THE PLEURA. 



1113 



inserting the knife into it and dividing the two or three upper rings from below upward. If 

 the trachea is to be opened below the isthmus, the incision must be made from a little below 

 the cricoid cartilage to the top of the sternum. 



In the child the trachea is smaller, more deeply placed, and more movable than in the adult. 



A portion of the larynx or the whole of it has been removed for malignant disease, laryng- 

 ict<,m\j. The results which have been obtained from the removal of the whole of it have not 

 been very satisfactory, and the cases in which the operation is justifiable are very few. It may 

 be removed by a median incision through the soft parts, freeing the cartilage from the muscles 

 and other structures in front, separating the larynx from the trachea below, and dissecting off 

 the deeper structure from below upward. 



THE PLEURA. 



Each lung is invested, upon its external surface, by an exceedingly delicate 

 serous membrane, the pleura, which encloses the organ as far as its root, and is 

 then reflected upon the inner surface of the thorax. The portion of the serous 

 membrane investing the surface of the lung is called the pleura pulmonalis 

 (visceral layer of pleura), while that which lines the inner surface of the chest is 

 called the yleiira costalis (parietal layer of pleura). The space between these two 

 lavers is called the cavity of the pleura., but it must be borne in mind that in the 

 healthy condition the two layers are in contact, and there is no real cavity until the 

 lung becomes collapsed and a separation of it from the wall of the chest takes 

 place. Each pleura is therefore a shut sac. one occupying the right, the other the 

 left half of the thorax, and they are perfectly separate, not communicating with 

 each other. The two pleurae do not meet in the middle line of the chest, excepting 

 anteriorly opposite the upper part of the second piece of the sternum a space 

 being left between them, which contains all the viscera of the thorax excepting 

 the lungs : this is the mediastinum. 



Reflections of the Pleura (Fig. 707). Commencing at the sternum, the pleura 

 passes outward, covers the costal cartilages, the inner surface of the ribs and 



TRIANGULARIS STERNI. 



Internal Mammary Vessels. 



Left Phrenic Serve 



Pleura Pulmonalis. 

 Pleura Costalis. 



Vena Azygos Major} Posterior 

 Pneumogastric Ferees > 



FIG. 707. A transverse section of the thorax, showing the relative position of the viscera and the reflections 

 of the uleura:. 



Intercostal muscles, and at the back part of the thorax passes over the thoracic 

 ganglia and their branches, and is reflected upon the sides of the bodies of the 



