The Air 'Bladder 139 



have to cross over (see Figure 18), and sometimes the food 

 gets into the passage leading to the lungs. It "goes down 

 the wrong way." 



And so, when you choke over a piece of bread, it may, or 

 it may not, be some consolation to you to realize that that 

 particular bit of discomfort had its origin in the Devonian 

 drought some three hundred million years ago. 



