CHAPTER XI 



HOW ANIMALS EAT 



i 



i. The Prehension of Food. (i) Liquids. The sim- 

 plest method of taking nourishment, though not the 

 method of the simplest animals, is by absorption through 

 the skin. The tapeworm, for example, living in the 

 intestine of its host, has neither mouth nor stomach, 

 but absorbs the digested food with which its body is 

 bathed (Fig. 37). Many other animals, especially in- 

 sects, live upon liquid food, but obtain it by suction 

 through a special orifice or tube. Thus, we find a 

 mouth, or sucker, furnished with teeth for lancing the 

 skin of animals, as in the leech ; a bristlelike tube fitted 

 for piercing, as in the mosquito ; a sharp sucker armed 

 with barbs, to fix it securely during the act of sucking, 

 as in the louse ; and a long, flexible proboscis, as in the 

 butterfly (Fig. 221). Bees have a hairy, channeled 

 tongue (Fig. 220), and flies have one terminating in a 

 large, fleshy knob, with or without little " knives " at 

 the base for cutting the skin (Fig. 222); both lap, 

 rather than suck, their food. 



Most animals drink by suction, as the ox ; and a few 

 by lapping, as the dog ; the elephant pumps the water 

 up with its trunk, and then pours it into its throat ; and 

 birds (excepting doves) fill the beak, and then, raising 

 the head, allow the water to run down. 



Many aquatic animals, whose food consists of small 

 particles diffused through the water, have an apparatus 

 for creating currents, so as to bring such particles within 



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