232 SPECIAL ANATOMY. 



Vessels of the Trachea: 1. Artt. tracheaks (from thyreoid. infer.} inferiores 

 (from the Aorta}. 2. The veins of the spaces between the cartilages open 

 into the great trunks along the trachea (on the internal surface), and these 

 into the Vv. thyreoidea infer., mammar., and azygos. 3. The Lymphatics, very 

 numerous, pass into the great lymphatic glands at the bifurcation. 



Nerves : Nn. tracheal. superior, (from ram. recurrens Vagi) ; inferiores (of 

 the trunk of plexus pulmonalis of N. Vagus). 



467. 3. The Lungs, Pulmones, 



are two soft bodies, between which lies the heart, and each of 

 which fills up the lateral half of the cavity of the thorax ; of an 

 irregular, conical shape, internally deeply excavated, with the 

 base directed downwards. Colour: in the adult and aged, greyish 

 blue, traversed by dark blue vessels and bluish black spots, which 

 form polygons, on which account the surface appears marbled ; 

 the posterior surface (generally) a reddish brown. As age" ad- 

 vances, the black spots which lie in the interposed uniting tissue, 

 increase. Weight: In the foetus the lungs, in relation to the body, 

 are as 1 : 60 ; in the adult, 1 : 30. Spec. grav. before birth and 

 respiration : heavier than water ; afterwards : lighter than water. 

 In the male, the lungs are heavier (3 pounds) than in the female 

 (2 1 pounds). 



Each lung is invested by a serous membrane (pleura), and 

 presents : 1. An external, convex surface, which is separated from 

 the ribs by the pleura only, and by a deep fissure, incisura inter- 

 lobularis, into two and three lobes (lobi). The fissure commences 

 behind and above below the apex, and reaches downwards and 

 forwards to the anterior part of the basis of the lung. On the 

 right lung, a second fissure passes upwards and forwards before 

 the termination of the last. 



2. The internal surface, above flat, below excavated, presents, 

 in the centre between basis and apex, and rather towards the pos- 

 terior border, a surface one inch high, a depression half an inch 

 broad (the root, radix, hilus), at which bronchi, arteries, and 

 nerves enter, and veins and lymphatics pass out. Behind the root 

 the internal surface looks towards the vertebral column ; and, on 

 the left side, towards aorta descendens [the lung has a correspond- 

 ing groove], and the superior part of Ductus thoracicus, on the 

 right side, towards V. azygos, cesophagus, and the inferior part 

 of the duct, thoracicus; before the root on the left lung, the left 

 border, the apex of the heart and Aorta descendens; on the right 

 lung, the right auricle of the heart and V. cava superior. 



3. The anterior border is thin, and presents two notches : an in- 

 ferior (to the left for the apex, to the right for the auricle of the 

 heart) ; and a superior (to the left for Art. subclavia, the right for 

 V. cava superior). 



