glass and metals, exclusively of their weight and the sensation of cold occasioned by their application in winter, convey the sounds less distinctively than bodies of inferior density. Upon making this observation, which at once surprised me , I wished to give a trial to materials of the least possible density, and, accordingly, caused to be constructed a cylinder of gold-beater's skin, inflated with air, and having the central aperture formed of pasteboard. This instrument I found to be inferior to all the others, as well from its communicating the sounds of the thoracic organs more imperfectly, as from its giving rise to foreign soundsm from contact of the hand, &c."

"Bodies of moderate density, such as paperm the lighter kinds of wood, or Indian cane, are those which I found preferable to others. This result is pehaps in opposition to an axiom in physics; it has, nevertheless appeared to me one which is invariable. In consequence of these various experiments I now employ a cylinder of wood, and inch and a half in diameter, and a foot long, perforated longitudinally by a bore three lines wide, and hollowed out into a funnel shape, to the depth of an inch and a half at one of its extremities. It is divided into two portions, partly for the convenience of carriage, and partly to permit its being used of half the usual length. The instrument in this form--that is, with the funnel-shaped extremity,--is used in exploring the respiration and ronchus: when applied to the exploration of the heart and the voice, it is converted into a simple tube, with thick sides, by inserting into its excavated extremity a stopper or plug traversed by a small aperture, and accurately adjusted to the excavation. This instrument I have denominated the Stethoscope. The dimensions mentioned are not a matter of indifference. A greater diameter renders its exact application to certain parts of the chest, impracticable ; greater length renders its retention in exact appostion more difficult, and when shorter, it is not so easy to apply it to the axilla, while it exposed the physician too closely to the patient's breath, and, besides, frequently obliges his to assume an inconvenient posture,--a thing above all others to be avoided, if we wish to observe accurately. The only case in which a shorter instrument is useful is where the patient is seated in bed or on a chair, the head or back of which is close to him : then it may be more convenient to employ the half-length instrument."