I2 4 



THORAX 



third left costal cartilage to the lower border of the sternal 

 end of the sixth right cartilage indicates the anterior part 

 of the coronary sulcus. The points indicating the positions 

 of the arterial and atrio-ventricular orifices must be placed 

 immediately below the line of the coronary sulcus in the 

 following order from above downwards : pulmonary orifice, 

 aortic orifice, mitral orifice, tricuspid orifice. The centre of the 

 pulmonary orifice is posterior to the third left costal cartilage 



Trachea 



FIG. 62. Drawing of a Stereoscopic Skiagraph of the Trachea and Bronchi 



injected with starch and red lead. 



at the margin of the sternum, The aortic orifice lies 

 posterior to the left half of the sternum opposite the third inter- 

 costal space. The mitral orifice is posterior to the left border 

 of the sternum at the level of the fourth left costal cartilage ; 

 and the centre of the tricuspid orifice is posterior to the middle 

 of the sternum at the level of the fourth intercostal spaces. 



The Thoracic Portion of the Trachea. The thoracic 

 portion of the trachea, like the cervical portion, is a wide 

 tube kept constantly patent by a series of curved cartilaginous 

 bars which are embedded in its walls. The bars are 



