CHAP, in] Prectitfni/ or Motor Ar< 21 



A considerable time having elapsed since the completion of the examination of these 

 anthropoid brains, I am now enabled to utter more mature considerations of the results obtained. 

 Further, the experience gained m the earlier work lias been made full use of in the more 

 important section of this investigation, namely, the application of these results to the human 

 brain and an attempt to determine the area which in man dominates the motor function. 



By way of introducing this subject I would here mention that the employment of similar 

 methods to those adopted in the anthropoid work, that is, the examination of carefully-prepared 

 serial sections of the cortex of the central convolutions, stained on the one hand for nerve 

 fibres and on the other for nerve cells, demonstrates the fact that in the human being a 

 histological area can be defined which corresponds remarkably closely with that existent in the 

 anthropoid cerebrum. 



Convinced of the importance of the giant cells of Betz ganglionic cells of Bevan Lewis 

 as determinants in the histological definition of the motor area, I have, in addition to the material 

 mentioned in the previous section, made a careful study of these elements in several other 

 normal brains. Then, in further confirmation of the accuracy of the results derived from a study 

 of tin- normal cortex, I have resorted to pathological material, and in this connection I shall have 

 some interesting remarks to make, first, on the changes found in the cortex cerebri of two 

 cases of Amyotrophic Lateral Sclerosis ; and, secondly, on the reactive alterations occurring in 

 the cortex in consequence of amputation of one or other extremity, alterations which have been 

 studied in seven instances. 



POINTS ON THE ANATOMY OF THE FISSURE OF ROLANDO. 



Facts to be mentioned hereafter make it clear that the distribution of those elements, 

 on the integrity of which the motor function depends, is directly influenced by the position 

 and course of the fissure of Rolando ; in fact, this interdependence seems to be so mutual 

 that anatomical variants in the disposition of the Rolandic fissure are in all likelihood associated 

 with corresponding variations in the allocation of the motor area. This being so it becomes 

 necessary to refer to some structural peculiarities and anatomical variations which may influence 

 motor localisation. 



To begin with, it is reasonable to assume that the upper part of the motor area is liable 

 to variations in accordance with variations in the position of the upper end of the fissure, for 

 although, as Cunningham has pointed out, in 60 / of cases the fissure incises the upper border 

 of the hemisphere and appears on the inner surface, in about '20 o it only just reaches the 

 upper margin, and in other 20 / it falls short by an appreciable distance. 



Then as to the lower extremity, Cunningham tells us that in 19 / (a high proportion in 

 my opinion) of cases it forms a connection with the "inferior transverse furrow of the fissure 

 of Rolando," and through this with the fissure of Sylvius. But I do not think that connection 

 h.i^ the effect of depressing the motor area, for in such cases an annectant gyms marks the 

 union of the two fissures and acts as a lower boundary for the motor field, just as the inferior 

 transverse furrow usually lies immediately below the motor area. In those cases, however, in 

 which the fissures of Rolando and Sylvius do not join, the interval separating them is very 

 variable, and the coincident shortening or lengthening of the Rolandic fissure may affect the 

 disposition of the motor elements. 



