60 Precentral or Motor Area [CHAP. 



come across scattered nests of large pyramidal cells, which differ from those common to the 

 whole precentral cortex in being more attenuated and in having longer processes and larger and 

 more distinct chromophilic elements, and although these cells have to be very carefully sought 

 for, and it is correspondingly difficult to define their exact location, I yet think it possible 

 that they represent the cortical origin of the fibres contained in the cerebral root of the 

 fifth nerve (mastication), and also of the fibres proceeding to the nucleus of the seventh nerve. 



ON THE EVIDENCE DERIVED FROM A CLINICAL STUDY OF LESIONS OF THE 

 MOTOR AREA IN THE HUMAN BEING. 



Putting together the results of Professors Sherrington and Griinbaum's elaborate experiments 

 on the anthropoid ape, the facts brought to light by a full histological examination of the 

 Rolandic cortex in the normal subject, and the evidence derived from a study of the same 

 part in cases of Amyotrophic Lateral Sclerosis and Amputation, the case for the direct con- 

 nection between the pre-Bolandic cortex and the motor function appears practically complete. 



And yet, when we take up clinical records for further evidence on the question of the 

 limitation of this function, we at once receive a check by being confronted with this serious 

 difficulty, namely, that, from the very beginning observers have been firmly imbued with the 

 belief that the entire Rolandic region, so called, is " motor," and the obvious result is that 

 the baneful influence of this preconceived notion has made itself felt throughout the whole 

 of the very extensive literature on the subject. This being so, it is profitless to analyse 

 recorded cases for confirmatory evidence on the point under consideration, for, although no 

 doubt many cases could be adduced in support of the new localisation, many others would 

 appear to favour the old, and the result would be inextricable confusion. 



But apart from the assumption that experimenters gave the clinician what we now belir\r 

 to be a false lead, there are other factors which may have contributed to erroneous conceptions 

 on the function of the two central convolutions. Firstly, the simple anatomical truth is not 

 sufficiently recognised that the bases of the medullary projections of these two gyri are 

 separated from one another at most by the mere width of cortex on the apposed walls of 

 the Rolandic fissure, and that consequently the efferent and afferent fibres which proceed to 

 and from these gyri strike the centrum ovale side by side, and of course preserve this contiguity 

 in the path which they follow to the internal capsule. Bearing this in mind, to those familiar 

 with the morbid anatomy of the brain it is plain, that a lesion which would destroy the 

 whole or even a portion of one of these convolutions, without injuring fibres pertaining to 

 the opposite side, would be an anatomical rarity, and accordingly, whether the lesion be in the 

 postcentral or precentral gyrus, the resulting phenomena as regards paralysis would be the 

 same. And as a matter of fact when we consider the lesions from which clinical deductions 

 have been drawn, we find that they practically all come under the heading of cerebral softening, 

 tumour, haemorrhage, meningitis, or traumatism, and of these, softening following embolism or 

 thrombosis has been the agent in by far the majority of instances. As to cerebral softening, 

 it can hardly be maintained that an arterial occlusion is the most desirable agent for the 

 production of a lesion, which will give us the minimum of destruction with a maximum effect 

 so far as motor symptoms are concerned ; for from my own experience of over two hundred 

 examples of this condition, occurring in various parts of the brain, I can safely say that an 

 occlusion giving rise to destruction of the cortex alone without involving the white substance 

 is extremely uncommon ; further, in the instances which I have seen of stoppage of those 



