THE CENTRAL NERVOUS SYSTEM 865 



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 per- 

 fectly capable of rational speech. He may talk to himself or on a 

 set topic with fluency and sense, may write intelligently, and under- 

 stand 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. While it was still believed that the cortex was 

 inexcitable, epilepsy was supposed to be exclusively due to morbid 

 conditions, structural or functional, of the medulla oblongata 

 (Kussmaul and Tenner). Some more recent writers have put 

 forward precisely the opposite opinion, that the disease is always 

 cortical in origin (Unverricht, etc.). What we know for certain is 

 that some cases of epilepsy, but only a minority, are associated 

 with cortical lesions. Among these are the cases of so-called Jack- 

 sonian 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 Jack- 

 sonian may spread so as to involve the whole body, in \vhich case 

 the symptoms become identical with those of ordinary epilepsy, 

 including the loss of consciousness. It has been found possible in 

 some cases to localize the position of the lesion from the part of the 

 body in which the fit, or the aura (the sensation or group of sensations 

 peculiar to each case, which precedes and announces the attack) begins. 

 For example, if the convulsions commence with a twitching of the 

 right thumb and extend over the arm, or if the aura consists of sen- 

 sations beginning in the thumb, there is a strong presumption that 

 the seat of the lesion is the part of the arm-area known as the 

 ' thumb-centre ' in the left cerebral hemisphere. It is the seat of 

 the convulsion at its commencement, not the regions to which it may 

 afterwards spread, that is important in diagnosing the position of 

 the lesion. For just as strong or long-continued electrical stimula- 

 tion of a given ' centre ' of the ' motor ' cortex may give rise to con- 

 tractions of muscles associated with other ' centres,' so the excitation 

 set up by localized disease may spread far and wide from its original 

 focus, involving area after area of the ' motor ' region first in the 

 one hemisphere and then in the other. The part of the body to 

 which a sensory aura is referred is as significant an indication of the 

 seat of the discharging lesion as is the part of the body which first 

 begins to twitch. This is one of the proofs that the ' motor ' region 

 is not a purely motor area. 



Seat of Intellectual Processes. When we have deducted 

 from the cortex of the hemisphere the whole Rolandic region 

 and the sensory centres, there still remains a large territory un- 

 accounted for. Considerable portions of the occipital, parietal, 

 and temporal lobes, nearly the whole of the island of Reil and 

 the greater part of the frontal lobe anterior to the ascending 

 frontal convolution are ' silent areas/ and respond to stimulation 

 by neither motor nor sensory sign. They correspond to the 

 association centres previously referred to. By a process of 



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