Assuming that a difference on percussion is not clearly made out, super added sound may at once determine that local change of some sort has passed upon one lung ; but in its absence, or for further confirmation of its cause when present, we compare carefully by auscultation corresponding portions of either lung. It may happen that on one side the breathing is stopped by a plug of mucus in one of the tubes : this may be removed by causing the patient to cough and dislodge the obstruction. In doubtful cases the act of coughing is of use in other ways, by changing the character of superadded sounds, and also by causing the patient to take a deeper inspiration than we can get him to do by ordinary means.
Such a slight condition of emphysema as may possibly exist with no relative difference in percussion resonance, is of no practical value, except as it modi fies the snperadded sounds of bronchitis when any such are present ; our chief concern is to be able to detect with some degree of certainty the early deposit of tubercle. Rational diagnosis alike seeks to avoid forming hasty conclusions from insufficient premises, and neglecting evidences which, however slight, are of real import ; and with this view the indications of early deposit have been ranged in the last subdivision of this section pretty nearly in the order of their importance. It is to be remembered that alteration of rhythm, or quality of breath-sound, is much more important than mere londneas or distinctness, and that naturally both the breatlung and the voice are louder on the right side of the chest than the left.
A word must be said of other phenomena as evidence of consolidation, which are derived, not from the lungs themselves, but from the sounds pro duced in the heart and arteries, which are transmitted through the lung. When the heart-sounds are heard more loudly at the right apex than at the left, or a blowing arterial murmur is heard in the subclavian artery, generally on the left side, there is reason to suspect consolidation; but both are unques tionably only of value as confirmatory of other signs.
Such is a general outline of th% evidence as to the condition of the lungs derived from the combination. of percussion resonanee and alterations in the bre,ath and voice-sounds in the clavicular region. Many of the more obscure points require for their elu
cidation an examination of the other parts of the chest, and in all cases a diagnosis must never be attempted without making it; the superadded sounds have yet to be considered, and my object has been to place the changes already spoken of in such a simple point of view as to lead the student by logical analysis to form for himself a correct opinion of the state of the patient. For this reason many of the more delicate modifications which find place in elaborate works on auscultation and percussion have been purposely omitted; to a practised ear such varieties may all be sufficiently intelligible, as indicating peculiar conditions of the subjacent tissue ; to the student they are only productive of con fusion. Let us never for a moment forget, that these investiga tions, as aids to diagnosis, ought not to serve as an opportunity for a parade of skill on the part of the observer, but are to be instituted solely for the better determining the form of disease under which the patient labors. At the same time the student ought not to be deterred from making himself acquainted with all the more complex phenomena of auscultation; for in this, as in all other branches of knowledge, the man who is most familiar with the more abstruse facts will most readily appreciate the simpler ones; and the evils that have resulted from paying too great attention to physical diagnosis have arisen quite as much from imperfect knowledge of the facts it discloses, as from dis regard to symptoms derived from other sources. In the exercise of a sound judgment, and with the view simply of ascertaining the condition of disease, and its most appropriate treatment, a practised ear will be of essential service ; in following the paltry object of a display of skill in determining the exact condition of an obscure case, the most dextrous is constantly misled ; I would even add that the self-satisfying curiosity which seeks to investi gate all the morbid phenomena with reference only to post-mor tem appearances is a less estimable than that which, while satisfied with a more limited knowledge, has its sole aim in alle viating suffering and curing disease.