Many remarkable peculiarities in the shape of the skull, the origin of which cannot be referred to the above-mentioned antagonism between the development of the cranium and that of the facial portion of the skull, depend upon abnormalities and disturbances in the sequence and extent of the ossification of the sutures of the skull. We know that the flat bones of the skull-cap grow principally at the edges, with which they come into contact one with another, and that normally they continue to grow in this way as long as growth continues in the subjacent portions of the brain; but if such a suture undergoes premature ossification, room can only be provided for the growth of the brain by the yielding of one or more of the other sutures, whereby that diameter of the skull at right angles to the yielding suture becomes increased. Thus a skull in which the sagittal or interparietal suture has undergone premature ossification (as often occurs in the Eskimo) assumes the shape of a narrow boat (scaphocephaly).
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.
Now, collections of the skulls of criminals comparatively often contain skulls with a cubic capacity of less that 1,100 c.c., whereas skulls as small as this are hardly ever met with in collections of normal skulls; skulls ranging in cubic capacity from 1,100 c.c. to 1,800 c.c., which in collections of normal skulls are found to the extent of from 6 to 10 per cent., in collections of the skulls of criminals have been present, in various instances, to the extent of 17·8, 18, 65·5, and 72·2 per cent. respectively. Skulls below the normal mean in cubic capacity, which in collections of ordinary skulls are present to the extent of from 25 to 30 per cent., are found in the different collections of the skulls of criminals to be present to the extent of from 30 to 60 per cent. To put the matter in a word, the criminal’s skull is often submicrocephalic; it is, however, necessary to point out that skulls with the very largest cubic capacity, exceeding 1,600 c.c., are met with twice or thrice as often among the skulls of criminals (although this is not true of the Italian collections personally known to me) as they are among bone-dealers’ or museum skulls. A somewhat similar characteristic is exhibited by all the criminal characters accessible to measurement. When the material under investigation is derived indifferently from the general population, the extreme values recorded by measurement are seldom encountered. Among criminals, on the other hand, these extreme values occur much more frequently; and, indeed, the extremely low values are encountered in criminals with especial frequency when the dimension under consideration is one which usually increases as we pass from lower to higher stages in the scale of development. For example, great breadth of the face across the zygomatic arches is a characteristic of lower development; in criminals (900 instances), exceptional width and exceptional narrowness of the face in this region occurs more frequently than in the general population; but this is true to a greater extent as regards the maximal than it is as regards the minimal values of this dimension of the criminal skull.
Similar relations to those which obtain with regard to the size of the skull are found in the bodies of criminals, in respect of the size, or, rather, the weight of the brain, since the mass of the brain must naturally bear a definite relationship to the cubic capacity of the skull. In my “Naturgeschichte des Verbrechers” (“Natural History of the Criminal”), published in 1893, I have collected the data known at that period, derived, for the most part, from Italian sources; these data relate to 305 brains accurately examined. To understand the results here given, it is necessary to remember that the average weight of the European brain, the mean resultant of a very large number of weighings, is 1,360 grammes for males, and 1,220 grammes for females. A maximum very rarely exceeded (though it was exceeded, for example, in the case of Cuvier, and also in that of Tourgeniew) is a brain-weight of 1,800 grammes; whilst the smallest brain-weight known in individuals who can be regarded as having possessed normal intellectual endowments is 960 grammes for males, and 880 grammes for females. Among a very large number of normal brains, we shall find very few indeed weighing as little as 1,150 grammes, and a considerable number weighing more than 1,500 grammes. On the other hand, among the total number of the brains of criminals that have hitherto been weighed, we find that brains weighing less than 1,300 grammes form a very considerable majority; whereas, among the brains of normal individuals, less than 25 per cent. weigh less than 1,300 grammes. In the various collections of the brains of criminals, we find that brains weighing less than 1,300 grammes numbered, in one case, 62·5 per cent. (Benedikt), in a second case, 77 per cent. (Mingazzini), and in a third case, 83·2 per cent. (Mondio).
At the very time when the criminal anthropologists were making a thorough study of this problem, the anatomists (with the exception of Flesch of Wurzburg) and the professorial anthropologists (that is, those in official positions who were interested in this branch of knowledge) were vigorously contesting the idea that there was any difference between the brains of criminals and the so-called normal brains. All the more interesting, therefore, were the data communicated by Professor Johannes Ranke to the German Anthropological Congress at Dortmund in August, 1902, in association with a demonstration of plaster-casts of the heads of decapitated Chinese criminals. According to Ranke, the brains of criminals show no structural deviation from the brains of normal Europeans. This was Professor Ranke’s first contention; but to this there succeeds a little parenthesis, in which he alludes to certain peculiarities in the conformation of the central convolutions. (So, after all, these brains do differ from those of Europeans!) Ranke is straightforward enough to describe the abnormalities in question, but he adds that they are probably to be regarded as racial peculiarities. He gives no grounds whatever for this view, but he prefers to drag in an ethnological hypothesis of this kind rather than to commit himself to the heresy that the brains of criminals exhibit peculiarities; the abnormalities must be labelled “ethnological,” lest they should fall a prize to the heretical school of Lombroso.
On the other hand, in the same address (1902), Ranke laid stress on the fact that among the brains of criminals there is a preponderance of exceptionally large and of abnormally small brains, and also that among the skulls of criminals there is, similarly, a marked preponderance of extremely large and extremely small skulls—a fact which he might have ascertained as long ago as 1893 from a study of the very numerous tables of measurements and weights published in my “Natural History of the Criminal.”
Finally, in other portions of his address, Ranke approximates even more closely to the “heresies” of criminal anthropology. He insists on the need for a careful study of the brains of criminals, and he points out that there are two questions to which especial attention should be paid in future investigations of this kind. The first of these is the question whether the possessor of a brain of medium size does not exhibit less inclination to crime than one whose brain is either excessively large or excessively small; and the second is the question whether, perhaps, certain intellectual abnormalities, which readily lead to criminal practices, may not depend upon a partial microcephaly—that is to say, is it not possible that in certain sharply circumscribed portions of the brain, during intra-uterine life, there may have developed certain abnormalities corresponding to those characteristic of microcephaly? According to Ranke, it is always possible that an indirect connection exists between the so-called stenocrotaphy (narrowing of the skull in the temporal region) and the criminal tendency, in so far as, in consequence of the said narrowing of the skull, those nervous centres by whose activity automatism is kept within bounds may have their development partially arrested or may in some other way be sympathetically affected.