NORMAL RESPIRATORY SOUNDS. 1 79 



and especially in emphysema, where the air- vesicles of certain parts of the lung (apices and 

 margins) become greatly dilated. 



The pitch of the percussion -sound ought also to be noted. It depends upon the greater or 

 less tension of the elastic pulmonary tissue, and on the elasticity of the thoracic wall. The 

 tension of the elastic tissue is increased during inspiration and diminished during expiration, so 

 that even under physiological conditions, the pitch of the sound varies. 



The sound is said to be tympanitic when it has a musical quality resembling in its timbre 

 the sound produced on drums, and when it has a slight variation in pitch. If a caoutchouc 

 ball be placed near the ear, on tapping it gently, a well-marked tympanitic sound is heard, and 

 the sound is of higher pitch the smaller the diameter of the ball. A tympanitic sound is 

 always produced on tapping the trachea in the neck. A tympanitic sound produced over the 

 chest is always indicative of a diseased condition. It occurs in cases of cavities or vomicae within 

 the substance of the lung, (the sound becomes deeper when the mouth, or better, the mouth 

 and nose, are closed), when air is present in one pleural cavity, as well as in conditions where 

 the tension of the pulmonary tissues is diminished. The tympanitic sound resembles the 

 metallic tinkling which is heard in large pathological cavities in the lungs, or which occurs 

 when the pleural cavity contains air, and when the conditions which permit a more uniform 

 reflection of the sound-waves within the cavity are present. 



[When a cavity, freely communicating with a large bronchus, exists in the upper and 

 anterior part of the lung, a peculiar "cracked-pot sound" is heard on percussing over the 

 part. Some notion of this sound may be obtained by clasping the two hands so as to bring the 

 palms nearly together, leaving an air-space between, and then striking them on the knee. 

 When percussion is made over a large cavity communicating with a bronchus, some of the air is 

 expelled, and the sound thereby emitted is blended with the fundamental note of the air in the 

 cavity itself, the combination of these two sounds thus producing the " cracked-pot" sound.] 



Resistance. When percussing a chest, we may determine whether the substance lying under 

 the portion of the chest under examination presents great or small resistance to the blow, either 

 of the percussion-hammer or of the tips of the fingers, as the case may be, [e.g., in great 

 pleuritic effusion exerting much pressure on, and so distending, the thoracic walls]. 



Phonometry. If the stem of a vibrating tuning-fork be placed on the chest-wall over a part 

 containing air, its sound is intensified ; but if it be placed over a portion of the lung which con- 

 tains little or no air, its sound is enfeebled (von Baas). 



116. THE NORMAL RESPIRATORY SOUNDS. If the ear directly, or 

 through the medium of a stethoscope, be placed iu connection with the chest-wall, we 

 hear over the entire area, where the lung is in contact with the chest, the so-called 

 ;< normal vesicular sound," which is audible during inspiration, and its typical 

 characters may be studied by listening in the infra-scapular region in an adult. It 

 is a fine sighing or breezy sound, [which gradually increases in intensity until it 

 reaches a maximum, and falls away before expiration begins]. It is said to be 

 caused by the sudden dilatation of the air-vesicles (hence " vesicular ") during inspira- 

 tion, and it is also ascribed to the friction of the current of air entering the alveoli. 

 The sound has, at one time, a soft, at another, a sharper character ; the latter occurs 

 constantly in children up to 12 years of age. In their case, the sound is sharper, 

 because the air, in entering vesicles one-third narrower, is subjected to greater fric- 

 tion. This is followed by an expiratory sound, which may be absent during quiet 

 breathing. It is a feeble sighing sound, of an indistinct soft character, caused by 

 the air passing out of the air-vesicles, is three or four times shorter than the 

 inspiratory, is loudest at first, and soon disappears, the latter part of the expiratory 

 act giving rise to no audible sound. Its absence is not a sign of disease, but when 

 it is prolonged and loud, suspicion is aroused.] 



Bronchial Respiration. Within the larger air-passages larynx, trachea, bronchi 

 during inspiration and expiration, there are loud, rough, harsh sounds like a 

 sharp h or ch the " bronchial " the laryngeal, tracheal, or " tubular" sound, or 

 breathing. [In normal bronchial breathing, as heard over the trachea, there is a 

 pause between the inspiratory and expiratory sounds, which are of nearly equal 

 duration and of about the same intensity throughout. These sounds are also heard 

 between the scapulae, at the level of the fourth dorsal vertebra (bifurcation of 

 trachea), and they occur also during expiration, being slightly louder on the right 

 side, owing to the slightly greater calibre of the right bronchus. At all other parts 



