In percussing the supra-spinous fossm it is very necessary to see that the muscles of the shoulders are equally relaxed on both sides. Elevation of the shoulder, or a cramped position contracting the muscles of one side, will modify the percussion note and make the sound more or less dull, al though the lung is perfectly healthy. If an infant be placed in his nurse's arms iu the position already described, and an older child be made to sit with arms folded, shoulders depressed, and back slightly bowed, the re sults of percussion may be depended upon. Too much stress should not be laid upon slight differences between the two sides. A temporary col lapse of the air-cells at the apex is not uncommon from imperfect expan sion of this part of the lung, and therefore slight dulness noticed at one visit may on the next have completely disappeared. There is also a spe cial source of error in percussing the posterior bases of the lungs in chil dren which it is important to be aware of. In young subjects the liver is relatively large, and rises higher on the right side of the chest than it does in older persons. There is therefore normally a certain dulness of percus sion in the right infra-scapular region. This dulness is more extensive in some healthy children than it is in others. We may recognise the cause of the modified note by remarking that the breath-sounds at this point, although weak, are perfectly healthy.
Special varieties of the percussion note have little or no diagnostic value in young subjects. The tubular (or tracheal) note is often obtained in various states of the lung-tissue, and is not characteristic of any special condition. The "cracked-jar " note is a natural phenomenon in early life if the yielding chest be percussed during expiration or when the mouth is open.
In auscultation of the chest, however young the child, the stethoscope should always be used. This instrument is even of greater value in the young subject than it is in the adult, for the chest being smaller, it is more important to limit as narrowly as possible the area under investigation. I have rarely known children object to its employment if the instrument had been first placed in their hands and spoken of as "a trumpet." Indeed, the use of this familiar word usually awakens their interest and actually facilitates the examination.
In the normal state the breath-sounds are coarser and harsher (puerile respiration) than they become in older persons, and this harshness in cer tain patients is so pronounced that it is not unfrequently mistaken by an inexperienced observer for a sign of disease. The harsh character of the breath-sound is especially marked at the apices, and the expiration at this part of the lung is often prolonged without the peculiarity being an abnor mal phenomenon. Conduction of sounds from the pharynx and trachea
to the apices is especially common, and it is not rare to find the respira tion at the supra-spinons fosses curiously loud and hollow or blowing, although the lungs are healthy. This hollow breathing is no doubt con ducted from the throat. It is often a sign of enlargement of the bron chial glands, these bodies forming a medium of communication between the windpipe and the wall of the chest. It may be heard, however, in cases of enlarged tonsils, and is sometimes present, while the mouth is closed, in children in whom no other morbid condition of any kind can be discovered. In such cases it is greatly modified in character when the mouth is open. The source of this variety of blowing breathing can usually be detected by noticing that it is heard equally plainly at both apices, is chiefly marked in expiration, and is accompanied by no rhonchal sound or any dulness of the percussion note.
Weakness of the vesicular murmur is much less common as a normal condition than loudness of the breath-sound. It is, however, present in some children as an individual peculiarity. If general over both sides, it is a sign of no importance. If limited to particular spots, it is of greater moment, and when noticed at the base of one side should not be disre garded. It may be an early sign of pleurisy or may indicate collapse. At the apices it often arises from insufficient expansion of lung-tissue, and may be of trifling consequence. In such a case it usually passes off quickly, and at the next examination may no longer be detected.
The readiness with which sounds are conveyed from one part of the chest to another is a common source of error. Thus, sounds generated at the base of one lung may often be plainly heard at the corresponding part of the other and healthy lung. In cases of dilated bronchus from fibroid induration it is not uncommon to find cavernous breathing with metallic gurgling rhonchus at both posterior bases—on the sound as well as on the affected side. So, also, a subcrepitant rile developed in one lung may be plainly heard on the opposite side, perhaps over the site of a loculated pleurisy or collapsed lobe, and give rise to much perplexity. In these cases the origin of the transmitted sound can usually be detected by noticing that the quality and pitch of the conducted breath-sound or rille are exactly that heard on the affected half of the chest, only diminished in intensity; the sound is identical in character but weaker in force. This is rarely if ever the case with sounds generated spontaneously in two different spots.