Bronchial, blowing and cavernous breath-sounds are produced in chil dren by the same mechanism which gives rise to them in the adult, and correspond to much the same conditions. In the child, however, peculiar ities iu this respect are sometimes noticed. The morbid quality conferred upon the breath-sound is often a step in advance of that heard under similar conditions in the adult. Thus, cavernous breathing is more often a sign of mere solidification of tissue, and is frequently present when the lung is compressed by pleuritic effusion. So, also, the amphoric breath sound with tinkling resonance of the voice or cough is almost always the consequence of a large cavity or great dilatation of a bronchus. It is heard in cases of phthisis, of cirrhosis of the lung, or of subacute catarrhal pneumonia. Pneumothorax, to which cause it is almost solely owing in the adult, is a very rare condition in the child, and the morbid sign can seldom be attributed to this cause.
Although the auscultatory sounds are frequently magnified in the child, it sometimes happens that the contrary condition is found. A patch of consolidation, if covered by a layer of healthy lung-tissue, may give rise to no dulness or alteration of breath-sound, and a bronchophonic reson ance of the voice and cry may be the only sign which betrays its existence.
In crying infants the intensified vocal resonance is an important test of consolidation. If the resonance have an gophonic quality it is character istic of moderate effusion.
The examination of the chest should always be as complete as possible. It is not enough merely to examine the posterior part of the thorax, trust ing that if this be healthy the anterior part is healthy too. A patch of croupous pneumonia or a loculated pleurisy may occupy any part of the lung or chest cavity. Either may be confined to the apex, may lie under one arm, or may be found seated anteriorly or laterally as may as behind. If, therefore the front of the chest is left unnoticed, we may overlook dis ease which closer examination would have discovered. Even if the child cry during the operation, much may still be learned. The cry usually ceases each time the breath is taken in, so that inspiration is audible. Its quality can therefore be ascertained at this time. Moreover, as the chest is expanded deeply after a prolonged crying expiration, the air-cells are fully inflated and few adventitious sounds can escape our notice.