112 MINUTE STRUCTURE OF LUNG. 



hole in the side. Now, when the handles are separated, air 

 enters the nozzle, and when the handles are brought together 

 air is driven out. If a rubber balloon be tied to a glass tube 

 tightly corked in the nozzle of the bellows, and then the bel- 

 lows are Avorked, air will enter and innate the balloon when 

 the handles are separated, and air will rush out when the 

 handles are brought together. If the sides of the bellows 

 have a tight window, the changes in the balloon can be seen. 



To illustrate the minute anatomy of the lung, take a rubber 

 balloon, a glass tube, two rubber tubes, one dyed red, the other 

 blue, a bag of netting, with one side dyed red and the other 



....BRONCHIAL TUBE. 



VEIN I 



Fig. 44. Minute Structure of the Lungs, Showing Air Vesicles and 

 Capillaries. 



side blue. Tie the balloon 011 the end of the glass tube, slip 

 the bag of netting over the balloon, and tie it, with the ends of 

 the rubber tubes on the corresponding sides of the bag. Slip 

 a short piece of the rubber tube on the end of the glass tube, 

 and when the balloon is inflated shut the air in by means of a 

 pinchcock. The balloon represents an air vesicle, the glass 



