Internal Workings 141 



As a matter of fact, if fish tried to masticate their food as 

 good little children do, they would suffocate, for they would 

 then be unable to pass the current of water through their 

 mouths and over their gills which is necessary for their 

 breathing. To overcome this difficulty, some of the vege- 

 tarians, and others which like to chew, have grinding-mills 

 well down in their throats. These are called pharyngeal 

 teeth, and are supported by bony arches similar to those 

 which carry the gills. It is here that the "Fletcherizing," if 

 any, is done. 



Fish are largely carnivorous. Most of them, therefore, 

 have sharp-pointed teeth in the mouth with which to seize 

 their prey and hold it while it is being swallowed whole. 

 Those which feed on tiny living organisms in the water, like 

 the herring, have small delicate teeth. The rays live on 

 shell-fish, and have great flat teeth like paving stones with 

 which to crush the shells before swallowing them. Of the 

 few that go in for a vegetarian diet some, like the carp, have 

 no teeth in the mouth j while one of the strangest modifica- 

 tions is found in the "parrot." These large, brightly colored 

 fish graze on the coral reefs, and their front teeth have all 

 fused together to form a beak very much like a parrot's. 

 With this beak they nibble the coral and the weeds, which 

 are then ground up by the powerful pharyngeal teeth in 

 the throat. 



Many fish have an unlimited ability to replace their teeth, 

 not being confined to two sets as we are. This is particularly 

 evident in some of the sharks, whose mouths are bristling 

 arsenals of teeth, row after row, in diminishing size, lying 

 flat in readiness, waiting to take their turn in the front line 

 as the ones in active use wear out. 



As has been noted in an earlier section, the fish's tongue is 

 a flat, immovable projection from the floor of the mouth. 

 There is no salivary gland. 



