6o6 THE POPULAR SCIENCE MONTHLY.. 







that binds together the different jiarts of the cerebro-spinal system and 

 which makes it probable that a simple local trouble will produce gen- 

 eral functional perturbation. The brain is like a complex machine, in 

 which, if a screw loosens, or a nut gives way, or a rod bends or breaks, 

 at once all goes wrong. It is not that the screw, nut, or rod in question 

 is the immediate cause of the movements of the machine, but that 

 the failure of these accessories may, for the moment, produce accidents 

 as grave as would be caused by disturbance in much more important 

 parts. Again, cerebral lesions tend to spread and become general. 

 And yet, we have to accept the lesions caused by disease, for we can 

 not produce them at will. 



With these reservations, the clinical method is still of the first im- 

 portance. By means of it we verify in man the hypotheses of experi- 

 ment, and assure ourselves of the existence of the intellectual and 

 sensitive regions of the brain. Neither medicine nor physiology op- 

 poses the use of the clinical method in cerebral localization. But only 

 circumscribed lesions that have little or no tendency to become gen- 

 eral, or to act at a distance by compressing the brain, or otherwise, can 

 come to the aid of our theory. When there is a lesion of the cortical 

 region of the brain which fulfills these conditions, the resulting symp- 

 toms may be of two orders either stimulative or paralytic of the true 

 function. These are the two opposed symptoms that we produce ex- 

 perimentally by electrization and ablation of the substance of the con- 

 volutions. It goes wdthout saying that the symptoms vary with the 

 locality of the lesion : the intellectual region gives delirium ; the motor 

 region, spasms ; the sensitive region, subjective sensations. The symp- 

 toms of functional paralysis are also diversely represented by mental 

 feebleness, motor paralysis, and anaesthesia limited to one sense. A 

 lesion frequently presents both orders of symptoms, which succeed 

 each other, or alternate, according to its nature. This fact is as im- 

 portant as the division of the symptoms into two great classes. We 

 will now consider the facts in the same order as before. 



The middle region of the superior face of the brain appears to 

 be the motor region. In fact, limited lesions of this region bring 

 on marked troubles in the motor innervation of the body, such as 

 monoplegia, or limited paralysis, or equally limited spasms. Putting 

 aside those cases where the lesions cause general trouble, and regard- 

 ing those where the symptoms are limited, we come at a constant 

 relation between certain lesions and certain troubles. In ocular 

 monoplegia, the eye can not be controlled by the will. Brachial and 

 crural monoplegia are more frequent ; sometimes a single member, 

 arm or leg, sometimes both ; but successively, because of the extension 

 of the lesion to both centers, which are near together. In this case the 

 lesion advances slowly and invasively ; at the autopsy we can often 

 appreciate the differences of age of the extreme points of the diseased 

 spot. Not far from the brachial and crural centers is the center that 



