ANIMAL NUTRITION. 



97 



may be called, as he strictly is, the omnivorous, or all-eat' 

 ing animal. 



ANIMAL NUTRITION. 



274. When we examine the structure of the very low- 

 est orders of animal existences, we find, that whatever 

 other parts may be wanting, whether they be eyes, or 

 ears, or nerves, or brain, or organs of locomotion, two 

 parts are always present, to wit, a mouth and stomach. 

 Without these, no animal can exist, for however com- 

 plex the organization in other respects may be, nothing 

 can compensate for the organs of nutrition. From the 

 account we have given of the structure of the hydra, 

 it would appear that nearly every other part usually con- 

 stituting an animal may be dispensed with, except these ; 

 and that some of the polypi consist of little or nothing 

 more than a throat and organs of digestion. 



275. Some animals have several Stomachs. Some of 

 the polypi tribes have at least four stomachs, and the aste- 

 ria or star-fish, a very common inhabitant of our sea- 

 shores, has ten distinct digestive organs. 



Fig. 71. 



276. The mouth of this animal, a, is situated in a de- 

 pression at the centre of the under surface, and leads into 

 a capacious sack or bag, placed immediately above it, 

 when the animal lies with the mouth downward, which 



What is said of the necessity of a mouth and stomach to each animal? 

 What is said of the number of stomachs possessed by some animals ? 



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