KESPIKATION. 



iu'. 10. 



Following out the bronchial tubes from the diameter of 



o 



- ff \ of an inch, the smallest, which are from -&> to ,V f an 

 inch in diameter, open into a collection of oblong vesicles, 



which are the air- 

 cells. Each collec- 

 tion of vesicles con- 

 stitutes one of the 

 true pulmonary lo- 

 bules, and is from 



TO to TIT f an i nc h 

 in diameter. After 



entering the lobule, 

 the tube forms a sort 

 of tortuous central 

 canal, sending oif 

 branches which ter- 

 minate in groups of 

 from eight to fifteen 

 pulmonary cells. 

 The cells are a little 

 deeper than they are 

 wide, and have a 

 rounded blind ex- 

 tremity. Some are 

 smooth, but many 

 are marked by little 

 circular constrictions, or rugae. In the healthy lung of the 

 adult, after death, they measure from -g-J-g- to ^ or -^ of an 

 inch in diameter, but are capable of very great distention. 

 The smallest cells are in the deep portions of the lungs, and 

 the largest are situated near the surface. By sections of lung 

 inflated and dried, Magendie demonstrated, a number of 

 years ago, that there is a considerable variation in the size 

 of the cells at different periods of life ; that the smallest 

 cells are found in young children, and that they 



of a terminal bronchus and a group cf air-cells 

 moderately distended by injection, from the human subject. 

 (After liobin.) 



