938 A MANUAL OF ANATOMY 



to be reflected on to the diaphragm. The right pleura pursues an 

 undeviating course downwards behind the sternum as far as the 

 junction of the body and ensiform process. At this level it leaves 

 the bone, and passes obliquely outwards, downwards, and back- 

 wards over the inner surface of the seventh costal cartilage, from 

 which it is reflected on to the diaphragm. 



Costo-diaphragmatic Reflection. — The level of this reflection may be 

 considered in the first place as it affects certain definite vertical 

 lines. In the left sternal line it takes place at the level of the 

 sixth costal cartilage, and in the right sternal line at the level of 

 the soventh costal cartilage. In the left mammary line it takes 

 place at the level of the eighth costal cartilage, where it joins the 

 osseous part of the rib, and on the right side at a similar level. In 

 the left mid-axillary line it takes place on a level with the lower 

 border of the tenth rib, this being the lowest point to which the 

 pleura descends. In the right mid-axillary line it takes place on 

 a level with the upper border of the tenth rtb, or, it may be, the 

 lower border. Posteriorly, in the scapular line (inferior angle of 

 the scapula), on each side, it takes place at the level of the lower 

 border of the twelfth rib. From this point inwards to the vertebral 

 column the line of pleural reflection is a little below the adjacent 

 border of the twelfth rib, and is very nearly midway between the 

 vertebral end of that rib and the first lumbar transverse process. 



From the foregoing description it will be evident that the pleura 

 descends lowest in the mid-axillary line, and that posteriorly, 

 close to the vertebral column, it actually descends below the level 

 of the lower border of the twelfth rib. The direction of the line of 

 costo-diaphragmatic reflection, from before backwards, is at first 

 obliquely downwards and outwards, until the level of the tenth rib 

 is reached. Thereafter the line passes backwards and upwards to 

 the vertebral column. The costo-diaphragmatic pleural line is on a 

 distinctly lower level than the margin of the base of the lung, but it is 

 a little above the line of the costal attachment of the diaphragm. The 

 portion of the diaphragm below the line is therefore in direct contact 

 with the thoracic wall and adjacent internal intercostal muscles, 

 without the intervention of the pleura, and the costo-diaphragmatic 

 reflection is connected to these structures by a fascial expansion. 



The free surfaces of the parietal and visceral pleurae are, in health, 

 in close contact. They are polished and moistened by a slight 

 amount of serous fluid, so that they glide smoothly upon each other. 

 In cases of pleurisy, however, certain changes take place. The free | 

 surfaces are, in the first place, rendered dry, and thereafter theyj 

 become roughened at intervals by the deposit of lymph. Under 

 these circumstances the movement of the lung is accompanied by, 

 the sound known as pleuritic friction. Adhesions are also frequently | 

 formed, and a serous exudation takes place into the pleural sac,- 

 which tends to compress the lung injuriously, the condition being j 

 known as hydro-thorax. In cases of serous exudation the cavity of j 

 the pleura, which is a shut sac, is clearly demonstrable, but in 'I 



