m] Dt'tfifcfioiHi from (.'li'ii f ml Jteconh 01 



offshoots nt' the middle eeivbral artery which supply the lower two-thirds, or thereabouts, 

 of the central gyri, and of those terminal twigs of the anterior cerebral artery which run to 

 the pararetitral lobule and upper third of the central gyri, there have been none which have 

 not penetrated so deeply into the white substance as to affect fibres pertaining to both 

 gyri. Frequently, also, I have been struck with a point, to which Monakow draws attention, 

 na Iv. that in some cases, when the patch of cortical destruction has appeared small and in- 

 significant from the surface, more minute inspection, especially after hardening, has revealed 

 an unexpected widespread destruction of the subjacent white substance; and further I cannot 

 help agreeing with the same writer when he says that the arterial supply of the cortex 

 is such that the production of a so-called pure cortical lesion is an anatomical impossibility. 

 ( ' course the same objections, as regards limitation of effect, may be urged against cases 

 of cerebral tumour, haemorrhage, and trauma. 



From the foregoing it is not surprising that mixed conclusions have been drawn from 

 a study of such lesions, and 1 may also venture to say, that it is not altogether safe to 

 utilise such material for purposes of localisation until we acquire more certain information 

 concerning the anatomical distribution of the strands of nerve fibres pertaining to this part 

 and running in the subjacent white substance. For instance, as the centres for the leg, 

 trunk, arm, and face, etc., are separated from one another on the surface, it is more than 

 likely that the strands of fibres conveying impulses from these various areas likewise follow 

 separate paths to the internal capsule, but the exact course which these different strands of 

 fibres pursue, and also the path followed by fibres pertaining to the postcentral gyrus, are 

 unknown to us ; hence it necessarily follows that until we possess this information, and until 

 we can prove by microscopic examination of the brain, in cases of cortical lesion, that the 

 destruction and attendant degeneration is or has been limited to a given set of neurones, 

 clinical observations are bound to be imperfect and inexact. 



In discussing the functions of the postcentral gyrus, further reasons will be advanced 

 for believing that it has nothing to do with the motor function. Here I would say, however, 

 in case the results of the few experimental excitations of the cortex which have been carried 

 out in the human being in bygone years may be brought up in support of the hypothesis 

 of the unity of function of the central gyri, that Professor Sherrington will tell us that in 

 the course of operations which have been recently performed by two surgeons in Berlin 

 and Chicago respectively, stimulation of the cortex by unipolar faradisation has been attended 

 by results which, as regards inexcitability of the postcentral cortex, agree absolutely with 

 those of the anthropoid experiments 1 . 



I have now to mention that although points gleaned from a study of cases at the bedside 

 are inadequate for purposes of precise localisation, information derived in this way has been 

 extremely valuable in assisting us to determine the sequence of representation as regards 

 localisation along the surface extent of the motor area; indeed, it is from careful analysis 

 of such cases that we can now with full certainty state that the sequence in man is 

 identical, for all practical purposes, with that which obtains in the ape. For instance, in the 

 case of the human being, numerous instances of tumour at the vertex and of softening from 

 occlusion of the terminals of the anterior cerebral artery have been collected, during the past 

 tive-and-twenty years, in which destruction of the paracentral lobule and upper fourth of 

 the Rolandic cortex has been adequate to the production of crural monoplegia. 



1 The cases referred to have been quoted in recent papers by Brodmann arid Mills. 



