THE ORGANS OF RESPIRATION 



131 



a right and a left, which are termed the bronchi (Fig. 

 38, Br.). Each bronchus enters the lung of its own side, 

 and then breaks up into a great number of smaller 

 branches, which are called the bronchioles or bron- 

 chial tubes. As these diminish in size, the cartilages, 

 which are continued all through the bronchi and their 



Fig. 38. — Back View of the Neck akd Thorax of a Human Subject 



FROM WHICH THE VERTEBRAL COLUMN AND WHOLE POSTERIOR WaLL 



OF THE Chest are supposed to be removed. 



M. mouth ; Gl. glottis ; Tr. trachea ; L.L. left lung ; R.L. right lung; 

 £r. bronchus ; P. ^. pulmonary artery ; P. K. pulmonary veins ; ^o. aorta; 

 D. diaphragm ; H. heart ; V.C.I. vena cava inferior. 



large ramifications, become smaller and more scattered 

 and eventually disappear, so that the walls of the smallest 

 bronchial tubes are entirely muscular or membranous. 

 Thus while the trachea and bronchi ai-e kept permanently 

 open and pervious to au* by their cartilages, the smaller 



K 2 



