2'42 



LIMITS OF THE LUNGS. 



moves an index, whose excursions are indicated on a circle with a scale attached 

 to it. 



The Cyrtometer of 



Woillez is very useful. A 

 brass chain, composed of 

 movable links, is applied in 

 a definite direction to part 

 of the chest-wall, e.g., trans- 

 versely on a level with the 

 nipple, or vertically upon 

 the mammillary or axillary 

 lines anteriorly. There are 

 freely movable links at two 

 parts which permit the chain 

 to be easily removed, so that 

 as a whole it still retains its 

 form. The chain is laid 

 upon a sheet of paper, and 

 a line drawn with a pencil 

 around its inner margin gives 

 the form of the thorax (Fig. 

 107). 



Fig. 108. 

 Sibson's Thoraco-meter. 



Limits of the Lungs. The extent and boundaries of the lungs are 

 ascertained in the living subject by means of Percussion, which consists 

 in lightly tapping the chest- wall by means of a hammer (percussion- 

 hammer). A small ivory or bony plate (pleximeter), held in the 

 left-hand, is laid on the chest, and the hammer is made to strike this 

 plate, whereby a sound is emitted, which sound varies with the con- 

 dition of the subjacent lung-tissue. Wherever the lung substance in 

 contact with the chest-wall contains air, a clear resonant tone or sound 

 such as is obtained by striking a vessel containing air, a clear 

 percussion sound is obtained. Where the lung does not contain air, 

 a dull sound like striking a limb is obtained. If the parts containing 

 air be very thin, or are only partially filled with air, the sound is 

 "muffled." 



Fig, 109, along with Fig. 31, indicate the relations of the lungs to 

 the anterior surface of the chest. The apices of the lungs reach 3-7 

 centimetres (I'l 2'7 inches) above the clavicles anteriorly, while 

 posteriorly they extend from the spines of the scapula as high as the 

 seventh spinous process. The lower margin of the right lung in the 

 passive position (moderate expiration) of the chest, commences at the 

 right margin of the sternum at the insertion of the sixth rib, runs under 

 the right nipple, nearly parallel to the upper border of the sixth rib, 

 and descends a little in the axillary line, to the upper margin of the 

 seventh rib. On the left side (apart from the position of the heart), the 

 lower limit reaches as far down anteriorly as the right. In Fig. 109 

 the line, a, t, 6, shows the lowest limit of the passive lungs. Posteriorly, 



