530 SCIENCE PROGRESS 



Now it is obvious that to achieve such feats the speech 

 mechanism of the tongue must be simple and unhampered 

 from an engineering standpoint. Let us examine briefly how 

 the genio-glossus muscle acts when we articulate certain sounds. 

 When we pronounce the letter T the tip of the tongue is 

 placed against the front part of the palate by the contraction 

 of the upper intrinsic fibres of the lingualis superior. In this 

 position the front fasciculi of the fan-like genio-glossus are 

 drawn taut, so that a simple shortening will instantaneously 

 draw the tip of the tongue down. In pronouncing the hard 

 G and K exactly the same thing takes place with the central 

 bundles, while in the uttering of all vowel sounds and of 

 others where the exact placing of the upper surface of the 

 tongue against or near the palate is required, some or other 

 of the bundles of fibres of the genio-glossus would be in a 

 position to exercise exact control with the greatest possible 

 mechanical advantage. 



Now all anatomists are agreed that the different parts of 

 the human genio-glossus muscle must act independently of one 

 another, because the posterior fibres appear to thrust the 

 tongue out while the anterior ones draw it in. The total 

 action is described in some books of anatomy as that of 

 lowering the central part of the tongue in the mouth as in 

 the action of sucking, and it has been suggested that this is 

 one of the important duties performed by the genio-glossus. 

 The writer, by a series of dissections of the muscles in young 

 animals and infants, soon became convinced that this view 

 could not be supported, since in early life the genio-glossus is 

 smaller in proportion to the rest of the tongue than it is 

 later. Moreover, the act of sucking is common to all the 

 mammalia, and certainly man is not commonly credited with 

 any unique gifts in this direction. 



When the genio-glossus muscle came out of a deep pit, as in 

 the monkeys, and was " cabined, cribbed, confined " between the 

 lower jaw of the under-surface of the tongue, it was impossible 

 for the separate fasciculi to exercise the free movements 

 requisite for articulate speech. Hence as soon as this new 

 function was demanded we find that nature discarded the pit 

 and designed another method of obtaining engine-room beneath 

 the tongue. 



This was effected by a tilting forwards of the lower surface 



