8 General Remarks on Cortical Fibre and Cell Arrangement [CHAP. 



that region. The paper on the visual area deals with the cortex of " the calcarine fissure 

 and its precincts." His researches on the auditory area have been restricted to an examina- 

 tion of the first temporal convolution, and of the Insula, a part which some include in the 

 auditory sphere. The study of the olfactory region embraces an account of the cortical 

 structure and connections of all the subdivisions of the great limbic lobe. In each branch 

 of the investigation the brains of infants as well as of adults were examined, and for com- 

 parative study, brains of some of the lower animals were employed. Ram<5n y Cajal's work 

 shows blemishes similar to Kaes', for although he describes the histology of these parts in 

 a degree of detail which is almost bewildering, he either gives no boundaries at all, or 

 only draws vague lines round the areas which he has examined with such extraordinary 

 minuteness. 



Passow, who pays a tribute to Kaes' work and follows his methods, has contributed a 

 useful paper on the nerve fibre supply of the two central convolutions (Ascending Frontal 

 and Ascending Parietal). Removing these two convolutions en bloc, he divided them into 

 six equal parts and made serial horizontal sections from top to bottom of each. He states, 

 that proceeding from above downwards, the general fibre wealth of both convolutions gradually 

 increased, reaching a culminating point in the fourth block, it then progressively diminished 

 down to the operculum. He also observed that, in the fourth block, the anterior convolution 

 had a marked advantage over the posterior one in regard to its general supply of fibres. 

 These findings will be criticised later. Two drawings, stated to have been made with the 

 assistance of an ocular micrometer, illustrate Passow's paper, but, being merely composed of 

 a series of vertical and horizontal lines, they are exceedingly diagrammatic. 



Another paper on the central convolutions, most instructive from the localisation point 

 of view, was published as far back as 1879, by Bevan Lewis and Henry Clarke. It dealt 

 with nerve cells, and, as I shall mention later (motor area), these observers seem to have been 

 the first to succeed in defining a functional area on histological grounds. 



Yulpius studied the tangential or association system of fibres in the cortex, and gave an 

 excellent resume of the literature on the subject available at the time he wrote 1892. He 

 recorded the results of an examination of a number of brains taken from persons of varying 

 ages new-born child to old age and the points which he drew attention to were mainly of 

 developmental interest and may be briefly summarised as follows. In the brain of the foetus, 

 born at full time, no medullated nerve fibres are present, excepting in the white substance of 

 the ascending frontal convolution. " Tangential " or association fibres appear in the inner and 

 outer layers of the cortex, at the fourth month, and in the middle layer, at the eighth month. 

 At the 17th year, the development of these fibres is still incomplete, but with the advent of 

 old age they appear to diminish in numerical representation. In criticising this paper, Kaes 

 observes that its value is minimised by the fact that the examination in each instance was 

 so limited the condition of the cortex being studied in six places only this condemnation I 

 am compelled to endorse. 



Frequently quoted as it has been, I cannot refrain from praising the classical work of 

 the late Professor Meynert, published exactly 30 years ago. Although in that paper he dealt 

 more especially with nerve cell lamination, and in it one recognises the original prints of 

 diagrams, which even at the present day find a place in some text-books on the anatomy of 

 the nervous system, yet his researches did include a study of the medullated nerve fibres, 



