TRANSACTIONS OF SECTION H. 903 



3. On certain Markings on the Frontal Fart of the Human Cranium^ and 

 their Significance. By A. Francis Dixon. 



An examination of the frontal region of tlie cranium shows that, in many cases, 

 grooves or channels are present on the bone, corresponding to the branches of the 

 supra-orbital nerves. These grooves vary very much in appearance, as thej- may 

 be simple or branched, shallov? or deeply cut. They are not infrequently converted 

 in parts of their course into little tunnels. In some cases they are found on one 

 side of the cranium only, in others they occur or both sides ; their distribution is 

 very rarely quite symmetrical. Most frequently the grooves occur beneath 

 the outer branches of the supra-orbital nerve, but in many cases they are found 

 beneath the inner branches. The grooves never pass from the frontal on to the 

 parietal bone — across the coronal suture. They often extend upwards from the 

 supra-orbital notch, or foramen, as far as the coronal suture; in other cases they 

 begin inferiorly at a little foramen where some branch of the nerve enters the bone. 

 The openings of these little foramina are directed upwards towards the coronal 

 suture, just as the openings of the nutrient foramina in the long bones are 

 directed towards the end of the bone where growth is most active and goes 

 on longest. 



The presence of these grooves indicates a want in proportion between the growth 

 in length of the 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. The constricting 

 portions of the nerves are often limited inferiorly at a point where some little 

 branch enters the bone, and superiorly at the coronal suture, where the deep 

 layers of scalp are firmly bound down to the cranium. Hence the grooves for the 

 nerves do not cross the coronal suture and often begin inferiorly at little foramina 

 whose openings are directed upwards. The grooves appear to indicate in the 

 skulls in which they occur an excessive development of the frontal part of the 

 cranial wall. In races in whom the grooves are common, and strongly marked, 

 we would expect the presence of a tendency towards increased development and 

 capacity of the frontal part of the cranium ; while, 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 much uniformity in the shape and size of the cranium, 

 indicating that none of its various parts are tending towards an increased develop- 

 ment. In the purer races of mankind, with marked uniformity in the size and 

 shape of their crania, we would look for the greatest harmony between the growth 

 in length of the overlying structures and the amount of expansion of the 

 various parts of the cranial wall ; on the other hand, in mixed races we would be 

 more likely to find individuals exhibiting a want of such correspondence in the 

 amount of growth of the superficial and deeper structures. In this connection it 

 is interesting to note that the frontal grooves are almost never found in Australian, 

 and Tasmanian skulls, that they are rare among Melanesians, slightly more common 

 among Polynesians, while among Bushmen and Negroes, especially in Zulus and 

 Kaffirs, they are very common, and often extraordinarily well marked. Among 

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

 skulls obtained in the dissecting room they are present in about 41 per cent, 

 of all cases. 



4. On the Sacral Index. By Professor D. J. Cunningham, M.D., F.R.S. 



Inasmuch as the true length of the sacral portion of the vertebral column is 

 not indicated by the shortest distance between the apex and base of the sacrum, 

 but rather by the length of the curve formed by the sacral vertebrae, it is proposed 

 that, in making measurements for the determination of a sacral index, * length ' 

 should be measured by using a tape along the concavity of the sacral curve, and 

 not by calipers, one limb of which is placed upon the base and the other on the 

 g,pex of the pacfuni. Breadth (measured by calipers in th§ oydjn^rj piftpner) 



