Skull and crossbones

“ A great deal of the endless variety in the form of the skull of different mammals depends upon the differing proportions of cranium and face. In the human skull, for example, the cranium is enormously developed and forms a great dome, while the face is shortened almost to the limit of possibility; the skull of the Horse, on the other hand, goes to nearly the opposite extreme of elongation of the facial and shortening of the cranial region. The posterior surface of the skull, or occiput, is made up of four bones, which in most adult mammals are fused into a single occipital bone. ”

“ Tackling his main problem of the unity of plan of the vertebrate skull, Huxley shows, by a careful discussion of the anatomical relationships of the chief bones in typical examples of all vertebrate classes, that there is on the whole unity of plan as regards the osseous skull. This unity of composition can be established, on the gradation method, by considering the connections of the bones of the skull with one another, their relations to the parts of the brain and to the foramina of the principal cranial nerves. ”

“ The skull is built up of longitudinal cartilaginous pieces, now known as the "parachordals" and "trabeculæ," of sense capsules enclosing the nose and ear, and of various roofing bones. In the historical development of the skull three grades become apparent; a primitive stage, as seen in Amphioxus, where there is nothing but a fibrous investment of the nervous structures; a cartilaginous grade, as seen in the skate or shark, where the skull is formed of cartilage, very imperfectly hardened by earthy deposits; a bony stage, seen in most of the higher animals. ”

“ But macrodonts are often microcephalic, and therefore the frontal region of the skull must be adjusted to form a foundation for this arch. In the average English male skull, held with its visual axes horizontal, a perpendicular dropped from the anterior surface of the fronto-nasal suture will cut the plane of the alveolar arch between the premolar teeth or through the first premolar. In an Australian skull the perpendicular cuts the horizontal plane at the anterior border of the first molar teeth. ”

“ Although the bones of the skull are so large, they are not solid, their interior being occupied by hollows divided from each other by thin partitions, by which means the skull is rendered lighter than might be supposed; and altogether it forms a beautiful instance of a provision for increasing the surface for attachment of muscles, without being too great a burden to its possessor. ”

“ If the impaction take place owing to the head being larger than natural, if it be a hydrocephalous fœtus, we must open its skull with a polypus-scalpel, or a needle, or a sharp-pointed knife concealed between the fingers, in order that it may collapse when evacuated; but if it be a naturally large head, we must open the skull in like manner, and break down its bones with a tooth-forceps or a bone-forceps, and if the bones project they ought to be extracted. ”

“ Now, those skulls which have the largest and strongest jaws and the widest zygomatic aperture, have the muscles so large that they meet on the crown of the skull, and deposit the bony ridge which separates them, and which is the highest in that which has the smallest cranial surface. In those which combine a large surface with comparatively weak jaws, and small zygomatic aperture, the muscles, on each side, do not extend to the crown, a space of from 1 to 2 inches remaining between them, and along their margins small ridges are formed. ”

“ Nostrils represented by the single or double blow-hole, nearly always situated far back upon the skull. Bones of loose texture and much impregnated with oil. The skull has a greatly-developed facial portion; supra-occipital bones meeting the frontal by overgrowing, or growing in between the parietals; bones surrounding the organ of hearing loosely attached to the skull, the tympanics of peculiar cowrie-shell form. Coronoid process of mandible absent, or very feebly developed. ”

“ Convolutions that are frequently called into action become better supplied with arterial blood, expand and grow, while the adjacent portion of the inner plate of the skull becomes absorbed, and presents a remarkable indentation. Convolutions that are seldom in action shrink in size, and the adjacent bone grows in upon them. Thus the skull becomes thinner at the site of every active organ, and thicker over every convolution that is inactive. ”

“ The skull consists of a cartilaginous cranium, and of jaw and visceral arches. The cranium persists throughout life, in what closely resembles a transitory embryonic condition of the higher types. There is a nasal capsule (na.c.) , a brain case proper, and lateral otic (auditory) capsules (ot.c.) containing the internal ear. (This should be compared with the frog's embryonic skull.) The upper jaw has a great bar of cartilage, the palato-pterygoid, as its sole support; the arch of premaxilla, maxilla, jugal, and squamosal-- all membrane bones-- is, of course, not represented. ”

“ It must be noted that many of these features may be found also in recent human skulls of the inferior races, but that they are very rare, very scattered, very isolated, and occur only as aberrations. It is the accumulation of all these features in every skull of a whole series which constitutes an assemblage entirely new and of great importance. ”

“ So far from being able to make a trustworthy reconstruction from a few scattered bones, competent palæontologists have been sometimes led completely astray in associating the separated parts of the same skeleton. More than once it has happened that the dissociated skull and feet [42] of one and the same animal have been assigned to entirely different groups, just because no one could have ventured, in advance of experience, to suppose that such a skull and teeth could belong to a creature with such feet. ”

“ The base-line of the skull, so far from "varying irregularly," varies not at all, but is always straight, and in the most natural position of the head is always horizontal, while the frontal line of the face and the dorsal line of the body diverge more and more from the horizontal, and become more and more irregular in figure. ”

“ If the skull and leg bones that belong in a skin are missing, I invariably carve others of the same size out of soft pine to replace the lost members. These bones are imperatively necessary to give shape and length to the various joints and angles of the limbs, to shape the head, to give a foundation for the attachment of wires, and to build upon generally. Very often the skull of an animal is of such value to science that it must be kept out of the skin at all hazards, and exhibited separately. ”

“ The skeleton is bony, but in the skull much cartilage generally remains. The vertebral centra are usually deeply biconcave, and the tail is of the masked heterocercal type distinguished as homocercal. In the skull the occipital region is always completely ossified, while the sphenoidal region is generally less ossified. The skull has usually a very large number of membrane bones developed in connection with it. The teeth vary much in character in the different members of the order, but are as a rule numerous and pointed, and are ankylosed to the bone. ”

“ When the skull-cap is ready to come off one will feel it 'wobble.' Insert then the hook under its forward end and pull firmly. The bony skull-cap alone will come away, leaving the periosteum of the inner surface adhering to that of the base of the skull, enveloping the brain, and forming the so-called dura mater or outer one of its 'meninges.' This dura mater should be slit open round the margins, when the brain will be exposed wrapped in its nearest membrane, the pia mater, full of blood-vessels whose branches penetrate the tissues. ”

“ The skull is large and solid, with no front teeth; the vertebræ extend to the very tip of the tail, but show no rudiments of posterior limbs; the fore limbs, on the contrary, are very highly developed, the bones exactly corresponding to those of the human arm, having even the five fingers, with every joint distinct, yet enclosed in a stiff inflexible skin, where not a joint can have any motion. ”

“ The skull, and all the other parts of the skeleton, are generally light and delicate in their construction, as might be expected in animals destined to support themselves in the air; but there is no trace of those pneumatic cavities which, in birds, enable the air to penetrate all parts of the skeleton. The jaws are well armed with teeth, which differ in their character in accordance with the food consumed by the animals. The ribs are well developed, and enclose a large chest cavity. ”

“ These are large bones which, after roofing over the cranial cavity, extend upwards and become expanded into a pair of broad plates which unite with the squamosal and bones of the frontal segment to form a wide, solid, false roof to the skull. ”

“ The enormous tusks, with their powerful leverage, the massive teeth, and the large and weighty proboscis,{32} require a corresponding supply of muscles, and consequently a large surface of bone for the attachments of these muscles. Now, were the skull solid in proportion to its requisite size, its weight would be too much for the neck to endure, however short and sturdy it might be. The mode of attaining expanse of surface, together with lightness of structure, is singularly beautiful. ”

“ This skeleton is that of a large and powerfully built man, the bones being very heavy and strong with marked impressions and prominences for muscular attachment. The skeleton, with the exception of some of the small bones of the hands and feet is complete.
The skull is large and massive, and the lower jaw very strong and heavy. ”

“ On removing the upper of these two stalagmitic floors a perfect human skull was discovered, along with broken bones of animals, charcoal, limpet shells, bone pins, an instrument of bone like a paper-knife, coarse pottery with fragments of chert imbedded in its mass, a portion of a jet armlet, as well as several boars’ tusks. ”

“ And now, to return to the fossil skulls, and to the rank which they occupy among, or beyond, these existing varieties of cranial conformation. In the first place, I must remark, that, as Professor Schmerling well observed ('supra', p. 300) in commenting upon the Engis skull, the formation of a safe judgment upon the question is greatly hindered by the absence of the jaws from both the crania, so that there is no means of deciding with certainty, whether they were more or less prognathous than the lower existing races of mankind. ”

“ A few anatomists hold that the fragments are parts of a human skeleton; according to others there is no doubt but that they belonged to individuals of the same race. Others, again, consider the femur to be quite human, while they think that the skullcap and the teeth must have belonged to the most anthropoid of all anthropoid apes. A few anatomists, however, agree with me in the opinion that a femur entirely human in character might nevertheless belong to the same individual as this ape-like skull, because a similar function would entail a similar form. ”

“ Lately science has perfected the difficult process of reconstructing the faces of human beings of whom only the skull or a few bones, perhaps, are obtainable.
"To the unskilled observer a fleshless skull presents little human likeness and certainly conveys no notion of the exact appearance in life of the person to whom it belonged. But by an ingenious system of building up muscles and skin upon the bones of the skull this appearance can be reproduced with scientific accuracy. ”