192 ORGANS OF DIGESTION. 



cation. After it has been masticated, and mingled with saliva, 

 it is moved backwards by the tongue, and passes down through 

 the esophagus into the stomach ; this act is called deglutition, 

 or swallowing. 



346. The wisdom and skill of the Creator is strikingly 

 illustrated in the means afforded to every creature for securing 

 its appointed food. Some animals have no ability to move 

 from place to place, but are fixed to the soil, as the oyster, 

 the polype, &c. ; these are dependent for subsistence upon such 

 food as may stray or float near them, and they have the 

 means of securing it only when it comes within their reach. 

 The oyster closes its shell, and thus entraps its prey ; the polype 

 has flexible tentacula (figs. 170 and 175), capable of great ex- 

 tension, which it throws instantly around any minute animal 

 coming in contact with them ; the cuttle-fish has elongated arms 

 about the mouth, furnished with ranges of suckers, by which 

 it secures its victim. 



347. Some are provided with instruments for extracting 

 food from places which would be otherwise inaccessible. Some 

 of the mollusca, with their rasp-like tongue (fig. ] 93;, perforate 

 the shells of other animals, and thus reach and extract the in- 

 habitant. Insects have various piercers, suckers, or a protrac- 

 tile tongue for the same purpose (figs. 195 to 199). Many of 

 the annelida, the leeches for example (fig. 178), have a sucker, 

 which enables them to produce a vacuum, and thereby draw 

 out blood from the perforations they make in other animals. 

 Many infusoria and rotifera are provided with hairs, or cilia, 

 around the mouth (figs. 171, 172), which, by their incessant 

 motion, produce currents that bring within reach the still more 

 minute creatures, or particles, on which they feed. 



348. Among the vertebrata, the herbivora generally em- 

 ploy their lips or their tongue, or both together, for seizing the 

 grass or leaves they feed upon. The carnivora use their jaws, 

 teeth, and especially their claws, which are long, sharp, and 

 moveable, and admirably adapted for the purpose. The wood- 

 peckers have long, bony tongues, barbed at the tip, with which 

 they draw out insects from deep holes and crevices in the bark 

 of trees ; some reptiles also use their tongue to take their prey ; 

 thus, the chameleon obtains flies at a distance of three or four 

 inches, by darting out its tongue, the enlarged end of which is 

 covered with a glutinous substance, to which they adhere. The 

 elephant, whose tusk and short neck prevent him from bringing 



