258 Mr. Victor Horsley [March 27, 



puscles and fibres provided, and that where numerous ideas have to 

 be functionalised, there numerous small corpuscles are arranged for 

 the purpose. 



But now the special interest attaching to the sensory perceptive 

 areas is that they, unlike the motor areas, tend to be related to both 

 sides of the body. With our habit of constantly focussing the two 

 eyes on one object, it will strike you at once that habitually we can 

 only be attentively conscious of one object at a time, since both eyes 

 are engaged in looking at it, and as you know we cannot as a matter 

 of fact look at two things at once. 



Hence I take it, both sensory perceptive centres are always fully 

 occupied with the same object at the same moment, and that therefore 

 we have complete bilateral representation of both sides of the body in 

 each hemisphere. As a further consequence, each sensory perceptive 

 area will register the idea that engaged it; in other words, both 

 centres will remember the same thing. Thus it happens that each 

 sensory area can perform the duty of the other, and therefore it is a 

 matter of comparative indiflference whether one is destroyed or not, 

 and as a matter of fact when this happens we find that the person or 

 animal recognises objects as they actually are, and in fact has no 

 doubt as to their nature. Here you see anatomically the reason of 

 this peculiarity is found to be that the optic or seeing nerves cross 

 one another incompletely in going to each hemisphere, and thus 

 each sensory centre represents half of each eyeball. 



I must pass rapidly to the description of the rest of the surface of 

 the brain — the hinder and front ends. At the outset I must admit 

 that all our knowledge concerning them is very hypothetical in the 

 absence of positive experimental results. 



This much we can say, that they are probably the seats of in- 

 tellectual thought, for many reasons which I have not time to detail. 

 Further we know that these intellectual areas are dependent for their 

 activity entirely on the sensory perceptive centres, for the dictum 

 that there is no consciousness in the absence of sensory stimulation is 

 very well established, as I shall now show you, however astounding 

 it may appear. In the first place, you will remember that when we 

 wish to encourage that natural loss of consciousness which we call 

 sleep, we do all we can to deprive our sense organs and areas of 

 stimulation ; thus we keep ourselves at a constant temperature, we 

 shut off the light, and abolish all noises if we can. But a most 

 valuable observation was made a few years ago by Dr. Striitnpell, of 

 Leipzig, who had under his care a youth, the subject of a disease of 

 the brain, &c., which while destroying the function of one eye and 

 ear, besides the sensibility to touch over the whole body, still left 

 him when awake quite conscious and able to understand, &c., using 

 his remaining eye and ear for social intercourse. Now when these 

 were carefully closed he became unconscious immediately, in fact 

 slept, and slept until he was aroused again, or woke naturally as wc 

 nay after some hours. 



