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any description is to he seen throughout the cortex of either of these animals until about the 

 eighth day of life. Further, in the human body, the fibres of the pyramidal tract, in its spinal course, 

 do in >t acquire their sheath of medulla until long after the posterior column fibres, and one 

 would have thought that this sequence of events would have enabled Flechsig and the Vogts to 

 distinguish readily between sensory and motor fibres in the developing human cortex. This, 

 apparently, was not the case. The probable key to the difficulty is to be found in the assumption, 

 that the process of medullation in any given fibre does not arise simultaneously along its whole 

 length, but begins at the end next the cell giving origin to it, and from there spreads onwards 

 (I understand that this is an accepted belief) and so, on inspecting cortex from the Rolandic 

 region in Man, or the cruciate zone in lower animals, the embryologist might confuse the first 

 segment of a motor fibre, beginning to myelinate, with the terminal of a sensory fibre, just being 

 completed. 



We can now turn to the fissural homologies connected with this area. The supposed ante- 

 cedents of the fissure of Rolando have already been considered under the motor area, but I would 

 here add that Tscherrnak's investigations make him a firm supporter of Meynert's old-standing 

 contention, that the sulcus coronalis is the homologue of the fissure of Rolando. With this, as 

 already mentioned, I can only agree in part, believing that the sulcus coronalis is the antecedent of 

 the lower segment only of Rolando, and the compensatory fissure unnoticed by Tschermak the 

 representative of the upper segment. To Tschermak's contingent assertion, however, that the field 

 behind, the area which forms the subject of this discussion, is homologous witli the gyrus centralis 

 posterior hominis, I unreservedly give support. 



We have next to find the forerunner of the postcentral fissural system. This is not easy. In 

 the .summarised account of his examination of the magnificent collection of brains in the Royal 

 College of Surgeons' Museum, I notice that Dr Elliot Smith credits the ansate fissure with becoming 

 the sulcus postcentralis superior, and it is given as a moot point, whether the sulcus coronalis is 

 the antecedent of the sulcus postcentralis inferior. But from what is written in the foregoing 

 paragraphs, neither does histology allot a place in the formation to the sulcus coronalis, nor do I 

 see the necessity for giving the upper constituent of the fissure preeminence and regarding it as 

 the sole derivative of the ansate sulcus. The question is, without doubt, one of considerable 

 difficulty, and, to my mind, as yet insufficiently studied, but judging from its relation to "sensory" 

 cortex, and its apparently intimate connection with the lateral fissure, I prefer to regard the ansate 

 sulcus mainly as the forerunner of the inferior segment, or possibly of the united system, since, in 

 Man and the higher apes, both constituents are more often than not continuous. 



The peculiar arrangement of parts in the brain of Sus calls for special consideration. For if 

 in our attempt to adjust the physiological findings we follow the recognised sulcal nomenclature, we 

 soon find ourselves in inextricable confusion. The first point to be called in question is whether 

 the fissure, accepted by the comparative anatomist as the coronal (marked Coronal 1 in my 

 figures), is correctly so named. I think not. Its relation to what I take to be the motor and 

 sensory areas, its dorsal position on the hemisphere, its position in relation to other fissures, notably 

 the intercalary and orbital, might all be used in arguing against such an homology. The pig's is 

 a highly macrosmatic as well as a strong visual brain, it likewise has a bulky gyrus fornicatus, 

 and one consequence of these' combined properties is that all those sulci, and the contingent 

 functional areas, on the dorsum and convexity of the hemisphere, have the appearance of being 

 rotated outwards on the sagittal axis. The coronal sulcus, instead of being brought closer to the 

 upper margin of the hemisphere, is further removed. For this and other reasons mentioned, I 

 venture to say that the cross-shaped fissure (marked coronal, with a note of interrogation) in my 

 diagram of the lateral surface of the pig's brain is the true coronal, while in the sulcus of other 

 authors I see one which might be the homologue of the sulcus cruciatus. Of course, I am aware 



