240 



THE EESPIRATOEY SYSTEM 



adjacent pulmonary alveoli. The terminal portion of each bron- 

 chiole enters the apex of a pulmonary lobule and divides into sev- 

 eral so-called terminal bronchioles (" respiratory bronchioles " of 

 Kolliker). 



FIG. 202. FROM A SECTION OF A CHILD'S LUNG. 



. bronchiole in transaction, with its adjacent pulmonary artery, A ; TB, bronchiole, 

 ending in a terminal bronchiole, from which are derived the infundibulum, /, the 

 atrium, A, and the pulmonary alveoli, PA. In the center of the figure a pulmonary 

 alveolus, PA, is seen in transection; many similar ones are shown. Hematein and 

 eosin. Photo, x 45. 



The terminal bronchiole is lined by flattened non-ciliated epi- 

 thelium which rests upon a thin fibro-muscular coat, the continua- 

 tion of the mucous membrane of the bronchioles. The muscle still 

 forms an almost complete though very thin investment of circular 

 fibres ; the muscle fibres, however, are not continued into the wall 



