170 THE BODY AT WOEK 



ear and the great tracheal or bronchial tubes ; and the pul- 

 monary murmur, heard over all regions where the bronchi 

 are buried in lung. Healthy lung is as bad a conductor of 

 sound as a sponge or a wad of cotton-wool. The laryngeal 

 murmur is inaudible in regions in which lung lies beneath the 

 chest- wall. It would be far beyond the scope of this book to 

 attempt to describe the very varied alterations in the chest- 

 sounds which may be produced by disease. The student would 

 do well to familiarize himself with the nature of the sounds 

 which are heard in health, and the situations in which they are 

 heard, in order that he may be able, in abnormal conditions, 

 to recognize that something is wrong. 



The chief departures from the normal may be grouped under 

 the following heads : (1) The pulmonary murmur may lose its 

 soft, smooth, sighing character owing to inflammation of the 

 alveoli and infundibula. It may be as loud in expiration as 

 in inspiration. Only a practised ear can estimate the signifi- 

 cance of these changes. (2) The laryngeal murmur may be 

 reinforced by " rales " a convenient term for supplementary 

 sounds. The source of such rales may be a cold in the chest, 

 laryngitis, or bronchitis of various degrees. (3) The laryngeal 

 murmur may be heard in situations in which lung intervenes 

 between the ear and the larger bronchial tubes. This can be 

 due only to the lung being in an abnormal condition as a con- 

 ductor of sound. Instead of being as spongy as well-made 

 Vienna bread, its air-spaces are filled with solid or fluid deposit. 

 It is as firm as dough. To such a condition it attains at the 

 height of pneumonia a stage termed " hepatization " because 

 in section it looks like liver rather than lung. 



Breathing is the enlargement and diminution of the chest, 

 which causes air to be drawn into and expressed from the 

 lungs. The windpipe being open, the air inside the lungs is, 

 of course, at the same pressure as the atmosphere. Expansion 

 of the chest results in the equal expansion of the lungs. Since 

 there is no air-space between the outer surface of the lungs 

 and the inner surface of the chest-wall, the lungs cannot 

 separate from the chest- wall when it expands. But the lungs 

 contain elastic tissue always slightly on the stretch. If the 

 chest be punctured, and air admitted between the chest-wall 

 and the lungs, the lungs collapse. The expiratory movement, 



