ANATOMICAL SOCIETY OF GREAT BRITAIN AND IRELAND. ll 



or foramen, as far as the coronal suture ; but in other cases they begin 

 inferiorly at a Httle foramen, where some branch of the nerve enters 

 the bone. In the majority of cases they do not reach as far as the 

 coronal suture. The formation of the grooves indicates a want of pro- 

 portion between the growth in length of the overlying nerves and the 

 amount of expansion of the underlying part of the cranium. The 

 nerves might be looked upon as constricting cords, which become 

 depressed in the developing bone as the cranium expands. Their 

 formation is comparable to that of the grooves and tunnels sometimes 

 found in the clavicle for the descending supraclavicular branches of 

 the cervical plexus. The constricting portion of the nerve is often 

 limited superiorly at the coronal suture, where the deep layers of the 

 scalp are tirmly bound down to the cranial wall, and inferiorly at a 

 point where a branch of the nerve enters the bone. Hence the grooves 

 caused by the nerves do not cross the coronal suture, even when they 

 reach as far as it, and they often end below at a little foramen in the 

 bone. The openings of these little foramina are directed upwards 

 towards the coronal suture, just as the openings of the nutrient 

 foramina of the long bones are directed towards the part of the bone 

 where growth is most active and goes on longest. The presence of 

 the grooves may be taken to indicate an excessive development of the 

 frontal part of the cranium. In those races in whom the grooves are 

 common and strongly marked, we would expect to find a tendency 

 towards increased development and capacity of the frontal part of the 

 cranium. On the other hand, in races in whom the grooves do not 

 occur, or are rare and but feebly marked, we would expect to find a 

 greater uniformity in the shape and size of the cranium, since in these 

 complete harmony exists between the rate and amount of growth of 

 the nerves and that of the underlying frontal region of the cranium. 

 In this connection it is interesting to find that these frontal grooves 

 are almost never found in Australian and Tasmanian crania, that they 

 are rare among Melanesians, sHghtly more common in Polynesians, 

 while in Negroes and Bushmen they are very common. Among 

 Negroes they are present in over 50 per cent, of the skulls examined, 

 and in many cases they are extraordinarily well marked. In ordinary 

 dissecting-room crania they are present in slightly over 40 per cent, of 

 all cases, and are sometimes very marked. 



In the parietal region of the cranium, grooves for the middle tem- 

 poral artery were found to be especially well marked in many of the 

 most brachycephalic Burmese skulls. Some of these crania appear to 

 have been artificially deformed, and the marked development of the 

 grooves probably indicates a want of proportion in the length of the 

 artery, and the amount of expansion of the parietal region of the 

 cranium in these skulls. 



In several young skulls (of about 3-5 years) distinct grooves for 

 vessels were found in the occipital region. These are present on the 

 surface of the cranium, between the superior and highest curved lines of 

 the occipital bone. In all the specimens which showed these mark- 

 ings, the interval between the curved hues was not only relatively 



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