246 THE STORY-BOOK OF SCIENCE 



uncle's face that spoke from the depth of his heart. 

 After a moment's pause Uncle Paul continued: 



4 'There is, however, a need before which hunger 

 and thirst, however violent they may be, are mute; 

 a need always springing up afresh and never satis- 

 fied, which continually makes itself felt, awake or 

 asleep, night or day, every hour, every moment. 

 It is the need of air. Air is so necessary to life 

 that it has not been given us to regulate its use, as 

 we do with eating and drinking, so as to guard us 

 from the fatal consequences that the slightest for- 

 getfulness would cause. It is, as it were, without 

 consciousness or volition on our part that the air 

 enters our body to perform its wonderful part. We 

 live on air more than anything else; ordinary nour- 

 ishment comes second. The need of food is only 

 felt at rather long intervals; the need of air is felt 

 without ceasing, always imperious, always inexor- 

 able." 



"And yet, Uncle," said Jules, "I have never 

 thought of feeding myself with air. It is the first 

 time I ever heard that air is so necessary for us." 



"You have not given it a thought, because all that 

 is done for you; but try a moment to prevent air 

 entering into your body: close the ways to it, the 

 nose and mouth, and you will see!" 



Jules did as his uncle told him, shut his mouth 

 and pinched his nose with his fingers. At the end 

 of a moment, his face red and puffed up, the little 

 boy was obliged to put an end to his experiment. 



"It is impossible to keep it up, Uncle; it suffo- 



