CUTANEOUS AND SOME OTHER SENSATIONS. 705 



lobe corresponding to the motor region which is affected ; but there appears 

 to be no record of any case of a cortical lesion affecting sensation without 

 affecting movement. We have previously called attention to the fact that 

 the temporary loss or impairment of movement which follows removal of an 

 area is frequently, if not always, accompanied by an impairment of cutane- 

 ous sensations in the limb or part " paralyzed ;" and side by side with this 

 we may put the experience that in the human epileptiform attacks of cortical 

 origin, the seizure is at times ushered in by peculiar sensations, called the 

 " aura," in the part movements of which inaugurate the march of convul- 

 sive movements. But these things do not show that the cortical area is the 

 " seat of sensations ;" they rather illustrate what we said concerning the 

 complexity of the chain of which the events in the cortical area are links, 

 and the close tie between sensory factors and the characteristic elements of 

 the motor region. 



In the dog, while removal of almost any considerable portion of the 

 cortex affects sensation, removal of parts of the frontal region producing, 

 perhaps, less effect than removal of parts in other regions, the loss or im- 

 pairment of sensation appears to be transient, though having a duration 

 broadly proportionate to the extent of cortex removed ; and when a very 

 large portion of the cortex is removed, some imperfection appears to remain 

 to the end. We have already referred to the case of a dog from which the 

 greater part of both cerebral hemispheres had been removed, but which 

 remained capable of carrying out most of the ordinary bodily movements, 

 and that apparently in a voluntary manner ; in this case the " blunting " of 

 cutaneous sensations was perhaps more striking than the imperfection of 

 movement. It will be worth while to consider the condition of this dog a 

 little closely, on account of the light which it throws on the problem which 

 we are now discussing. 



Clinical experience shows that in man the integrity of the cerebral hemi- 

 spheres, and of the connection of the hemispheres with the rest of the central 

 nervous system, is essential to the full development of sensations ; and that 

 in this respect, each hemisphere is related to the crossed side of the body. A 

 very common form of paralysis or " stroke " is that due to a lesion of some 

 part of one hemisphere (the exact position of the lesion need not concern us 

 now), frequently caused by rupture of a bloodvessel, in which the patient 

 loses all power of voluntary movement and all sensations on the crossed side 

 of his body (including the face) ; he is said to be suffering from hemiplegia, 

 " one-sided stroke." Not only do voluntary impulses fail to reach the mus- 

 cles of the affected side, but sensory impulses, such as those which started, 

 for instance, in the skin, would, under normal conditions, lead to sensations 

 of touch, of heat or cold, or of pain, fail to affect consciousness, when they 

 originate on the affected side ; the patient cannot on that side feel a rough 

 surface, or a hot body, or the prick of a pin. For the sake of clearness we 

 suppose the loss of movement and sensation to be complete, but it might, of 

 course, be partial. Such a case shows, we repeat, that the integrity of the 

 cerebral hemisphere, and of the connection of that hemisphere, we may say 

 of the cortex of that hemisphere, with the other parts of the nervous system, 

 is essential to the development of the sensations ; but it does not prove that 

 the cortex of the hemisphere is the " seat " of the sensations, it does not prove 

 that the afferent and sensory impulses started in the skin undergo no mate- 

 rial change until they reach the cortex and are then suddenly converted 

 into sensations ; it only proves that in the complex chain of events by which 

 sensory impulses give rise to full conscious sensations the events in the cortex 

 furnish an indispensable link. And the phenomena of the dog in question, 

 on the one hand, illustrate how complex the chain is, and, on the other hand, 

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