Minutes of Proceedings. 201 



sulcus appears later than the fissure of Rolando on the human foetal 

 cerebrum, but curiously the opposite is the case in the simian brain, 

 indicating that of the two fissures the intraparietal possesses the 

 greater phylogenetic antiquity. Dr. Cunningham thinks that, by 

 studying the arrangement of its different parts in different ethnic 

 brains, we may be able to poiut to racial distinctions indicated by 

 the varieties. There is another segment of the intraparietal sulcus 

 which Ecker described under the title of sulcus occipitalis tran- 

 versus. This is not, as has been supposed, the homologue of the 

 Affenspalte in the apes, which, as Dr. Cunningham elsewhere shows, 

 is really homologous with the transitory external perpendicular fissure 

 in man. 



In proceeding to study, lastly, the sulci on the external surface of 

 the frontal lobe, we are struck by a remarkable analogy between the 

 prsecentral and the intraparietal sulci. The prsecentral sulcus has 

 two portions corresponding to those of the postcentral ; the former, 

 howerer, unlike the latter, generally remain separate from each other. 

 There are also, in the frontal lobe, furrows which correspond respec- 

 tively to the ramus horizontalis and the ramus occipitalis of the parietal 

 lobe, and a terminal bifurcation of the second of these frontal furrows, 

 corresponding to the sulcus occipitalis transversus. But, according to 

 Dr Cunningham, the morphological relations of these rami in the 

 parietal lobe are quite different from those of the furrows in the 

 frontal lobe which resemble them in form and position. The parietal 

 rami are simultaneously developed, and in the lower primates they are 

 continuous, whilst the two corresponding frontal sulci appear, in 

 general, at different times, and one of them is entirely absent in the 

 lower apes. His view is thus altogether different from that of 

 Eberstaller, from whom he also dissents as to the parallelism of the 

 relation between the first fi'ontal furrow and the sulcus prsecentralis 

 superior with that between the second frontal furrow and the sulcus 

 praecentralis inferior, which two latter sulci he regards as morpho- 

 logically distinct fissural elements, whilst the former two are closely 

 connected, if not to be completely identified. 



On no part of the cerebral surface are the character and mode of 

 development of the sulci so variable as on the frontal lobe. These 

 varieties Dr. Cunningham studies with minute care, and estimates 

 numerically the frequency of the different forms in the brains he has 



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