There is less chance of error when one lung is slightly emphyeematous its lower part, than when the same condition exists at the apex. If the sounds of bronchitis be limited to the resonant side, no mistake can be made, whether the difference on percussion be rightly or wrongly interpreted ; if they be heard on both sides, although more distinct on the duller one, the suspicion of con solidation there is not so apt to mislead as it is in the clavicular region : the possible varieties are detailed in the preceding pages chiefly in order that the student may be able to give to hiinself a consistent explanation of what he hears.
The cases of real difilculty are enumerated in 4, and though perhaps enough has been there stated to show the grounds upon which diagnosis is to be made, a recapitulation in a less • formal method may serve to make them more intelligible. We may at once exclude those in which some faint stetho scopic indication ekes out general symptoms, and shows that pleurisy or pneumonia is impending, or m actually present in minor degree, or is deep seated. Auscultation can do no more than lend a feeble iud, and no great reliance is to be placed upon it. We may also exclude those in which only imperfect information is derived from percussion, because the walls are too thick,and unequal (e. g., in the scapular region) to produce definite molts, while the other auscultatory phenomena are well marked and distinct, The cases to which we now refer are those in which the sounds of bronchitis are taken for something else, or those dependent on other causes are supposed to indicate ita presence.
The sounds produced by bronchitis include two very distinct classes—the sonorous and moist sounds : the former are not apt to cause mistakes ; and the only point to be remembered is, that when confined to one part of the chest, there is probably some cause for their localisation, which must be sought for in consolidation or dilatation, or inay be more vaguely trued out in a history of previous inflammation of the lung ; and thus, while explicitly pointing to bronchitis, they may be the means of detecting other and more permanent disease. Moist sounds, again, vary very much in character ; and the range of those which may be caused by bronclutis, and nothing more, is a very wide one : it is true in a general sense, that very fine sounds, even when not quite what may be called crepitation, are most probably excited by fibrin ous or tubercular deposit, and that very coarse or large bubbles are only heard when there is a cavity; but these limits cannot be strictly defined. One leading characteristic of the bronchial exudation is ita tendency to accumulate in the lower part of the chest, and therefore it is there that we seek for it ; and in a large proportion of cases moist sounds, heard there only, are clia tinctive of bronchitis. The exceptions are so few, that if heard equally on both sides, except there bp something inconmous m the history of the case --hiemoptysis, quick pulsg, &c.—it does not demand any very close investiga tion : it is only when they are confined to one side Oust we have to inquire whether there be not some consolidation or dilatation of the lung-tissue ex isting at the same time ; and when consolidation is found, the probabilities are very greatly in favor of past or present inflammation—very much against tubercle.
When the superadded sounds are not limited to the base, there may be found in the clavicular region or over the scapula sounds which closely re semble crepitation but we may at once dismiss the idea that the whole of them can be causea by pneumonia, unless the constitutional disturbanoe be very great indeed, and we are reduced to the hypothesis of disseminated tubercle or of bronchitis : we have the BS= hypoftsis to deal with, when the sounds at the apex are either coarser or sonorous. If the deposits of
tubercular matter be very wide apart. they may not produce any definite signs of consolidation—generally there is a difference between the two apices, but not invariably : the more nearly the sounds at the apex approach to crepita tion, the more distinct the evidence will be.
The cues are naturally divided by their history into the acute and chronic; those of recent date, with simply mucous expectoration or mixed mucilaginous looking sputa ; and those of long standing, in which the secretion is distinctly purulent or mucopus. In recent cases the mode of incursion very often in dicates the character of the disease, and is really much more trustworthy than the physical signs : in childhood the sounds may be clicking or squeaking. such as in adults we seldom meet with but in phthisis, and yet the case may be simply bronchitis ; it is at this age, too, that we most frequently find the equally disseminated tubercular deposit, which fails in giving evidence of con solidation. The true nature of such cases can only be determined by their history and general symptoms. Sonorous sounds at the apex are less likely than any other variety to have a tubercular source when moist sounds exist at the lower part of the chest : in adults, when tubercles are present, the sound, of whatever character, is generally as distinct in front as at the back of the chest, and very probably more so on one side than on the other.
In chronic cases the history is often so similar, whether there be tubercle or not, that less aid is derived from this source ; still, we may have a report of hsemoptysis, or suspicion may be aroused by the extreme rapidity of the pulse. the fine thin skin or clubbed nails of phthisis ; and so great is the im portance of such correlative symptoms, that the stethoscopist may be wrong, and the man who never practises auscultation, right, in the interpretation of tubercular disease of the lower lobes : all the physical signs are readily ex plained by the hypothesis of bronchitis, and the general symptoms are attri buted to the same cause. • Then, on the other hand, a more common error is to be guarded against that differences of sound at the apices necessarily indicate tubercles; rigidity and dilatation of tubes is so frequent in chronic bronchitis, producing a cer tain amount of blowing, breathing, and giving a degree of coarseness to the moist sounds in one part of the lungs, while a slight amount of emphysema, or the closure of some tube with mucus, causes a suppression of all sound in another, that it is not difficult to account, in a general way, for changes in bresth-sound and varieties of moist sound met with when there is no tubercle; but they are apt to mislead the inexperienced.
The difficulty of ascertaining the exact condition of the lower lobes, so far as the breath4ound is concerned, is very often increased by the closure of tubes just alluded to; and when the secretion is very abundant or much in spissated, no sound may reach the ear over a large portion of the posterior region, except a few large coarse bubbles.