PARTS OF ANIMALS, II. xvii. 



XVII. Under the vaulted roof of the mouth is Tongu©. 

 placed the tongue, and it is practically the same in 

 all land-animals ; but there are variations in the other 

 groups, whose tongues are as a whole different from 

 those of land-animals and also different among them- 

 selves. The human tongue is the freest, the broadest, 

 and the softest of all : this is to enable it to fulfil 

 both its functions. On the one hand, it has to per- 

 ceive all the various tastes, for man has the most 

 delicate senses of all the animals, and a soft tongue 

 is the most sensitive, because it is the most re- 

 sponsive to touch, and taste is a sort of touch. It 

 has, also, to articulate the various sounds and to 

 produce speech, and for this a tongue which is soft 

 and broad is admirably suited, because it can roll 

 back and dart forward in all directions ; and herein 

 too its freedom and looseness assists it. This is 

 shown by the case of those whose tongues are slightly 

 tied : their speech is indistinct and lisping, which 

 is due to the fact that they cannot produce all the 

 sounds. 



A tongue which is broad can also become narrow, 

 on the principle that the great includes the small, 

 but not vice versa. That is why the clearest 

 talkers, even among birds, are those which have ^ 

 the broadest tongues. On the other hand, the 

 blooded viviparous quadrupeds have a limited vocal 

 articulation ; it is because their tongues are hard 

 and thick and not sufficiently loose. Some birds — 

 the smaller sorts — have a large variety of notes. 

 The crook-taloned birds have fairly broad tongues. 

 All birds use their tongues as a means of communica- 

 tion with other birds, and some to a very consider- 

 able extent, so much so that it is probable that in 



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