454 PHYSIOLOGY 



rise in intellectual, i.e. associative, capacities, were it not for the invention 

 of SPEECH. 



In speech we have a symbolism which acts as an economy of thought or of 

 cerebral activities. An object, such as a table, with its associated properties 

 of colour, consistence, spatial extension, and resistance, with the connoted 

 acts associated with its use, can now be evoked as a word, involving com- 

 paratively simple auditory and motor processes, which itself may be em- 

 ployed as a unit of thought and brought into connection with other words, 

 each of which in the same way is the symbol for a whole series of sensory and 

 motor processes. The training of the cultivated man consists in a constant 

 extension of the range of this symbolism, and the acquisition of words 

 including wider and wider groups of neural processes, so that finally we arrive 

 at those short verbal collections which, as the so-called natural laws, sum- 

 marise the experience not only of the individual but such as is common to the 

 whole race of mankind. All science may in fact be regarded as an extension 

 of the process of representation of neural experience in symbolic shorthand, 

 which in the child begins with the utterance of such a simple word as 

 ' mamma,' and from which speech has arisen. A study of the nervous 

 mechanisms involved in speech is therefore of interest in its relations to the 

 development of the intelligence, and helps us to realise more completely the 

 conditions which determine the activity and functioning of the cerebral 

 hemispheres. Much light is thrown upon this mechanism by the study of 

 disorders in man grouped together under the name Aphasia. 



It has been usual to divide the disorders of speech known as aphasia into 

 various groups, as follows : 



(1) Motor aphasia, or aphasia of Broca. In this condition, which was de- 

 scribed fully by Broca and referred by him to a lesion of the third left frontal 

 convolution, the patient is unable to speak, although he understands what is 

 said to him and has been stated to suffer from no impairment of his intelligence. 



(2) Sensory aphasia, or aphasia of Wernicke. This condition was con- 

 nected by Wernicke with the existence of lesions in a fairly wide area, known 

 as the area of Wernicke, which involves the supramarginal and angular gyri 

 and the hinder portions of the first and second temporo-sphenoidal convo- 

 lutions. In these cases there may be limited power of speech, but there 

 is serious impairment of the intelligence and especially of the power of 

 appreciation of spoken words, so that the patient does not understand what 

 is said to him. This condition may or may not be attended with alexia, loss 

 of power to read. Any impairment of the motor processes of speech which 

 is present is due rather to the inability of the patient to appreciate 

 what he himself is saying, so that there is here a species of sensory paralysis 

 in the higher sphere of neural processes. 



(3) Anarthria. This is a condition in which there is marked impairment 

 of the motor powers of expression, although intelligence and appreciation 

 of speech, both spoken and written, may be unaltered. This condition is 

 generally associated with lesion of the white matter of the external capsule 

 as it passes round the lenticular nucleus, 



