THE RESPIRATORY ORGANS LUNGS. 



577 



bronchial subdivisions. They accompany the pulmonary artery, 

 and occasionally the veins and the bronchial arteries. 



3. The interlobular connective tissue of the lungs, everywhere 

 existing very sparingly, is the common areolar, containing in the 

 adult a quantity of blackish pigment in the form of irregular minute 

 granules, aggregations of granules, or crystals, but which are never 

 inclosed in cells. They also frequently exist in the walls of the 

 air-cells themselves (p. 132). 



The pulmonary lobules are far more distinct t in the infant and 

 child than in the adult. In the latter, they are so intimately united 

 that even on the surface of the lung their outlines are but imper- 

 fectly perceived. They are fa to ^ of an inch in diameter. The 

 secondary lobules, however J to 1 inch 

 in diameter are very apparent, being 

 bounded by streaks of pigmentary 

 matter. 



Each lobule is of a more or less 

 conical or pyramidal form, and consists 

 of A, a terminal bronchial tube ; B, 

 the air-cells ; and c, the capillary plex- 

 us; besides the nerves and some con- 

 nective tissue. 



A. The terminal air-tubes are from 



Fig. 402. 



are 



T -J<y to ? J 5 (g^ to 4*0 of an inch Todd 

 and Bowman) of an inch in diameter. 

 They enter at the apex of the lobule, 

 and, passing nearly in its axis, termi- 

 nate in the lobular passages and infun- 

 dibula (the former being 2 to T ^ of 

 an inch in diameter), as shown in Fig. 

 402. The air-cells open into the in- 

 fundibula, and their appearance in the 

 lobule, as seen from without, is shown 

 by Fig. 403. 



B. The air-cells are grouped around 

 and open directly into the infundibula. 

 A few, indeed, open thus into the air- 

 tube before it divides. (Fig. 403.) Thus 

 a honey-comb appearance is afforded 

 by the cells, as seen in their relations 

 37 



Termination of the bronchi in the 

 lung of the dog. a. Terminal tube, and 

 its branches (lobular passages), and the 

 infundibula. b. One of the last. c. Septa 

 projecting inwards on the infundibular 

 wall, and forming the alveoli or cells. 

 (From Rossignol.) 



Fig. 403. 



Two small pulmonary lobules (a, a), 

 with the air-cells (b, b), and the finest 

 bronchial twigs (c, c) ; upon which air- 

 cells are also placed. From a new-born 

 child. Half diagrammatic. Magnified 

 25 diameters. (Kolliker.) 



