Mandible

“ As the jaws recede and the cranium augments, the forehead rises, the nose becomes vertical, and when the mandible has retreated beyond the frontal limit, the wide yawning mouth has been reduced in size, while a new formation has appeared below it—the chin. ”

“ Body large and heavy; upper mandible depressed, narrower and higher at base, broader and flattened toward the end, composed of a median bar, continuing the whole length of the bill and terminating in a strongly hooked nail, and of two lateral portions each separated from the median bar by a very narrow groove, in the basal part of which the small nostril opens; lower mandible thin, of two flexible arches supporting a large pouch of naked membrane. ”

“ To the lower mandible, in place of the skin or membrane filling up the angle in most other birds, is appended a vast sac seven inches in depth opposite the base of the bill, and extending down the throat about eight inches, so that its length from the tip of the lower mandible is twenty-one and a half inches. It is formed of the skin, which is thin, transparent, elastic, rugous, highly vascular, and capable of being expanded like a net, supported by the elastic mandibles to the breadth of nine and a half inches. ”

“ The strength of the mandible may be measured directly in various locations on the body. Due to the peculiar build of the body, however, and especially to its variations, these measurements are by no means simple and wholly satisfactory. ”

“ The mandible is usually as long as the skull and is slender. It is composed of 6 elements so far as known (465) ; these are the articular, the surangular, the angular, the coronoid, the dentary, and the splenial. Other elements may be present, but the anatomy of this portion of the animals is not very completely known. The bones are sculptured and cut by lateral-line canals (458) in a few forms. Whether the articular operated on an osseous or cartilaginous quadrate is unknown, though certain specimens seem to indicate an osseous condition for that element. ”

“ Lower mandible straight, the dorsal line at the base sloping upwards, at one-third of the length of the bill bulging, then straightish and slightly ascending, the tip narrower than that of the upper mandible, the sides at the base sloping upwards, and having a shallow groove, towards the end becoming perpendicular. ”

“ The articulation of the mandible to the quadrate-bone is such as to allow of a very considerable amount of lateral play, and, by a particular arrangement of the muscles which move the former, it comes to pass that so soon as the bird opens its mouth the point of the mandible is brought immediately opposite to that of the maxilla (which itself is movable vertically) , instead of crossing or overlapping it—the usual position when the mouth is closed. ”

“ II. Quadrate suspended from the supratemporal; mandible at least as long as the skull; pterygoids extending to quadrate or mandible.
46 A. Mandible with coronoid bone; nasals in sutural contact with frontals and prefrontals; transverse bone short, not projecting much beyond cranium; maxillary not half as long as mandible, which is not longer than skull (to occiput)
Eryx. ”

“ MANDIBLES, in Insects—The first or uppermost pair of jaws, which are generally solid, horny, biting organs. In birds the term is applied to both jaws with their horny coverings. In quadrupeds the mandible is properly the lower jaw. ”

“ Bill short, robust, conical, acute; upper mandible straight in the dorsal outline, angular, and encroaching a little on the forehead, broader than the lower, acute and inflected on the edges; lower mandible also inflected at the edges; the gap-line deflected at the base. Head rather large, neck short, body full. ”

“ The mandible is composed of several bones as in reptiles. The os articulare bears on its inner side the inner mandibular process which serves for the insertion of part of the digastric muscle or opener of the mouth; another portion of this muscle is attached to the os angulare, which frequently forms a posterior mandibular process. The greater part of the under-jaw is formed by the right and left dentaries, which in all recent birds are fused together in front. Supra-angular and coronoid splint-bones serve for the insertion of part of the temporal or masseter muscle. ”

“ The maxillary consists sometimes of one piece, sometimes of two or three. The principal membrane-bone of the mandible is the dentary (34) , to which is added the angular (36) and rarely a smaller one, the splenial or os operculare, which is situated at the inside of the articulary.
5. Cartilage-bones of the respiratory portion of the visceral skeleton of the skull.—With few exceptions all the ossifications of the hyoid and branchial arches, as described above (p. 58) , belong to this group. ”

“ 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. ”

“ Round the mouth is a small space, the walls of which are completed by the mandibles, and into this space the brushes are suddenly bent back, at the same time the mandibles and maxillae move forward to meet them. ”

“ C, Condyle of mandible; Col, columella cranii; F, frontal; I, interparietal or pineal foramen; I.A, Inner angle of mandible; J, jugal, shaded vertically; L, lacrymal; M, maxillary; N, nasal groove; Na, nasal bone; O, orbit; O1, preorbital fossa; P, parietal; Pf, postfrontal; Pm, premaxillary; Pr, prefrontal; Ptg, pterygoid; Q, quadrate; Qj, quadrato-jugal; Sq, squamosal, shaded obliquely; St, supratemporal bone.
{282}
The families cannot well be changed, and terms like super-families and super-orders are sometimes resorted to by those who do not like to look stern facts in the face. ”

“ The points to be specially noted in the maxilla are the thinness of the outer alveolar wall as compared with the inner, the prominence of the canine socket, and the cancellous character of the bone in the region of the third molar. In the mandible the outer alveolar border will be seen to be thinner than the inner, with the exception of that portion in the region of the{13}
Fig. ”

“ Mouth.—Maxillæ, with three large spines at the upper angle, and with the first step distinct, but narrow; mandibles with five teeth; in young specimens the inferior point ends in a single spine; sides of the supra-oral cavity very hairy; the membrane, forming the inner fold of the labrum, yellow and thickened in the form of a spoon. ”

“ The mandibles are straight for a greater part of their length, but the upper one is much hooked at the point, and very sharp, and the cutting edges of both mandibles are in all their length beset with short, but strong and sharp teeth inclining backward. ”

“ The actual piercing organs are the mandibles, while the upper lip or labrum forms a sucking tube. The maxillae are not piercing organs, and their function is to protect the mandibles and labrum and separate the hairs or feathers of the host. ”

“ The mouth is open and the mandibles long, slender, and straight. The eye is represented by a circlet which incloses a small conical pit intended to represent the iris, a striated and pointed crest springs from the back of the head and neck, and two lines extend from the eye, down the neck, to the base of the figure. ”

“ The jaws, (intermaxillaries and premandibles) are convex, rounded, and furnished with scale-like teeth on their margin and anterior surface. The jaws themselves resemble great teeth, and actually perform the office of teeth, being very thick and sharpened at the edges. ”

“ The maxillæ, or feeler-jaws, as they have not inappropriately been called, are placed below the mandibles, and correspond to them in being two triangular hooks, moving horizontally in opposition to each other. They are always smaller than the mandibles, usually of a more delicate texture, and instead of being toothed on their internal edge, are for the most part fringed with hairs or bristles. ”

“ The mandibles seem to shape themselves in accordance to the degree of intelligence; they become more finely modeled in proportion as the two social functions of speaking and smiling acquire a greater importance than the two individual functions of biting and masticating. ”

“ The head is not received into a cavity of the thorax, but is attached to it by a ligament, so flexible that the head can be almost turned round upon it. It is likewise capable of some extension, and the head has thereby considerable freedom of motion. The composite eyes are sometimes larger in the males than in the other sex. The stemmata are always three in number, commonly disposed in an equilateral triangle, but occasionally almost in a transverse line. In the organs of the mouth we can distinctly recognise mandibles, maxillæ, lingua, labrum, labium, and palpi ”

“ The lips, extending 15 to 20 feet in length, and 5 or 6 in height, and forming the cavity of the mouth, are attached to the under-jaw, and rise from the jaw-bones, at an angle of about 80 degrees, having the appearance, when viewed in front, of the letter U. The upper jaw, including the 'crown-bone,' or skull, is bent down at the extremity, so as to shut the front and upper parts of the cavity of the mouth, and is overlapped by the lips in a squamous manner at the sides. ”

“ 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. ”

“ Then I felt that he had seized my forehead just under the hair with the teeth of his lower jaw, and the flesh below my eyes with his upper jaw, and was closing his teeth. It was as if my face were being cut with knives. I struggled to get away, while he made haste to close his jaws like a dog gnawing. ”

“ The Mouth is formed by the intermaxillary and maxillary bones, or by the intermaxillary only in the upper jaw, and by the mandibulary bone in the lower. These bones are either bare or covered by integument, to which frequently labial folds or lips are added. As regards form, the mouth offers as many variations as the body itself, in accordance with the nature of the food, and the mode of feeding. ”

“ Lastly, with relation to their Use; some serve to support and carry the whole Body, as the Leg-Bones, and others are appointed to grind the Meat, as the Teeth; or else to form some Cavity, as the Skull-Bone, and those of the Ribs.
What are the Parts to be distinguished in the Bones?
They are the Body, the Ends, the Heads, the Neck, the Apophyses, the Epiphyses, the Condyli or Productions, the Cavities, the Supercilia or Lips, and the Ridges.
The Body is the greatest Part, and the middle of the Bone; the Ends are the two Extremities; the Heads are the great Protuberances at the Extremities ”

“ If at both ends, the whole chin projects outwards, the lower teeth are more prominent, and the muscles appear stretched. The patient being properly seated, and his head held by an assistant, the surgeon having wrapped his thumbs with linen cloths, is to put them into the patient’s mouth, while the fingers are applied externally. The jaw being firmly grasped, the chin is to be shaken, and then, at one and the same instant, the head is to be seized, the chin moved, the jaw forced into its place, and the mouth shut. ”

“ It is this relationship, 481the articulation of each bone with the other bones of the skull that is of primary importance to the Dental Surgeon.
The last bone that I shall mention to you this evening is the lower jaw, perhaps the most important of all. You will all soon be taught that it has a body, a symphysis, a ramus with its condyle, coronoid process and sigmoid notch, an alveolar process, and various tubercles, ridges, spines, grooves, and depressions. But beyond all such facts, be at pains to notice, gentlemen, how all these various parts differ in different specimens. ”

“ That the firm well-rounded chin, the resolute jaw and symmetrical cheeks, and the appearance of decision, vigor and alertness so necessary for either male or female beauty of expression, belong by right to every American man and woman; not to mention the fact that the "laughing pearls" of perfect teeth can be possessed by any one, and some one has sinned, either the man or his parents, if the denture is defective and the jaws ill-developed. ”

“ In connection with the skull, I may speak of the teeth—organs which have a peculiar classificatory value, and whose resemblances and differences of number, form, and succession, taken as a whole, are usually regarded as more trustworthy indicators of affinity than any others.
Man is provided with two sets of teeth—milk teeth and permanent teeth. The former consist of four incisors, or cutting-teeth; two canines, or eye-teeth; and four molars, or grinders, in each jaw, making twenty in all. ”

“ The angle of the jaw is produced backwards, and ends in an obtuse point, slightly bent upwards; a foramen, one-third less than the anterior one, leads from near the commencement of the dental canal, to the outer surface of the jaw, a little below and behind the last molar tooth ”

“ The bone is to be brought to its former shape by pressure of the fingers on the outside, and of the thumbs placed within the mouth on the corners of the teeth. Motion is prevented, and the parts are retained in their proper situation, by a wedge of cork or wood interposed on each side of the jaw, and grooved so as to receive the teeth both above and below. ”