It is probable that such sutural varieties are dependent upon the most diverse causes, and that in many cases they are not anomalies, but racial peculiarities or racial congenital variations, whose origin is genetically very ancient. In the skulls of criminals examined for the detection of sutural abnormalities these have been found in about 40 per cent., whilst in 1,200 living criminals the frequency was as high as 49 per cent. Among the most interesting of the sutural abnormalities are the “Wormian bones,” by which more or less extensive deficiencies of bone along the principal sutures are filled in. A Wormian bone found at the apex of the lambdoid suture, where this joins the posterior extremity of the sagittal suture, was first discovered in the mummies of the ancient civilized race of Peru, and it has therefore been named the “Inca bone.” It is said that all the infant Inca mummies possess this bone, and that it is present in 15 to 20 per cent. of the adult Inca remains. Italian observers found it in 25 per cent. of the skulls of murderers, and in 8 per cent. of the skulls of other criminals.[12] Certain other peculiarities of the sutures of the skull have received much attention from students of general anthropology, on account of the fact that they constitute distinctive racial characters; but some of these are met with even more frequently in the skulls of criminals than in ethnological specimens, although their appearance in these latter is considered a characteristic feature of normal anthropology. Of great interest are measurements of the cubical capacity of dried skulls, and also estimates of this capacity, based upon measurements of the head taken in living criminals (although such estimates can be no more than approximations). Be it noted in this connection that the extreme recorded range of capacity of normal skulls is from 2,050 c.c. (the largest) to 1,050 c.c. (the smallest); the largest recorded cubic capacity of skull in an anthropoid ape is 621 c.c.; thus, the difference between the cubic capacity of the largest and that of the smallest human skull exceeds the difference between the cubic capacity of the smallest human skull and that of the largest simian skull.