i VD PHYSIOLOGY, 273 



Fig, 268. 



Lungs of Serpents, a. Trachea. K Bronchi, c. Eight Lung, c f . Left Lung. 

 d. Pulmonary Artery. 



for example, the bronchi terminate in capacious cavities, upon 

 the sides of which are the pulmonary blood-vessels. In many- 

 serpents the pulmonary apparatus consists of a long cylindrical 

 sac or lung upon the right side of the body, the corresponding 

 one on the left side being merely rudimentary, as seen in Fig. 

 268. Serpents are capable of expiring and inhaling large 

 quantities of air, which compensates for the want of a great 

 internal surface of lungs. And the peculiar hiss made by 

 them is simply a prolonged expiration of air from the lungs. 



How is it in frogs and serpents? What makes the hiss of serpents ? 



