TOPOGRAPHY OF THE THORAX AND ABDOMEN 9 



external surfaces were taken for the anterior projection 

 (Plate XXVIII), and the most internal portions in the 

 region of the posterior mediastinum (crista pulmonis of 

 Merkel') and the external surfaces for the posterior projec- 

 tion. This difference was made to show the more direct 

 relations of the lungs to the sternum and to the vertebral 

 column respectively. 



The points measured upon any section were located 

 on millimeter cross-section paper, on the horizontal line 

 representing the upper surface of that section, at distances 

 from the zero line equal respectively to their several dis- 

 tances from the midline of the section. In case the plane of 

 the section was exactly horizontal, as in Plate XI, the 

 points so located were points through which the outline of 

 the corresponding organs must pass. But in those cases 

 where the anterior and posterior margins of the section 

 were at different levels, as in Plate VI, correction had to be 

 made for the obliquity of the plane. 



By careful dissections and comparison of the sections, 

 the outline of each organ was made as nearly accurate as 

 possible as to shape and size. When the outlines were 

 penciled in and had been carefully compared with the 

 organs, they were retraced with ink in the broken lines in 

 which they appear in the plates. 



It must be remembered in examining the projections 

 that the cross-lines represent planes which are practically 

 parallel and that the outline of any organ at a given level is 

 as it would appear with the eye in that horizontal plane, and 

 not as it would appear to the eye at any point outside of the 



' Merkel, F., Bardeleben's Handbuch der anatomie. 

 Abthl. 1. 



