132 



ELEMENTARY PHYSIOLOGY 



bronchial tubes may be almost closed by the contraction 

 of their muscular walls. 



Fig. 39. 



A. Two infundibiila (h) with the viltimate bronchial tube (a) which 

 opens into them. (Magnified 'JO diameters.) 



B. Diagrammatic view of an air-cell of A seen in action ; a, epi- 

 thelium ; b, partition between two adjacent cells, in the thickness of 

 which the capillaries run ; c, fibres of elastic tissue. 



C. Portion of injected lung magnified : a, the capillaries spread over 

 the walls of two adjacent air-cells ; b, small branches of arteries and 

 veins. 



D. Poition still more highly magnified. 



Each 5ner bronchiole ends at length in an elongated dila- 

 tation about ^ of an inch in diameter on the average and 

 known as an infundibulum (Fig. 39, A. b). The wall 



