692 THE CEREBRUM 



to train animals to produce a definite number of associated sounds. 

 Instances of this kind are the "talking dog" and the "talking horse." 

 The higher monkeys, it is said, are capable of uttering a few coordinated 

 sounds in expression of particular mental concepts. 



A true coordination of sounds in the form of speech, however, 

 is shown only by man. This achievement is made possible very 

 largely by the development of the association area pertaining to 

 this function and not by a correspondingly much greater intricacy 

 of the motor apparatus necessary for speaking. Already dur- 

 ing infancy, man is equipped with a phonetic mechanism which is 

 practically complete as far as its structural complexity is concerned, 

 but is still in need of functional development. This it acquires 

 in the course of the succeeding years. This 

 awakening of the associations concerned in speech, 

 is one of the most interesting and instructive phe- 

 nomena in the life of man. The primary cooing 

 sounds of the infant are gradually amplified by a 

 number of successive sounds having a definite 

 meaning. This augmentation indicates an exten- 

 sion and melting together of intracerebral paths, 

 so that various impressions from other association 

 centers may be brought to bear upon speech. 

 Once this union has been effected, the develop- 

 ment of speech is much more rapid, being subject, 

 of course, to differences in the training of the child. 

 Speaking is the outcome of certain mental pro- 

 cesses; in other words, it is the result of particular 

 afferent impulses which may enter the body by 

 FIG. 347. THE SPEECH way o f p rac ti c ally any receptor. They are then 



CIRCUIT. j. i 



R Receptor- V as- associa ted in the perception and memory realms 

 sociation center; c/cen- of the corresponding regions of the cerebral cortex, 

 ter for speech; M, motor AS speech follows visual, auditory, tactile and other 

 larynx; L*\Jrynx. * impressions, it may be said that these mechanisms 

 are really tributary to the speech center. Hence, 

 speech is the product of a harmonious interaction between different 

 peripheral and central nervous mechanisms. It is true, however, that 

 these tributary complexes are not developed simultaneously but suc- 

 cessively, and that training has much to do with their functional 

 adaptability to speech. Thus, it is a common experience that the 

 memory sphere of vision becomes functional at an earlier date than 

 that of audition; at least, it seems more difficult for the infant to 

 make the latter subservient to its speech requirements. 



The morphological and functional arrangement of the adult 

 mechanism of speech may be illustrated best in the form of a diagram. 

 It has been said that speech is under the control of an association area 

 situated in the cortex of the cerebrum (Fig. 347). This center stands 

 in communication with the phonating organs, the larynx and allied 



