50 The Encephalon 



Were the hemiplegia to be on the same side as the cerebral lesion, 

 the explanation would be that, from an error of development, there 

 was no crossing in the pyramids, but that all the motor fibres had 

 descended uncrossed, like the fibres in the column of Tiirck (p. 215). 

 This element in the calculation, however, may practically be dis- 

 regarded. 



In irritation of the motor area, as from meningitis or slight haemor- 

 rhage, there is twitching of the muscles of the opposite side, but when 

 the area is destroyed, as by abscess, injury, softening, or tumour, there 

 is complete paralysis of motion only on the opposite side, with sub- 

 sequent contracture of the muscles. The larger the area affected, the 

 more extensive the hemiplegia. Thus, in the case of softening in the 

 neighbourhood of the left fissure of Rolando, there will be right hemi- 

 plegia, right fac'iRl paralysis, and also aphasia. The softening is 

 usually caused by plugging of the middle cerebral artery, and, the area 

 of brain being suddenly deprived of its supply, the symptoms are much 

 like those of apoplexy. 



Disease in the motor area, as already remarked, causes loss of 

 voluntary movements in the muscles of the opposite side ; and, as the 

 lateral columns of the cord become involved in a descending degenera- 

 tion (p. 222), spasm and subsequent rigidity of these muscles are 

 entailed. The degeneration may be traced by the microscope through 

 the crus cerebri, anterior pyramid, and the antero-lateral column of 

 the cord. There is no loss of sensation in these cases, unless, indeed, 

 the degeneration extends deeply into the hemisphere. When haemor- 

 rhage has occurred, and is continuing from a middle cerebral artery, 

 the patient should be propped up in bed, so as to retard somewhat 

 the leakage ; and it is a question whether in some of these cases con- 

 tinuous compression, or even ligation, of the common carotid might 

 not be resorted to with advantage. 



Varieties of paralysis. Paralysis of the arm with the leg consti- 

 tutes bracJiio-crural monoplegia ; the condition is a common one, for a 

 tumour implicating the upper part of the arm-centre need spread but 

 little to interfere with that of the leg. Perhaps the arm-centre might 

 first be attacked, and then, as the growth extended upwards, leg-para- 

 lysis would follow, and as it extended downwards facial paralysis and 

 aphasia would result. 



The exact sitttation of the leg-centre is probably in the superior 

 parietal lobule and in the para-central lobule (p. 53). Thus, briefly, 

 the leg-centre is about the top of the fissure of Rolando. 



Crural monoplegia means paralysis of the muscles of the lower 

 extremity only (ftovos, alone} that is, without any implication of the 

 muscles of the upper extremity. 



Brachial. The centres for the arm, hand, %n&fingers are extensive, 

 just as the movements of the limb are important and complicated ; 

 they are situated about the middle of the ascending frontal and ascend- 



