There is one source of fallacy which must be avoided. When emphysema exists to a considerable extent throughout the chest, and has been accom panied by repeated attacks of bronchitis, it frequently happens that all the tubes are to a certain extent rigid and dilated. Now, if the emphysema be chiefly of the lower lobes, and one of the upper lobes be less affected than the other, the breathing may be almost entirely suspended throughout the chest. while the dilated bronchi of the least diseased structure give rise to sounds under one clavicle which have the character of being produced in larger spaces, and not in the vesicles; and on this side there is by comparison dulness on percussion. How do we know that this is not a case of consolida tion? Simply by considering the condition of the rest of the lung: we may be tolerably certain that, in extensive emphysema, the existence of tubercular or other consolidation is not to be looked for.
The cases comprised under 1 4 demand a little more consideration, because the information from percussion is unsatisfactory ; and the last series represents a most important class of cases—early phthisis, in which no infor mation can be obtained from the rest of the chest; superadded sounds, too, are often wanting ; and unless we can establish a distinct relation between general symptoms and auscultatory phenomena, our judgment must be held in suspense.
In health there is no great difference in the intensity of the breath and voice-sounds under each clavicle in the same individual; except that they are very slightly more intense on the right side than on the left. Scarcely any two individuals present sounds exactly alike, and what would be the effect of disease were it heard in one, is the normal condition in another. But though these limits of health have a very wide range, they have reference to a certain standard with which the student cannot too early make himself thoroughly familiar; and when in any particular case he finds the clavicular region on each side alike deviating from it, he must institute a comparison with the other parts of the chest.
A patient does not generally seek for relief from symptoms of emphysema alone ; it is a permanent condition of ill health which has been the growth of years, and has been increased by every cold i and it is only when bronchitis is superadded that he thinks of asking for medical advice. The sounds of bron chitis are then heard in addition, and hence it often happens with inexperi enced auscultators that the mingled sounds of the mixed diseases are taken as those of emphysema itself, and the possibility of emphysema without bron chitis is forgotten.
When partial dulness exists on both sides, from mere loss of resiliency of the ribs, the main source of error is the existence of a dilated bronchus. An elderly person who has long suffered from chronic bronchitis presents very often rather a Battened chest; the loss of elasticity in the ribs causes resist.
ance in percussion, and tends to give the stroke a dull sound ; the large tubes become thickened and dilated, with loss of elasticity; the vesicles do not expand and contract with their usual freedom, may be closed by thickened mucous membrane, or, when superadded sounds are present, by inspissated mucus : under such circumstances, just as happens in emphysema, blowing breath-sound both with inspiration and expiration may be present, with locally increased voice-sound; and inasmuch as the alteration in condition and espe cially in form of these tubes is unequal, the changes detected by auscultation are also unequal. When, in addition to this, the signs of general bronchitis are present. it becomes almost impossible to determine whether at the apex there may not be either tubercular consolidation or a number of small cavities, or whether there be only dilated bronchial tubes : and the final decision must rest more on correlative signs and symptoms than on those of percussion and auscultation ; and we shall have not unfrequeutly to wait till the general bron chitis be gone, before pronouncing a decided opinion. Should the case then be submitted to a fresh examination, and nothing remain but the ill-defined dulness on percussion, and a diffuse blowing-sound of expiration nearly equal on both sides, without the local distinctness of amphoric breath and voice sounds, we may conclude with great confidence that there never has been any tubercle.
It rarely happens that consolidation is equally advanced in both lungs, and as expert anscultator can generally detect a difference in shade between the dulness.of the two sides ; but I must confess that I have seen serious mistakes made in attempting to determine by percussion alone which of the two was the most solidified lung.
From the advanced stage in which the dulness on percussion ia unquestion able, it gradually passes, in cases of tubercular deposit, into that in which percussion fails in detecting consolidation at all : our means of appreciation are not sufficiently accurate, and the two sides of the chest are not even in health shaped exactly alike ; while the difficulty of course is increased when the deposit is deep-seated, and healthy, or nearly healthy structure interrenes between it and the parietes. But when auscultation is taken along with per cussion, the difference between the two sides becomes more apparent, and the existence of morbid structure is proved by the changes in rhythm and quality of breathing and loudness of voice, as well as by the superadded sounds, which not only differ from what is heard in the rest of the chest, but are also uneilual on its opposite sides. The expiration is always more audible and somewhat prolonged, while the inspiration is sometimes loud and harsh, sometimes weak and defective : the exaggerated voice-sound, in the latter instance, forming a most striking and trustworthy contrast.