THE VISCERA. 233 



4. The posterior border is broad, obtuse, and lies at the side of 

 the vertical column. 



5. Basis is hollowed out, rests upon the (convex) diaphragm ; 

 its posterior border reaches deeper downwards than the anterior, 

 almost as far as the inferior surface of the liver. 



6. Apex, is round, and projects (one inch) upwards above the 

 first rib. 



The left lung is narrower and lighter, but longer than the right 

 (on account of the heart) ; has one fissure (incisura) and two 

 lobes, a larger superior, a smaller inferior. 



The right lung is less (in the vertical diameter, on account of 

 the liver), but broader; has two indsurse and three lobes ; the 

 larger superior, the smaller inferior, and the smallest central lobe. 



Parenchyma of the lungs. The spongy and soft tissue of the 

 lung is very strong, elastic, crepitates under the pressure of the 

 finger when respiration has been once performed, and consists of 

 the following parts : 



a. Aeriferous vessels, vasa aerofera. After the Bronchi have divided 

 many times (always at an acute angle), the small branches (bronchia) lose 

 the regular structure of the larger ; the cartilages on the anterior wall are no 

 longer in the shape of the letter C, but irregular, and are finally entirely 

 lost, like the muscular fibres, until at last vesicles w r ith roundish corners, and 

 terminating in a cul-de-sac, vesiculce pulmonales s. cellules a'ercee (of one-sixth to 

 one-sixteenth of a line), remain, which consist of mucous membrane and 

 thin longitudinal fasciculi of uniting tissue. The pulmonary vesicles open 

 into a common canal, to which they hang like berries upon their stalks 

 (as in glands), and form a pulmonary lobule (lobulus). The pulmonary 

 lobules are again associated in one great canal into a lobe (lobus), and are, 

 like these, isolated from one another by the serous membrane which forms 

 their envelope. 



b. Pulmonary vessels, vasa pulmonalia. 1. Art. pulmonalis ramifies with 

 the branches of the bronchi, and surrounds the lobuli with a large circle of 

 capillary vessels, and the pulmonary vesicles with a smaller and more deli- 

 cate rete (of O02 to 0-06 of a line diam.), between the meshes of which the 

 vesicles lie, so that through the thin wall of both the inspired air (in the 

 vesicles) comes into immediate relation with the venous blood (in the arte- 

 ries) and changes it into bright red, arterial blood, which through : 2. Vv. 

 pulmonales flows back again into the heart. Two pulmonary venous branches 

 (to each branch of the pulmonary artery) arise from the capillary rete of the 

 art. pulmonal. and bronchialis. 



c. Bronchial vessels, vasa bronchialia. 1. Artt. bronchiales do not pass to 

 the pulmonary vesicles, but to the walls of the bronchia, art. pulmonalis, to the 

 Bronchial glands, to the uniting tissue between the lobules and the pleura; 

 they serve for the nourishment of, and for secretion in, these parts ; they arise 

 from the Aorta thoracica and mammaria interna, and frequently anastomose 

 with A. pulmonalis: passing into the commencements of w. bronchiales, but 

 also the w. pulmonales. 2. J'v. bronchiales open inside the lung into the J'v. 

 pulmonales: outside, upon the right side into ven. azygos, upon the left side 

 into Ven. intercostal, superior. 



