972 THE CENTRAL NERVOUS SYSTEM 



A so-called temporary aphasia may occur without any structural 

 change in the speech-centre for example, during an attack of migraine. 

 In children it may even be caused by some comparatively slight irrita- 

 tion in the digestive tract, such as that due to the presence of a tape- 

 worm. 



In the anthropoid apes no evidence of the existence of any ' speech- 

 centre,' even distantly foreshadowing the human, has been obtained 

 by stimulating the inferior frontal convolution on either side. No move- 

 ments, and particularly no movements connected with vocalization, are 

 elicited. 



Sensory Aphasia. In typical motor aphasia spoken and written 

 words convey to the patient their ordinary meaning. They call up in 

 his mind the usual sequence of ideas, but the chain is broken at the 

 speech-centre, and the outgoing ideas cannot be clothed in words. The 

 expressive factor in speech is deranged. In sensory aphasia the percep- 

 tive factor in speech is deranged. In ordinary sensory aphasia (Wer- 

 nicke's, or cortical sensory aphasia) the patient cannot understand 

 spoken or written language, but, far from being unable to speak, he 

 often babbles incessantly. He may string together a series of words, 

 each correctly articulated, but having no meaning, or may utter a jargon 

 not composed of known words at all. Instead of the words which he 

 desires to use to express his meaning, he may use others having a 

 similar sound (paraphasia). Damage to two regions of the brain has 

 been found associated with this condition : (i) the middle part of the 

 first and second temporal convolutions, (2) inferior parietal convolu- 

 tions and the angular gyrus in the neighbourhood of the occipital visual 

 centre. When the temporal region is alone affected, it is the spoken 

 word that is missed, the written that is understood (word-deafness). 

 When, as occasionally happens, the lesion is confined to the occipital 

 region, spoken language is perfectly understood, written language not 

 at all (word-blindness). It is the left hemisphere wh'ch is affected in 

 right-handed persons, the right hemisphere in left-handed persons. 

 Sensory, like motor aphasia, may exist in any degree of completeness, 

 from absolute word-deafness or word-blindness, in which no spoken or 

 printed word calls up any mental image, to a condition not amounting 

 to much more than a marked absence of mind or unusual obtuseness. 

 Motor and sensory aphasia may be present together. In well-marked 

 cortical word-deafness speech is always interfered with to some extent. 

 In so-called pure word -deafness (subcortical sensory aphasia) the patient 

 may be perfectly capable of rational speech. He may talk to himself 

 or on a set topic with fluency and sense, may write intelligently, and 

 understand what he reads ; but he may be unable to understand a single 

 word spoken to him, or to repeat words when asked to do so. 



Cortical Epilepsy. Disturbed action of the motor centres may take 

 the form either of depression or of increased excitability. The former 

 will be associated with partial or complete paralysis of the movements 

 represented in the area, the latter by abnormally intense or prolonged 

 discharge leading to the condition called cortical epilepsy that is, 

 epileptic attacks associated with cortical lesions. Among these are the 

 cases of so-called Jacksonian epilepsy a condition characterized by the 

 fact that the seizure does not begin by general, but by local, convulsions. 

 They may remain confined to a single limb, or to one side of the face, or 

 to one side of the body. So long as the convulsions are not general, 

 consciousness need not be lost. Or a seizure beginning as Jacksonian 

 may spread so as to involve the whole body, in which case the symptoms 

 become identical with those of ordinary ep'Jepsy, including the loss of 

 consciousness. It has been found possible in some cases to localize the 



