218 Considerations on Function [CHAP. 



comparing the cell lamination in the two parts, merely leave the giant cells of Betz out 

 of consideration, and the differentiation of the two types becomes a matter of appreciable 

 difficulty. Similarly with the nerve fibres, the difference is only one of degree of fibre- 

 wealth, the plan of arrangement is alike, and both contain constituents of the same nature: 

 indeed, so great is the likeness that in sections stained for nerve fibres, in which the 

 cells of Betz are not apparent and cannot be used as guides, it is impossible to say with 

 absolute accuracy where one type terminates and the other begins. I repeat, therefore, that 

 these histological resemblances suggest a physiological relation, and knowing beforehand 

 what intimate connections exist between the Betz cell area and the system of lower motor 

 neurones, it is impossible for the histologist to believe that the " intermediate " area with 

 its kindred structure does not take a share of some kind in the conduct of motor 

 performances. 



Let us think next of what experiment teaches concerning this area. Let us recall for 

 a moment the extent of the field found susceptible to electrical excitation by observers who 

 experimented prior to Sherrington and Grtinbaum and who gave us our original maps of 

 motor localisation, and let us compare those maps with the scheme which I have drawn up 

 on a histological basis. In particular let the comparison be applied to the brain of the 

 anthropoid ape, and for this purpose the investigation conducted on the brain of the orang 

 (Simia Satyrus) by Beevor and Horsley may be specially chosen, because this is an animal 

 of which I have made collateral histological use. It is the anterior border of their area which 

 interests us most ; along the upper part of this, excitation produced movements of the neck, 

 along the lower part, movements of the eyes; and on looking at its position in Horsley 

 and Beevor's figures I think it will be agreed that it coincides, perhaps not precisely, but 

 remarkably closely, with my line of histological demarcation : indeed, excepting the part behind 

 the Rolandic fissure 1 , their whole area is practically identical with my combined " precentral " 

 and " intermediate precentral " fields. So much for the orang ; on broader lines the comparison 

 is capable of extension to the lower apes, but not having examined the brains of one of 

 these animals I am of course unable to say whether the agreement is equally close. Never- 

 theless, I think the assertion justifiable that just as the effects of unipolar faradisation as 

 employed by Sherrington and Grtinbaum are limited to the field of cortex distinguished by 

 what I have called the " precentral " type, so also the effects of faradic excitation as employed 

 by earlier experimenters do not extend beyond the limits of the field of cortex possessing 

 what I have called an " intermediate precentral " type of structure. In other words, coupled 

 with the structural differences which I have described, there are in the two precentral fields, 

 differences in reaction to faradism by which their extent can also be determined. Now it 

 seems idle to suppose that the invariable reaction to strong faradism of the anterior part 

 of this field and the remarkable agreement between its physiological and histological extent 

 means nothing: on the contrary it suggests in no weak manner that this cortex possesses 

 some motor property, and so an opening is made for further argument. 



It is interesting in the next place to compare my " intermediate precentral " area with 

 Flechsig's topographic schemes drawn up on the basis of myelogenic development. This 

 comparison affects the human brain. In Tafel IV of " Gehirn und Seele " (1890) repre- 



1 In the chapter on the " postcentral" area sufficient grounds have been given for believing that the postcentral 

 cortex is non-motor, and bearing on the point, it is interesting to find Beevor and Horsley stating that it was 

 much more difficult to excite movements from the postcentral than from the precentral cortex. 



