The condition just described is that of the fully-developed dis ease : but the practitioner may have to treat a case in an earlier stage, when the history is such as leads him to suspect inflamma tion of the lung, while yet there is no evidence of consolidation. He only finds that on one side the breathing is weaker than on the other, and then undoubtedly fine crepitation is among the surest and the earliest indications of what is going to happen ; but while he fails in no part of the treatment which the general condition of the patient and the probability of the invasion of pneumonia would indicate, it is wise to abstain from a positive diagnosis until the signs be more fully developed, in order that he may not be misled in his judgment of subsequent symptoms, which may prove the disease to be something else, bronchitis or pleurisy, for example.
It must be remembered, too, that when pneumonia is deep seated, its presence will scarcely be marked by any physical signs at all; but if sufficient regard be paid to the whole e,ategory of symptoms, we may be contented if the diagnosis derive confirma tion from superficial weakness or deficiency of breathinq, with local exaggeration of voice-sound, especially when these indica tions are met with at the side of the chest, at a distance from the large tubes, while percussion elicits no dulness, and auscultation detects no crepitation. In either of the,se cases the practitioner, by causing the patient to cough, or even only to talk, and thus se,curing deep inspiration, may develop the absent phenomenon of crepitation. One form of pneumonia in particular belongs to this class ; it is that dependent on secondary suppurative fever with pyEemia. The small foci of purulent pneumonia are rarely to be discovered by auscultation ; and the supervention of cough, with any alteration in the breath-sound on one side of the chest, is enough to show that secondary suppuration has attacked the lung : but here the question of which organ is attacked is merged in the more important one of a general crasis of the blood, indicated by the symptoms of suppurative fever.
The great error of physical diagnosis, in asserting that fine crepitation is pathognomonic of pneumonia, has been already mentioned. It may be quite true that there is one form of it which is never heard in any other condition of disease (yet even this may be exactly simulated by coarse friction-sound); it may be also true that, if this form be clearly and distinctly heard, pneu monia is certainly present; but if we take all the varieties of crepitation into account which we do hear in true pneumonia, they are clearly not confined to it. It is equally false to assume that crepitation is a certain indication of
pneumonia, and that its absence proves the disease to be of some other kind.
The real value of crepitation is only as it confirms or is opposed to other signs of disease : when no other symptoms of pneumonia accompany its pre sence, we must seek for some different explanation of the phenomenon ; its entire absence may lead us to suspect that we have been wrong in attributing other symptoms to pneumonia; but if that evidence be distinct, its degree of coarseness need not be regarded ; nay, even when the character of the sound is entirely altered, and accompanies expiration as well as inspiration, it still does not stultify the diagnosis of pneumonia, but only shows that an unusual amount of serous exudation has taken place—a fact which the character of the expectoration will probably sufficiently ratify.
Pneumonia is most frequently found in the lower lobes, and we consequently place most reliance upon the auscultatory pheno mena when observed in that situation ; we receive their evidence with more hesitation when confined to the upper lobe; and when the whole lung presents the same character of dulness, blowing breathing, and crepitation, we may be certain that, unless the general symptoms be very grave indeed, the disease is partly, if not wholly, tubercular.
In distinguishing fibrinous from tubercular deposit in the upper lobe, we must remember that very fine crepitation is rarely met with at the upper part of the lung : consequently, the more con tinuous the sound appears, the more distinct its limitation to the inspiration alone, and the more equal its diffusion over a con siderable space, the more probably it is caused by pneumonia. We have first to take into consideration the history of the case, the duration and general symptoms of the disease, and the cha racter of the sputa; and next, to remember that, in such a situa tion, if the parenchyma be infiltrated with lymph, dulness must necessarily be very marked; the vesicles are occluded, and the vesicular murmur will therefore be annihilated; the tubes remain open, are inflamed and indurated, and the breathing will conse quently be very loud and whiffing, and the voice-sound brassy, and much increased in intensity. It will also be remarked that these changes are pretty equally extended to the whole lobe of the lung, and its margin pretty clearly defined by their extent, because they are often more marked towards its lower part than quite at the apex.