iv] Postcentral or Sensory Cortex 93 



The medium sized pyramidal cells had suffered a more manifest reduction in number, and their arrange- 

 ment was disturbed ; furthermore, elements of good shape normally endowed with processes were uncommon. 



It was, however, on the layer of large pyramidal cells so prominent in the normal brain that the chief 

 stress of the affection had fallen. A numerical deficiency was most obvious, fully 50 / 8 of the cells having 

 vanished altogether, and of those that remained only occasionally was one seen which could be described 

 as normal, nearly all were of rounded, oval or irregular shape, and had lost their processes, and although 

 they contained a dislocated nucleus and nucleolus, they appeared pale and homogeneous from loss of their 

 chromophilic particles ; furthermore, they lay scattered about with what appeared to be their apical end 

 pointing in any direction. 



The layer of stellate cells had also suffered severely, not standing out nearly so plainly as it should. 



Not numerous in the normal condition the substellate large pyramidal cells were in this brain practically 

 non-existent. 



The normal columns of fusiform cells were also not to be defined, their place having been taken by 

 atrophied and irregularly placed elements. 



In the sections stained for nerve fibres I could not make sure of definite alteration 1 . 



General Remarks on the Cortical Changes in Tabes Dorsalis. 



I have now examined the cortex cerebri in three cases of Tabes Dorsalis in somewhat 

 close detail, and in all three I have discovered important changes, almost gross in character. 

 Having hitherto escaped notice at the hands of other observers, these changes, in themselves, 

 constitute an interesting addition to our knowledge of the pathology of this disease, and would 

 prove a fruitful topic for discussion in that light. Here, however, I am only concerned with 

 cerebral localisation, and to this my comments must be restricted. Now, to my mind, the 

 evidence derived from a study of these cases may be confidently advanced as stronger than any 

 which has yet been adduced in favour of the assumption that the cortex of the postcentral 

 gyrus, and it alone, is the primary terminus or arrival platform for nerve fibres conveying 

 impulses having to do with " common sensation " ; the data are so clear that they speak for 

 themselves and need little in the way of introduction. For, just as we saw, in the last 

 chapter, that Amyotrophic Lateral Sclerosis, a disease confined exclusively to the muscles and 

 the motor system of neurones, provided a convincing demonstration to the effect that the 

 resulting cortical changes are limited in their distribution to what we may in the future call the 

 " precentral or motor area " ; so we see in Tabes Dorsalis, a disease which is essentially a sensory 

 one, and in typical cases exclusively confined to the sensory system of neurones, just as sharp a 

 limitation of the associated cortical changes to the opposite bank of the Rolandic fissure, to 

 what we may now designate the "postcentral or sensory area." And, conscious as I am 

 that the histological findings on which this weighty statement rests will need to be carefully 

 checked and confirmed by others before it can be considered final, I give it in the firm belief 

 that the portrait received from the microscope is a correct one, and that the solution of a 

 vexatious problem, which has baffled the neurologist for a number of years, is at hand. 



The limitation of the alteration to the postcentral gyrus is the feature of predominant 

 interest, but there are several points of minor importance which arise for consideration in this 

 discussion. The first is that the alterations are still further limited to a certain part of the 



1 In another case of Tabes Dorsalis which has come to hand more recently and presents a repetition of all 

 the cell changes described, examination by the osmium-bichromate method of Marchi has disclose. 1 many acutely 

 degenerated fibres leading to the altered cortex and running iu the subjacent white substance. 



