x] Frontal and Prefrontal Areas 245 



Without for a moment discrediting the accuracy of Bolton's observations, and while ad- 

 miring the work for the care bestowed upon it, I must nevertheless say that his arguments 

 seem to rest on frail premises. It is agreed from personal experience that the regions he 

 indicates are those which apparently present the greatest atrophy in dementia, and that 

 the prefrontal region suffers in particular, but it is not granted that the cerebral changes 

 of dementia are confined to these parts and that there are not grave changes in other regions 

 upon which the mental condition may in equal degree rest. Indeed in the dementia of 

 general paralysis, one of the conditions which he has selected for study, we have very good 

 reasons for supposing that the morbid process has a tendency to be ubiquitous, and yet in 

 given cases of this disease in which our microscopic examination proves the universality of 

 the cortical affection, we might still be correct in describing the prefrontal region, etc., as 

 the parts which to the naked eye exhibit most atrophy, and the same might apply to ordinary 

 forms of dementia. Now my major point is that a fundamental physical reason may be 

 brought forward to explain this anomaly, and it deserves most careful consideration in the 

 process of formulating conclusions on naked-eye appearances. It turns on the architecture 

 of the cortex, and particularly on the framework of nerve fibres upon which the cortex is 

 built : thus, viewed in relation to structure those convolutions having cortex supported by stout 

 radiary projections and a strong interradiary plexus, for instance, the precentral and occipital 

 gvri, will naturally exhibit least macroscopic change, whereas those with attenuated and 

 collapsible radiations and an interradiary network untraversed by strong fibres, the " prefrontal " 

 region more than any other possesses these characters, will on the contrary show most. Long 

 before Bolton's paper appeared I was struck with this association, and had even seen it 

 illustrated, but of course not to a grave extent, in the brains of individuals who had suffered 

 from a minimum of mental disease, but in whom death was brought about by physical 

 disease causing general bodily emaciation. Indeed, proof on this point could be multiplied 

 interminably. My contention therefore is, that given a morbid process universally distributed 

 over the cortex, and affecting the pyramidal cells or any other system equally throughout, 

 then the parts showing most atrophy to the naked eye will be those of weak architecture, 

 and exactly those to which Bolton has specially drawn attention. 



In the next place it cannot be conceded that cortical measurements in themselves supply 

 an accurate means for estimating degrees of structural disintegration. Bolton leads us to 

 assume that the reduction in depth of the conjoint layers of pyramidal cells external to the 

 stellate layer is the result of disappearance of these cells, but he does not prove this, and 

 cannot until he supplements his measurements by comparative cell counts (an enormous task, 

 almost impossible to perform thoroughly), and so excludes the effects of condensation. For 

 surely condensation is an important factor to reckon with ; moreover, for the structural reasons 

 mentioned above, we should expect the same change to be specially pronounced in the 

 "prefrontal" area and in others built on a frail plan. 



Mention of condensation makes one think too of what happens, in the process of cortical 

 wasting, to that substance remaining over when cells, fibres, and neuroglia are removed. Also, 

 of other agencies which may influence the topographical distribution of cerebral atrophy and 

 which we are compelled to bear in mind in the examination of the brain, the nutritional 

 supply and the influence of gravity are of importance. 



Therefore I think that the grounds on which Bolton bases his arguments are untenable, 

 and that the evidence he adduces affords little help in enabling us to arrive at the correct 

 function of the frontal lobes. 



