TEXT-BOOK OF PHYSIOLOGY. 



increased activity by the inhalation of irritating gases and into a tetanus by 

 pathologic causes as seen in the various forms of asthma. 



When the bronchial tube has been reduced to the diameter of about one 



Bronchiole.. 



Infundibulum 



FIG. 180. SCHEME OF A BRONCHIOLE TER- 

 MINATING IN ALVEOLAR PASSAGES, THOSE LEADING 

 INTO INFUNDIBULA BESET WITH AIR-CELLS. 

 (Landois and Stirling.) 



FIG. 181. SINGLE LOB- 

 ULE OF HUMAN LUNG. a. 

 Alveolar passage, b. Cav- 

 ity of lobule or infundib- 

 uium. c. Pulmonary sacs. 

 (Dalton.) 



millimeter, it is known as a bronchiole or a terminal bronchus. From the 

 sides of the terminal bronchus and from its final termination there is given 

 off a series of short branches which soon expand to form lobules or alveoli 



(Fig. 1 80). The cavity of the 

 alveolus is termed the infundib- 

 ulum. From the inner sur- 

 face of the alveolus and of the 

 passageway leading into it, there 

 project thin partitions which 

 subdivide the outer portion of 

 the general cavity or infundib- 

 ulum into small spaces, the so- 

 called air-sacs or air-cells (Fig. 

 181). The wall of the alveolus 

 is extremely thin and consists of 

 nbro-elastic tissue, supporting a 

 very elaborate capillary network 

 FIG. 182. SECTION OF SILVERED LUNG OF KITTEN, o f blood- vessels. The bron- 

 INCLUDING PORTIONS OF INFUNDIBULUM AND AIR- , . i 

 SAC. a. Small polyhedral epithelial cells covering phial System as far as the alveo- 



the wall of the infundibuium. b. Fibre-elastic lar passages is lined by ciliated 



framework, c. Large flattened epithelial plates lining epithelium. The air-SaCS are 

 air-sac, among which lie small groups of small cells .. r . , 



(d). (Pier sol* lined by flat epithelial plates of 



irregular shape, termed the res- 

 piratory epithelium (Fig. 182). The alveoli are united one to another by 

 nbro-elastic tissue. 



The bronchial arteries which supply nutritive material to the pulmonary 



