234 SPECIAL ANATOMY. 



d. The lymphatics, superficial, are very numerous j a trunk also passes out 

 from the interior of the lung at the root ; however, in their interior the rete is 

 not yet sufficiently demonstrated ; they pass into the gl. bronchioles and tra- 

 cheales, which become black between the tenth and twentieth year. 



e. Nerves: branches of N. vagtis and (a few) of N. sympathicus form a plexus 

 pulmonalis anterior, which spread upon the bronchia in the interior, and a pos- 

 terior which go to the larger branches of the Bronchi. 



f. Interlobular uniting tissue, consists of fine fibres which surround the 

 vesicles in thin, the lobules in rather thicker lamina?, containing no fat, but 

 with time on the surface of the lung the colouring matter which produces the 

 black spotted appearance. 



Function of the Lungs. The change of the venous into arterial 

 blood, effected by the inspiration of atmospherical air, and excre- 

 tion of carbonic acid, resulting from expiration. 



468. 4. The Pleurx, Sacci pleurse, 



are two closed serous sacs, one of which covers each lateral half 

 of the thoracic cavity, and then the lung. We distinguish : 



a. Pleura costalis, that is, the part which loosely attached to 

 the internal surfaces of the ribs and mm. inter cost ales, extends 

 from the border of the sternum to the sides of the dorsal vertebra, 

 covering before the vasa mammaria, behind (before the heads of 

 the ribs) the ganglia n. sympathici, and projecting above over 

 the first rib and the apex of the lung. 



b. Pleura phrenica passes off below from the pi. costalis, 

 firmly attached to the superior surface of the diaphragm, and by 

 a triangular fold, lig. pulmonis, with the posterior border of the 

 inferior lobes of the lungs, and with the pulmonary veins. 



c. Mediastinum, is that part of the Pleura which is reflected 

 before from the borders of the Sternum, behind from the sides of 

 the dorsal vertebra upon the roots of the lungs, whereby a medi- 

 astinum anticum and posticum arises. The anterior mediastinum 

 is different on both sides; the right, for instance, commences 

 above from the right border of the m.anubrium; below from the 

 centre, indeed from the left border of corpus sterni ; the left, from 

 the left border of manubrium sterni, and below from the external 

 extremity of the sixth and seventh rib cartilages. Between the 

 two anterior and the two posterior mediastina an X shaped space 

 remains, cavum mediastini, which is divided by the heart (or, as 

 the French describe it with greater accuracy, by the roots of the 

 lungs), into an anterior and posterior. 



1. Cavum mediastini antici, is bounded before by the Sternum and the left 

 rib cartilages, laterally by the two anterior mediastini, behind by pericar- 

 dhvm, the great vessels, and above by the trachea. Above narrow and 

 vertical, below sloping arid directed towards the left ; it contains : 



the Thymus gland [or its remains], nn. phrenici, glandul. mediastini 



