204 



STUDIES IN ADVANCED PHYSIOLOGY. 



its scientific sense, but in the original sense it had, meaning 

 a little chamber. In this way one single alveolus may, by 



Fig. 88. CILIATED EPITHELIUM FROM THE TRACHEA OF A RABBIT. (After Schafer.) 

 w 1 , m 2 , m 3 , mucus-secreting cells lying between the ciliated cells. 



the folding of its walls, give rise to a great many air cells. 

 In the walls of these air cells run the pulmonary capillaries, 

 and at this point the gaseous interchange of the blood takes 



Fig. 89. DIAGRAMMATIC REPRESENTATION OF THE TERMINATION OF A F.ROXCHIAL TUBE 

 . IN A GROUP OF ALVEOLI. (After Schafer.) 



B, bronchial tube; L. , bronchiole; A, atrium; 1, Alveolus; c, c, individual air 

 cells. 



place. The anatomy of the bronchial tubes and their finer 

 divisions does not differ materially from that of the trachea. 

 The cartilaginous rings, however, become less regular and 



