

THE LUNGS AND PLEUE^E. 



1401 



vertically above the angle of the tenth costal cartilage ; from that point the line is 

 carried, with a slightly downward curve, across the lateral aspect of the chest to 

 the twelfth rib at the lateral margin of the sacro-spinalis ; thence it passes below 

 the twelfth rib and reaches the vertebral column at the level of the superior border 

 of the twelfth thoracic spine. The relation of the costo-diaphragmatic reflection 

 to the seventh, eighth, and ninth costal arches may be conveniently expressed by 

 stating that it lies a little in front of the costo-chondral junction of the seventh, 

 opposite that of the eighth, and a 

 little behind that of the ninth. 



The left costo-diaphragmatic re- 

 flection is indicated by a line drawn 

 from a point opposite the sixth 

 costal cartilage, a finger's breadth 

 from its junction with the sternum, 

 to a point one and a half inches 

 vertically above the angle of the 

 tenth costal cartilage, and thence 

 to the vertebral column, as on the 

 right side, but at a slightly inferior 

 level. 



The costo-diaphragmatic re- 

 flection reaches its lowest limit a 

 little behind the mid-axillary line 

 two inches vertically above the tip 

 of the eleventh costal cartilage, a 

 level which may be readily in- 

 dicated, according to Cunningham, 

 by a point in the mid-axillary line 

 intersected by a horizontal line 

 drawn round the trunk at the 

 level of the lowest part of the ex- 

 tremity of the first lumbar spine 

 (Fig. 1092). The same author 

 localised the level of the dia- 

 phragmatic pleural reflection in 

 the mammary line at the point 

 where this line is intersected by 

 another horizontal line at the level 

 of the spine of the last thoracic 

 vertebra. 



The relations of the pleura to the 

 twelfth rib are of importance to the 

 surgeon, especially in connexion with 

 operations on the kidney (Figs. 1094 

 and 1095). When this rib is not 

 abnormally short, the pleural reflec- 

 tion crosses it opposite the lateral 

 border of the sacro-spinalis muscle ; 

 hence an incision may be carried 

 deeply as far as the apex of the angle 

 formed by the twelfth rib and the 

 lateral border of the sacro-spinalis 



without entering the pleura. When, however, the twelfth rib does not reach the lateral 

 border of the sacro-spinalis, an incision carried upwards into the apex of the angle between 

 this muscle and the eleventh rib is certain to wound the pleura (Melsom). It is im- 

 portant, therefore, to count the ribs from above downwards, in order not to mistake the 

 eleventh for the twelfth, when the latter is rudimentary. 



Medial to the lateral edge of the sacro-spinalis the pleural reflection lies below the 

 level of the twelfth rib, and not infrequently descends as far as the transverse process 

 of the first lumbar vertebra. 



FIG. 1093. LATERAL VIEW OF THE EIGHT PLEURAL SAC IN 

 A SUBJECT HARDENED BY FORMALIN INJECTION. The blue 

 lines indicate the outline of the right lung, and also the 

 position of its fissures. (From Cunningham.) 



