In a late visit to Paris, I availed myself of the opportunity of attending the principal hospitals; of inquiring into the general practice of French medicine; and of studying, at the hospital of La Charité, the method brought to so much perfection by M. Laennec, of investigating the diseases of the chest; in regard to which, I had also the advantage of receiving every kind attention and personal instruction from this distinguished physician. The method of which I now purpose to offer a brief account, embraces the use of percussion and of the stethoscope. It appears that percussion was first practised by Avenbrugger in Germany, who published a treatise on the subject in the year 1761, which was translated into French by the celebrated Corvisart, with commentaries, in 1808. This author, in his Treatise on the Diseases of the Heart, constantly founds much of his diagnosis on the indications afforded by percussion. The method consists in striking the respective parts of the chest, which return a hollow kind of sound, when the contents of this cavity are in a healthy state; but give a duller sound, when, from any cause, there is impediment to the free entrance of air into the cells of the lungs. When the obstruction is considerable, the perception is very much the same as when you strike upon the thigh. The sound is flat instead of hollow. Simple as it may appear, there is a considerable tact in the mode of percussing; and it is of importance to practise it in aid of the information derived from the stethoscope. The linen covering over the chest may remain, but thick dress should be removed, and the surface also ought to be smooth. The integuments should be rendered rather tense by the favourable position of the arms. The four fingers being held close, bent, and a little curved, the chest is to be struck rather sharply and in quick succession; and when the indication of obstruction is manifest by the dulness of sound, the corresponding part on the opposite side, is to be struck with equal force; nice care being observed that all circumstances are equal; as for example, the kind and strength of percussion, the quantity of covering on the part, and the position of the patient. At small points of examination, it will sometimes be convenient to use, in the same manner, only two fingers; or, now and then, on a broad surface, the flat hand, percussing rather slowly and gently. M. Laennec displays no less skill and accuracy in his mode of percussion than in the use of his stethoscope; and he attaches great importance to it as an auxiliary source of information.