38 Precentral or Motor Area [CHAP. 



The estimated total number of giant cells in this hemisphere is 13,000. 



Finally, when the area containing giant cells is compared with that in which a motor 

 type of fibre arrangement obtains, we find that the latter overlaps the cell area to the extent 

 of about 2 mm., and so we have another repetition of the human arrangement. 



LOCALISATION EVIDENCE SUPPLIED BY AN EXAMINATION OF PATHOLOGICAL MATERIAL. 



A. The Central Cortex in Amyotrophic Lateral Sclerosis. 



In its clinical as well as its pathological manifestations, Amyotrophic Lateral Sclerosis 

 is essentially a disease of the muscular system and the motor system of neurones, and since 

 a preliminary examination of the muscles, peripheral nerves, spinal cord and medulla oblongata 

 in the two cases affording the material for this branch of my investigation revealed pro- 

 found alterations, it occurred to me that time spent in making an exhaustive examination 

 of the cortex of the central convolutions might be repaid by the discovery of changes in the 

 cortical neurones which would throw light on the question of motor localisation. In this 

 I have not been disappointed, and, in my opinion, the results I am about to relate constitute 

 the strongest confirmatory evidence yet adduced to support the assumption that, in man, as 

 well as in the anthropoid ape, the elements acting for the direct control of muscular movements 

 are confined to the precentral gyms and its paracentral annexe, and lie entirely in front of the 

 line of the fissure of Rolando. 



On the constancy of changes in the cortical neuronic elements in Amyotrophic Lateral 

 Sclerosis, there seems to be a division of opinion, for some who have examined the brain 

 in such cases have stated that it was free from change, while others have produced evidence to 

 the contrary. Of the positive evidence at our disposal, an observation recorded by Marinesco, of 

 Bucharest, is the first deserving of quotation. In his case the giant cells of the upper third 

 of the precentral gyms ("im oberen Drittel der vorderen Centralwindung ") had almost entirely 

 disappeared, only a few extremely atrophied members remaining. Collections of granular cells 

 could be seen occupying the position formerly held by some of the giant cells, and these 

 were presumed to be glial cells which had absorbed yellow pigment granules. The report 

 next credits him with a half-hearted and ambiguous statement to the effect that the Betz 

 cells in the postcentral gyri were more or less atrophied ("in den hinteren Centralwindungen 

 waren die Betz'chen Zellen mehr oder weniger atrophisch "). The latter statement I do not 

 consider worthy of serious consideration, and in reference to the limitation of the changes in 

 the precentral gyrus to the " upper third," I would mention that in giving accounts of alterations 

 in the giant cells in other conditions, Marinesco exhibits a noticeable tendency to limit the 

 affection to the same division, and he thereby gives one the impression that he denies the 

 existence of Betz cells at a lower level. 



Of other findings in the brain in such cases the following may be mentioned. In a 

 case of Mott's, admirably recorded on the pathological side, sections of the central convolutions 

 revealed absence of large pyramidal cells, but it is unfortunately not stated from what level 

 the sections were taken. In a more 'recent paper by the same writer in conjunction with 

 Tredgold, giving an account of five cases, the condition of the cortex is not specially gone into. 



