PARTS OF ANIMALS, III. ni. 



anything coming in by mistake into the windpipe. If 

 there is any error in this movement, or if you breathe 

 in while you are taking food, coughing and choking 

 results, as I have said. But the movement of the 

 epiglottis and of the tongue has been so neatly 

 contrived that while the food is being masticated in 

 the mouth and is passing over the epiglottis, the 

 tongue seldom gets in the way of the teeth, and 

 hardly ever does any food slip into the windpipe. 



I mentioned some animals that have no epiglottis. 

 This is because their flesh is dry and their skin hard ; 

 and thus if they had one, it would not move easily, 

 because it would have to be made out of constituents 

 of this sort. It is quicker to contract the edges of the 

 windpipe itself than it would be to close an epiglottis, 

 if, as in the hairy creatures, it were made out of the 

 same sort of flesh as the rest of their bodies. 



This will suffice to show why some animals have an 

 epiglottis and some not ; how Nature has contrived 

 it so as 'to remedy the unsatisfactory position of 

 the windpipe in front of the oesophagus. Still, the 

 windpipe is bound by necessity to be in this position 

 for the following reason. The heart is situated in the 

 middle of the body and in the fore part of it ; and in 

 the heart, we hold, is the principle of life and of all 

 movement and sensation. Both of these activities 

 take place in the direction we call forwards : that is 

 the very principle which constitutes the distinction 

 between before and behind. The lung is situated in 

 the region of the heart, and surrounding it. Now 

 breathing takes place for the sake of the lung and 

 the principle which is situated in the heart : and the 

 breath passes through the windpipe. So, since the 



* τοΰτον SUY : τοΰτο vulg. 



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