THORAX 



lies opposite the fibro-cartilage between the second and third 

 thoracic vertebrae, whilst the lower end of the body of the 

 sternum corresponds in level with the middle of the body of the 

 ninth thoracic vertebra. The bodies of the thoracic vertebrae 

 project anteriorly into the cavity of the thorax, and greatly 

 diminish its antero-posterior diameter in the median plane ; 

 but the backward sweep of the posterior portions of the ribs 

 produces a deep hollow on either side of the vertebral column, 

 for the reception of the most massive part of the lung. 



The superior aperture, inlet of the thorax, is a narrow 

 opening which is bounded by the first thoracic vertebra, the 



Right vagus nerve 



Right 

 subclavian artery 



Trachea 



CEsophagus Left subclavian artery 



Stilcus subclavius 



innominate vein 



Left vagus nerve 



Left 



common 



Carotid 



Left 



innomina: 



vein 



FIG. i. Cervical Domes of the Pleural Sacs, and parts in relation to them. 



first pair of costal arches, and the manubrium sterni. The 

 plane of this opening is very oblique ; it slopes from the first 

 thoracic vertebra anteriorly and downwards. Through the 

 inlet of the thorax the apices of the lungs project upwards 

 into the root of the neck, and, between them, the follow- 

 ing structures pass through it : the windpipe, the gullet, the 

 vagi, the phrenic nerves, the left recurrent nerve, the ganglion- 

 ated sympathetic trunks, the thoracic duct, and the great 

 arteries and veins which carry blood to and from the head 

 and neck and the upper limbs. 



The base or inferior end of the thorax is very wide, 

 and is sometimes called the outlet. Anteriorly it is bounded 

 by the xiphoid process, and posteriorly by the twelfth thoracic 

 vertebra. Between these points the lower margin of the 

 thorax presents a curved outline. Starting from the sternum, 

 it passes downwards, laterally, and posteriorly, as far as the 

 tip of the eleventh costal cartilage ; thence it proceeds up- 



