Jawbone

“ At length in the most venomous of the whole Order, the upper jawbone is reduced to a small size, carrying a single curved and tubular tooth of great length, which is followed only by others of the same structure, undeveloped, and destined to replace it after its loss by decay or violence. ”

“ These two bones, which hold the four upper cutting teeth, are recognized without difficulty in most mammals; in man, however, they were at that time unknown, and celebrated comparative anatomists even laid great stress upon this want of a mid jawbone, as they considered it to constitute the principal difference between men and apes—the want of a mid jawbone was, curiously enough, looked upon as the most human of all human characteristics. ”

“ TEETH OF IGUANA.
attached to the inner edge of the jawbone, which for the most part are lobed or dilated, and have a crenated or notched edge. Besides these distinctions, the body is covered with scales or tubercles, often ridged or spinous, always horny in texture, not bony: those of the head frequently take the form of many-sided plates, more or less large, and those of the belly are square and overlapping. ”

“ They are huge implements, four or five times as big as those made by any known race of true men, and they are not ill made. Certainly some creature with an intelligent brain made them. Big clumsy hands must have gripped and used these rocky chunks. But so far only one small fragment of a skeleton of this age has been found, a very massive chinless lower jawbone, with teeth rather more specialized than those of men to-day. We can only guess what strange foreshadowing of the human form once ate with that jaw and struck at its enemies with those big but not unhandy flint blades. ”

“ The jawbones are strong, supporting remarkably firm and commonly regular teeth. In the youthful these are in general white, but toward middle age they have lost their enamel and become black or are worn down to the gums. ”

“ Their effect is to increase greatly the surface over which the air that is breathed must pass, enabling it to become both warm and moist before entering the lungs. The jaw bones serve as receptacles for the teeth; the lower jaw, which is the only movable bone of the head, except for the tiny bones within the ears, has also the duty of operating as a mill in reducing the food to suitable form for swallowing. To aid in this function the lower jaw is hinged to the rest of the skull in such a way that it not only opens and closes but can slide forward and back or from side to side. ”

“ Location.—The inferior maxilla, lower jaw, or os maxillare inferius, also called the mandibular bone, or pars dentis, is analogous to the lower jaw of mammals. It articulates posteriorly with the quadrate bone.
Description.—The inferior maxilla is the largest bone of the face. It is made up of a right and a left limb which are separate in the fetus and which unite subsequently anteriorly, forming the inferior portion of the beak. Each limb of the jaw is developed from five elements: the pars articularis, which forms the jaw-joint and, expanded, articulates with the quadrate bone ”

“ In old males the length of face is much greater than one-half, and the front of the upper jaw is stuck out considerably. But in all there is a swelling of the upper jaw-bone, just in front of the orbit and on each side of the nose-bones, which sometimes is vast and at others turned into a ridge. ”

“ The professor would also suggest a little less cheekbone. Cheekbones are being worn low this season.
Will the lady have a dimpled chin, or does she fancy the square-cut jaw? Maybe the square-cut jaw and the firm, sweet mouth are more suitable for the married woman. They go well enough with the baby and the tea-urn, and the strong, proud man in the background. For the unmarried girl the dimpled chin and the rosebud mouth are, perhaps, on the whole safer. Some gentlemen are so nervous of that firm, square jaw. For the present, at all events, let us keep to the rosebud and the dimple. ”

“ The upper jaw bone is the most complex of all the bones of the face. Looking at its central part or body we are first of all struck with the cavity in it—the antrum of Highmore. Now, if you take a hundred bones, you will not be able to find two antra exactly alike, but they will differ in size, in shape, in depth, in width, and in size of their angles and inclination of each of their walls. And all these peculiarities influence the countenance, and must, therefore, be studied before you can hope to be successful in replacing the lost dental organs. ”

“ For years the workmen had been instructed to keep a sharp lookout for human remains. The jaw had evidently drifted down with the river sands and had become separated from the skull, but it remained in perfect preservation. The author's description may first be quoted. (36) The mandible shows a combination of features never before found in any fossil or recent man. The protrusion of the lower jaw just below the front teeth which gives shape to the human chin is entirely lacking. ”

“ Adjust the skin so that it fits naturally and easily on the skull and around the mouth, and see that the eyes come over the centre of the orbits. If the clay which was put upon the skull does not fill out the jaws and sides of the head quite naturally, push in a little chopped tow until the proper form is obtained.
Fig. 27.—The Finished Specimen.
Avoid getting one jaw fuller than the other; it is only boys and men who chew tobacco who have cheeks that are not bilaterally symmetrical. Avoid getting one eye too far back, forward, up or down, but match the one that is correctly placed. ”

“ His facial and jaw-bones are smaller, and project far less, even in the most prognathous of men, than in the Apes; the lower front margin of the under jaw is characteristically human, being produced forward to form the chin. In the human skull there is always a spike-like bone—the styloid process—dependent from and ossified to the ear-bones.
In Man the form of the pelvis—the large osseous block to which the legs are articulated—is very characteristic in its width; its great basin-shaped cavity receives and supports his lower internal organs ”

“ Finally, prominent cheek-bones are objectionable because they are concomitants of the large, clumsy, brutal jaws which characterise savages and apes. To the cheek-bones the upper jaw-bone is directly attached; hence the larger the teeth are, and the more vigorously they are exercised in fighting and picking bones, the more massive must be the cheek-bones, to prevent the upper jaw from being pushed out of position. ”

“ This jaw-bone was found in a sandpit near Heidelberg, at a depth of eighty feet from the surface, [26] and it is not the jaw-bone of a man as we understand man, but it is man-like in every respect, except that it has absolutely no trace of a chin; it is more massive than a man’s, and its narrowness behind could not, it is thought, have given the tongue sufficient play for articulate speech. ”

“ Running between and from the pectoral fins a thick, fleshy process continues right up underneath the jaw. As the included flesh is contained in a remarkably thin silvery skin, extraordinary care is necessary in freeing this from the flesh, so the knife, the scraper, and the fingers will all have to come into play. It is held at the extreme end under the jaw by a thin bone, which, though skinned to its under part, must not be cut away, but left slightly attached. ”

“ Influence of mastication on the jaw-bones.—It is well known that the size of a bone is largely determined by the degree to which the muscles attached to it are exercised. That the jaws do not grow to their normal size, if not adequately exercised during their period of growth, is strikingly shown by the overcrowding of the teeth, which takes place in those brought up on soft foods, and this even though there be no contraction of the jaws resulting from mouth-breathing. ”

“ The combined characters of the jaw, molars and skull were made the basis of a genus Eoanthropus, placed in the family Hominidæ.... While the brain case is human in structure, the jaw and teeth have not yet been shown to present any character diagnostic of man; the recognized features in which they resemble human jaws and teeth are merely those which men and apes possess in common. On the other hand, the symphyseal region of the jaw, the canine tooth and the molars are unlike those known to occur in any race of men.... ”

“ 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. ”

“ The skeleton is cartilaginous, the skull without sutures, and the notochord more or less fully replaced or inclosed by vertebral segments. The jaws are peculiar in structure, as are also the teeth, which are usually highly specialized and found on the jaws only. There are no membrane bones; the shoulder-girdle is well developed, each half of one piece of cartilage, and the ventral fins, with the pelvic-girdle, are always present, always many-rayed, and abdominal in position. The skin is covered with placoid scales, or shagreen, or with bony bucklers, or else it is naked. ”

“ Having therefore first shaven the hairs about the forehead, we must permit the lower jaw to move, and avoiding the place where the temporal muscles are seen to act, we are to make three straight and parallel incisions on the forehead, each having the length of two fingers, and descending to the bone, and being at the distance of about three fingers’ breadth from one another. ”

“ The two fore-teeth of their upper jaw are wanting in all of them, men and women, old and young; whether they draw them out, I know not: neither have they any beards. They are long-visaged, and of a very unpleasant aspect, having no one graceful feature in their faces. ”

“ The articulation of the inferior maxillary, or lower jaw bone, with the zygomatic process of the temporal bone, in flesh-eating animals, is such as to permit the direct or cutting motion, but prevent the lateral or grinding, which latter is the principal motion in man and other plant-eating creatures. ”

“ We can hardly suppose that disuse would maintain or develop the projecting chin, increase its perpendicular height till the jaw is deepest and strongest at its extremity, evolve a side flange, and enlarge [10] the upper jaw-bone to form part of a more prominent nose, while drawing back the savagely obtrusive teeth and lips to a more pleasing and subdued position of retirement and of humanized beauty. ”