902 



THE LUNGS. 



The following writers, among others, maintain the existence of epithelium in the 

 air-cells: Addison, in Phil. Trans., 1842; Eossignol, Recherches sur la Structure 

 intime du Poumon, 1846; Waters, Anatomy of the Human Lung, 1860; Kolliker, in 

 his Gewebelehre; Eberth, in Virchow's Archiv. xxiv., p. 503 ; and Julius Arnold, in 

 Yirchow's Archiv. xxviii., p. 433 ; Hirschmann, in the same, xxxvi. with addition and 

 drawings by Chrzonszczewsky. The following are among those who deny the existence 

 of epithelium : Rainey, in Med.-Chir. Trans., vol. xxviii , 1845; and in Brit, and For. 

 Med.-Chir. Eeview, 1855; Radclyffe Hall, in Med.-Chir. Review, July, 1857; Luschka 

 and Henle, in their works on Human Anatomy; Badoky, in Virchow's Archiv., xxxiii. 

 p. 264. 



Fig. 631. 



Fig. 631. CAPILLARY NET- 

 WORK OP THE PULMONARY 

 BLOOD-VESSELS IN THE HU- 

 MAN LUNU (from Kolli- 

 ker). ^ 



The capillary network 

 of the pulmonary vessels 

 is spread beneath the thm 

 transparent mucous mem- 

 brane of both the ter- 

 minal and lateral air-cells, 

 and is found wherever the 

 finest air-tubes have lost 

 their cylindrical character, 

 and become beset with 

 cells. Around the ex- 

 terior of each cell there 

 is an arterial circle, which 

 communicates freely with 



similar neighbouring circles, the capillary systems of ten or twelve cells being 

 thus connected together, as may be seen upon the surface of the lung. From 



Fig. 632. Fig. 632. CAPILLARY NETWORK ON THE PUL- 



MONARY VESICLES OF THE HORSE (from Frey 

 after a preparation by Gerlach). '-f- 



a, the capillary network ; 6, the terminal 

 branches of the pulmonary artery passing 

 towards and surrounding in part each pul- 

 monary vesicle. 



these circular vessels, which vary in dia- 

 meter from i-^jifiToi to ^jgth of an inch, 

 the capillary network arises, covering the 

 bottom of each cell, ascending also between 

 the duplicature of mucous membrane in 

 the intercellular septa, and surrounding 

 the openings of the cells. As was pointed 

 out by Rainey, the capillary network, 

 where it rises into the intercellular parti- 

 tions, although it forms a double layer in the lungs of reptiles, is single in 

 the lungs of man and mammalia. 



The capillaries are very fine, the smallest measuring, in injected specimens, 

 from -* 11 to ** 1 of an ilicb ; tlie network is so close that the meshes 



