418 



KNOWLEDGE. 



November, 1913. 



more critical action of withdrawing it at the proper 

 moment is due to the front fibres of the genio-glossus, 

 which become taut and braced for instantaneous 

 action as soon as the tongue-tip is pressed against 

 the palate. 



In Figure 497 it is seen that in the hard G or K 

 exactly the same thing takes place with the central 

 fasciculi of the muscle. A like action comes in with 

 sounds involving L, N, R, D, J, Q ; while in S, X, 

 and all other consonants where the nice adjustment 

 of the distance of the tongue from the palate is a 

 matter of moment the genio-glossus muscle is 

 capable — and appears to be the only structure 

 capable — of exercising a quick and exact control. 

 The same applies to the vowels, as is well shown 

 in the accompanying diagrams after Von Meyer's 

 drawings. Von Meyer, however, has not shown 

 the genio-glossus muscle in action as it is shown 

 here, and indeed, strangely enough, does not give 

 it a word of mention as a factor in articulate speech. 



It is worth while to take note of the fact that 

 practically all the speech-movements of the tongue 

 take place in the neighbourhood of its central line, 

 and that the sides play a very subordinate part. 

 Hence the other extrinsic muscles, such as the hyo- 

 glossus and stylo-glossus can have little or no part 

 in articulation (see Figure 488). 



Now let us return to our inferior maxilla and 

 examine the attachments and relations of the genio- 

 glossus. It is obvious that for quick, precise move- 

 ments, such as those demanded by articulate speech, 

 it must be unhampered and have plenty of room to 

 act. An examination of the arrangements for the 

 play of the muscle in different animals is exceedingly 

 instructive. In the dog, and indeed the majority of 

 the mammalia, the tongue lies flat upon the lower 

 jawbone leaving practically no room for any muscular 

 machinery. If, however, a photograph of a plaster 

 cast of the inner surface of the wolf's jaw (see 

 Figure 471) is compared with that of the baboon (see 

 Figures 473 and 474), which outwardly resembles it, 

 a remarkable difference of shape is evident. 



In all the monkeys — and even lower down the 

 scale among the lemurs — we find that Nature has 

 made provision for working room for the 

 genio-glossus muscle by excavating a kind of 

 pit on the inner surface of the mandible beneath 

 the tongue. This pit has been noticed by 

 various comparative anatomists, but I had never 

 seen any explanation of the reason why it exists, nor 

 was I aware of its function, until a series of dissec- 

 tions of monkeys' jaws showed in every case the tiny 

 tendon of the genio-glossus coming from the lower 

 surface of the deepest part of the pit (see Figures 

 433 and 486). The more doglike the jaw is, as in the 

 baboons — the more, in fact, it corresponds in general 

 outline with the prevalent type of the mandible 

 among lower vertebrates- — the deeper is this pit. 

 As soon, however, as the mandible begins in some 

 degree to resemble our own, as in some chimpanzees 

 and gibbons, and the whole lower surface becomes 

 tilted forwards, the pit seems to be no longer needed, 



and becomes shallower. One may as well remark in 

 passing that it is of course obvious that originally 

 the genio-glossus muscle had nothing whatever to do 

 with articulate speech. The need it met in the 

 economy of lemurs and apes was probably that of 

 giving increased mobility to the tongue for sorting 

 food already in the mouth. This is plainly seen 

 when we give a monkey a nut and see him crack it 

 and turn it about with his tongue, selecting the 

 kernel and rejecting every fragment of shell. This 

 ability common among all the Primates to sort food 

 with the tongue, and with its aid to eschew unac- 

 ceptable morsels, is strikingly absent in the case of 

 most animals. Anyone can assure himself of 

 this on seeing a dog try to get rid of some small 

 unpalatable object. Animals such as cattle, and 

 especially camels and giraffes, which are liable to get 

 dangerous thorns into their mouths, depend upon a 

 most elaborate arrangement of the long papillae 

 lining their cheeks, so that by a simple backward 

 and forward movement of the tongue such things 

 are at length extruded. 



There seems little doubt but that it is this sorting 

 machinery of the tongue in the lower Primates which 

 has been seized upon and greatly elaborated for the 

 new and wondrous mechanism of articulate speech. 



Before going further it may be as well to clear up 

 another point which seems to have puzzled some of 

 my audience when I was lecturing at Birmingham. 

 The question was asked me, " How is a parrot able to 

 talk if he has no chin ? " An equally pertinent 

 question would be, " How is a phonograph able to 

 talk when it possesses no chin ? " A parrot has 

 deep down behind its breastbone a marvellously 

 elaborate and versatile sound-producing apparatus, 

 almost as different from any possessed by ourselves 

 as is the mechanism of a phonograph. When man 

 began to speak, he had to make use of raw material, 

 which was there already, to build up his talking 

 machinery. That the parrot and the phonograph 

 can speak, merely proves that there are other ways of 

 doing it ; but the only question which we here have 

 to discuss is how man did it himself with such 

 means as were at his disposal. 



When we come to examine the difference between 

 prehistoric man and modern savages we find the 

 same order of structural change in the mandible still 

 going on, tending to the greater efficiency of the 

 genio-glossus muscle for speaking purposes. When 

 this fanlike group of muscular fibres came out of a 

 deep pit, such as is seen in the illustration of the 

 jaws of the lower monkeys, the fibres were obviously 

 hampered by being bunched and huddled together 

 (see Figure 486). As the jaw became tilted 

 forward, giving more engine room beneath the 

 tongue, the need for the pit became less, and it 

 becomes shallower and shallower until we find it a 

 mere depression, as in the Siamang gibbon (see 

 Figure 435). These changes are plainly shown 

 in the series of plaster casts of which photo- 

 graphs are reproduced in Figures 432 to 441. First 

 of all is a fossil lemur, in which the jaw still retains 



