1903.] Histological Studies on Cerebral Localisation. 489 



brain, but coinciding absolutely with the field which Sherrington and 

 Grunbaum have recently found responsive to unipolar faradization in 

 the same animals. 



Strong confirmatory evidence in support of the assumption that in 

 man, as well as in the man-like ape, the elements controlling volitional 

 muscular movements reside in this area, is afforded by an examination 

 of the brain in cases of Amyotrophic Lateral Sclerosis, a disease limited 

 in its attack to the motor system of neurones. In two such brains 

 submitted to exhaustive examination a wholesale disappearance of the 

 " giant cells " of Betz from the whole of their normal area of occupation 

 has been disclosed. In the same brains the post-central gyrus entirely 

 escaped affection. 



Valuable material for the determination of differential localization in 

 the motor field is afforded by the brains of individuals who have been 

 disabled by amputation of one or other extremity, for in due course, 

 either as a result of section of the nerve fibres with which they stand 

 connected, or of suppression of the energy which they elaborate, the 

 cortical "giant cells" controlling muscles in the amputated member, 

 undergo the change " reaction a distance " (Marinesco). In three cases of 

 amputation of the leg arid a like number of cases of amputation of the - 

 arm, in which the central convolutions were converted into serial 

 microscopic sections, alterations were discovered limited in distribution 

 to fields agreeing closely with Sherrington and Griinbaum's respective 

 leg and arm areas in the ape. 



The annectant gyrus or buttress at the level of the superior genu, 

 relatively barren in " giant cells," seems to be an important guide to 

 the point where the trunk area intervenes between those of the arm 

 and leg. 



IV. Post-central and Intermediate Post-central Areas. 



This area is readily defined in both man and the man-like ape, and 

 is limited in its distribution to the post-central or ascending parietal 

 gyrus and its paracentral annexe, the floor of the fissure of Eolando 

 forming a definite anterior boundary. 



Since its cortical structure differs markedly from that of the motor 

 area, and at the same time exhibits features common to known sensory 

 areas (the visual and auditory), its supposed motor function is denied, 

 and it is maintained on the following additional grounds that it con- 

 stitutes the terminus where fibres conveying common sensory 

 impressions primarily impinge. Physiologically it is silent under 

 the influence of electrical excitation, and also partial ablations give rise 

 to no interference with movement (Sherrington and Grunbaum). Its 

 fibres, like those of sensory spinal tracts, myelinate early (Flechsig and 

 Vogt) It is the terminus for the " cortical lemmscus (Tschermak). 



