DISSECTING MANUAL. 



intercostal spaces; and diaphragmatic, lying on the dia- 

 phragm. The visceral glands consist of the following groups: 

 anterior mediastinal, lying in the anterior mediastinum; su- 

 perior mediastinal, surrounding the innominate veins along 

 the upper part of the aortic arch and in front of the trachea; 

 posterior mediastinal, surrounding the aorta and oesophagus; 

 and bronchial, surrounding the bronchi. [923] 



Thoracic Duct. Beginning in a dilatation .(receptaculum 

 chyli) opposite the first two lumbar vertebrae, this ascends 

 through the aortic opening of the diaphragm and on the front 

 of the spine to the root of the neck, lying to the right of the 

 midline below the fifth dorsal vertebra, and to the left above 

 this. Then running outward between the vertebral and carot- 

 id arteries it joins the commencement of the left innominate 

 vein. It is about eighteen inches long, thin-walled, of varying 

 but small diameter ; it lies in front of the small azygos veins, 

 behind the oesophagus. [906] 



Right Lymphatic Duct. This is a short trunk draining the 

 right upper half of the body ; it descends along the inner bor- 

 der of the Scalenus anticus and ends in the right innominate 

 vein. [909] 



THE RESPIRATORY SYSTEM. 



Trachea. Beginning at the lower border of the cricoid, this 

 descends in the midline in front of the oesophagus and spine; 

 it finally deviates slightly to the right, and at the upper border 

 of the fifth dorsal vertebra divides into the two bronchi; it is 

 slightly dilated near its middle. It consists of a fibre-elastic 

 tube containing from fifteen to twenty cartilaginous rings 

 which are deficient behind; the lowest ring inclines downward 

 anteriorly in a median peak, from which a strip runs backward 

 between the bronchi. Within it posteriorly a layer of trans- 

 verse involuntary muscle bundles (Musculus trachealis), on 

 the posterior aspect of the inner surface of the trachea, con- 

 nects the ends of the rings. [972] 



[136] 



