D. A slight difference may exist, but the ear may fail to detect it. On comparison of corresponding portions of the two lungs, somewhere or other a difference in rhythm or quality of breath sound and in the intensity of the voice-sound is distinguished by auscultation ; and we will suppose that no corresponding changes are discovered in an examination of the rest of the chest. Fortu nately, there is very generally some superadded sound to guide our determination ; but when absent we have to decide what cir cumstances justify us in assuming the existence of disease in the upper lobes. The question is a weighty one, because here it is that tubercle is generally first deposited; but we must not forget that general symptoms indic,ating the possibility ought to be present to justify the aasumption. Reverting to § 8, and imagining the difference on percussion to be so slight as to be overlooked, we find that there may be local emphysema or consolidation, and that in either case the expiration may be prolonged, but that the impiration in emphysema tends to softness, in consolidation to harshness; further, that if the voice-sound differ, it is weaker with the prolonged expiration of emphysema, louder with the prolonged expiration of consolidation, than at the corresponding portion of the opposite lung. One important fact simPlifies the inquiry very much : it is this, that if there be no superadded sound in emphy sema, we shall have little or no cough, and no general symptoms: we have therefore only to decide what differenc,e in the results of auscultation is sufficient to determine that the general symptoms are due to commencing consolidation. (1) The most certain indi cation is when on one side the inspiration is shorter and the ex piration longer than on the other. (2) The next in order of dis tinctness is when the inspiratory sound is wavy or jerking while it is even and continuous on the opposite side. (8) When both sounds am longer and louder on one side, the indication is only trustworthy if they be also harsh and unnatural there ; or, when this exaggeration is confined to the left side, for on the right side they are often louder in perfect health. (4) Expiration heard only on one side when no other change is observed, is a suspicious sign. (5) Inspiration heard louder on the left side is also suspi cion& (6) The voice-sound heard louder on the left side along with any of the changes just mentioned is more to be regarded than when heard louder on the right.
When a difference is established by percussion, it is evident that the lungs are in different states, and yet neither may be absolutely healthy ; the same condition may have commenced in one which is advanced in the other. Con siderable experience may be requisite to justify the assertion that both are diseased, but the conclusion may be a correct one, with very imperfect know ledge in the cases referred to in I 1, that there is consolidation on the duller side. The dulness is absolute as well as relative; the breath-sound is changed in rhythm and quality as well as louder, when not obscured by superadded sounds, and the voice-sound points to the same conclusion.
But let us be very careful how we take the next step and determine what that consolidation is. It is of the utmost importance to leave the mind as much unbiassed as possible by the facts elicited by percussion and auscultation in the clavicular region, because the conclusion must rest quite as much upon the history of the case, and upon the evidence derived from other regions of the chest ; and till these are compared together we are not in a position to form any opinion whether the cause of consolidation be tubercles, pneumonia, or pleurisy.
No distinction has been here made between the varieties of blowing sounds, whether diffuse or tubular, bronchial or cavernous. In so far as these names express conditions of lung they are objectionable, and in so far as they express differences of sound they may be of value to us afterwards in deciding what is the actual cause of the consolidation ; but at present it is quite immaterial to our inquiry whether the sound be formed in &large bronchus or in a vomics.
The difference is one of degree, not of kind, and the fact is simply that a blowing sound is heard on that side which is dull on percussion, and we de termine that these two circumstances taken together prove the existence of consolidation.
Dulness on percussion would seem to be opposed to the idea of the lung being hollowed out by cavities : and the conclusion would appear to be not unnatural, that when the breathing is louder from this cause, the resonance on percussion ought to be greater than on the opposite side. Such, however, is not usually the case, and it is only to be observed when a large cavity exists near the surface : the percussion sound then presents the characters of wooden hollowness (of this kind is the cracked-pot sound) ; and an expert auscultator can by percussion alone feel pretty certain regarding the causes of such dif ferences : the student mu it be content at first with the broad distinctions of increased and diminished resonance and resistance. The long blowing breath sound heard with a tumor on one side of the chest, is to be accounted for by its pressing on some large bronchus on careful auscultation it will be noticed that this sound is heard in addition to, not instead of, the vesicular breathing; the latter, however, is weaker than on the healthy aide.
When remarkable resonance is heard, as referred to in 2, it is to be noted first whether this be general or local ; and next whether the sound represent merely a great exaggeration of the natural sound with complete resiliency, or have acquired any peculiar or tympanitic tone, and whether it be accompanied by a sense of resistance: the examination of the posterior part of the chest will readily clear up any doubt between a large cavity and a condition of pneumothorax ; it will equally answer the question as to the presence of fluid in the pleura and of emphysema in the marked form to which this section refers : the possible contingency of a small portion of air occupying the upper part of the pleura is best solved by the history of the case. It is very rarely met with except after the operation of paracentesis ; but it probably does sometimes occur from spontaneous decomposition of the purulent fluid of empyema.
The cases ranged under a 3 are those most likely to be confounded together by a learner: his ear is sufficiently educated to know that there is a difference on percussion, but he may mistake the sharpness of the tone of slight con solidation for an increase of resonance. It is a good plan to compare not only the opposite sides of the chest, but also the upper and lower parts of the same side, when it will at once be perceived that there is a greater difference between the resonance above and below on the duller side than on the more resonant one : for this indication to be conclusive, the chest must be symmetrical. Still, the fact does not determine which lung is the seat of disease, and the first impression is very probably that it must be on the duller side, when in reality it is perhaps on the more resonant one. The safest course to pursue in all possible cases of doubt is to compare the whole auscultatory pheno mena, not only as heard at corresponding portions of opposite lungs, but as heard in different parts of the same one : we may conclude with pretty great certainty that if under either clavicle they deviate much from their general character throughout the rest of the chest, there disease of some sort exists; and whether that be of the form of consolidation or of dilatation is to be re solved by the fact that comparative dalness and increased voice-sound (which always to, a certain extent go together) are found on the healthy side when the disease is emphysema, on the diseased side when it is tubercular. The presence of a dilated bronchus in the emphysematous lung, causing blowing breath-sound, cannot so readily mislead us in this as in the following section, where the result of percussion is negative : in this case the absence of dulness or want of resiliency should be sufficient to guard against error.