Hyoid bone

“ The thyroid bone has an anterior curved prolongation, which projects forwards, and from the extremity of which comes the elastic ligament by which it is connected with the hyoid bone. The œsophagus, a, b, is 15 inches long, measured to the commencement of the proventriculus, extremely dilated, its diameter 2 1/2 inches at the top, contracting to 2 inches as it enters the thorax, its narrowest part 1 inch 4 twelfths; its transverse muscular fibres moderately strong. The proventriculus, c, d, is excessively large, 3 1/2 inches long, its greatest diameter 2 1/4 inches. ”

“ If a person puts a cord around the neck between the hyoid bone and the chin, he can draw it tight at the back or side, without the respiration being sensibly interfered with, and can for a long time continue to inspire and expire naturally enough, because in this situation compression is not made on any part of the air-passages. ”

“ It is produced by a drum-shaped expansion of the larynx. The hyoid bone, which in man is but slightly developed, is in these monkeys very large. It gives support to the tongue, being attached to the muscles of the neck. ”

“ It will be seen, on reading the subsections devoted to embry- ology and comparative anatomy^ that in man the maxilla, palate, internal pterygoid plate, malar and tympanic bones as well as the ear ossicles, mandible, hyoid bone and thyroid cartilage are developed in connexion with this visceral skeleton. Of these the ear ossicles are described in the article Ear, the thyroid cartilage in that on the Respiratory System, while the other bones, with the exception of the hyoid, are treated under the head of Skull. It therefore only remains to describe here the hyoid bone of man. ”

“ It is long and slender, with a horny point, and is capable of being protruded for more than twice the length of the head, in consequence of the extreme elongation of the two branches of the flexible or hyoid bone, as it is termed, which supports the tongue, curling round at the back of the head, dividing and passing over each eye, at the forehead, where the branches reunite and extend to the base of the upper mandible. ”

“ The hyoid arch has a number of ossifications in it and is closely connected with the mandibular arch.
The hyomandibular (fig. 11, 24) is a large bone which articulates with a shallow groove lined by cartilage and formed partly in the pterotic, partly in front of it. The hyomandibular is overlapped in front by the meta-pterygoid, while below it tapers and is succeeded by a small area of unossified cartilage followed by the forwardly-directed symplectic which fits into a groove in the quadrate. ”

“ The outer fibres run in fasciculi from the lower and inner edge of the mandible; those from its base pass downwards, those arising more anteriorly pass gradually 98 more forwards, and spreading out, reach the middle line of the pouch. The inner fibres have the same origin, and pass in a contrary direction, backwards and inwards. From the hyoid bone to the junction of the two crura of the mandible, which takes place almost at the very tip, there extends a thin band of longitudinal muscular fibres, in the centre of which is a cord of elastic tissue. ”

“ She has a bearish look, and it is evident that the colours of both sexes are admirably adapted to hide them when crawling amongst rocks, or hiding away in holes and under ledges of stone. All have a wild, grunting bark, almost approaching a roar; and they possess laryngeal pouches or air sacs, which pass amongst the muscles of the neck and reach even into the armpits. The pouch communicates by one opening into the membrane above the larynx, and between its cartilage and the so called hyoid bone at the base of the tongue, and they, therefore, resemble those of the Semnopitheci. ”

“ It arises, in the horse, from the cervical border of the scapula, where it blends with the aponeurosis that envelops the subscapularis muscle, but in the pig and the ox it arises from the deep surface of the mastoido-humeral muscle. It is directed obliquely upwards and inwards, becoming superficial at the internal border of the sterno-mastoid, and is inserted into the hyoid bone. ”

“ The mesotympanic or symplectic (31) appears as a styliform prolongation of the lower part of the hyomandibular; is entirely cartilaginous in the young, but nearly entirely ossified in the adult. The position of this bone is noteworthy, because, directly inwards of its cartilaginous junction with the hyomandibular, there is situated the uppermost piece of the hyoid arch, the stylo-hyal. The next bone of the series is the pretympanic or metapterygoid (27) , a flat bone forming a bridge towards the pterygoid, and not rarely absent in the teleosteous sub-class. ”

“ The hyoid arch is suspended by a slender styliform bone, the stylohyal (29) , from the hyomandibulars; it consists of three segments, the epihyal (37) , ceratohyal (38) , which is the longest and strongest piece, and the basihyal, which is formed by two juxtaposed pieces (39, 40) . ”

“ The angle of the lower jaw is very large and massive, and their chief characteristic is the conspicuous thickening of the throat, owing to the great enlargement of the hyoid bones—which are widely inflated and cavernous—to form the curious vocal organ which the males of these animals possess, and by which their voice can be so augmented as to be heard at a distance of several miles. ”

“ A similar arrangement of external protection takes place in this genus over the bones of the head; the cartilaginous jaws receive their osseous dermal covering, and, with these, the hyoid bones, the opercules, and the cranium. And it is in these dermal plates, which covered an interior skull, of which, save in one genus,—the Dipterus,—not a vestige remains in any of the Old Red fishes thus protected, that we first trace what [70] seem to be the homologues of the cranial bones of the osseous fishes,—at least their homologues so far as the cuticular can represent the internal. ”

“ Sterno-hyoideus. Location.—Inferior to the hyoid apparatus.
Origin.—From the outer anterior surface of the thyroid bone of the superior larynx.
Insertion.—To the anterior part of the basi-hyal.
Shape.—At first broad and rather fleshy, becomes contracted and somewhat tendinous.
Relations.—Inferior to the hyoid apparatus and superior larynx.
Action.—When the larynx is fixed, acting alone deflects the tongue laterally; acting with its fellow, depresses the tongue. If the base of the tongue is fixed the two pull the larynx forward. Hence muscles of deglutition. ”

“ The hyoid apparatus is very large, with enormous anterior and posterior horns. The head and neck are as long as or even longer than the carapace, which is covered with thick, lumpy shields. The skin of the thick neck, of the sides and under parts of the head, is produced into many soft arborescent excrescences or fimbriae, those of the chin and throat and the large ear-flaps being movable at will, and probably used to attract fishes and other prey. ”

“ The hyoid branch separates from the hyomandibular trunk at about the same level as the preceding nerves, and then passes, deep in the tissues, around the angle of the jaw to the ventral side where it is distributed to the superficial constrictor muscles. Several nerves pass from the hyomandibular trunk and the hyoid branch to the dorsal superficial constrictors. ”

“ The palato-pterygo-quadrate and Meckel's cartilages together form the primitive upper and lower jaws, and support the teeth. The hyoid arch also consists of a dorsal and a ventral half on each side. The dorsal half or hyomandibular element articulates above with the periotic capsule. The ventral portion, or cerato-hyal, passes downwards and is connected with its fellow by a median copula or basi-hyal cartilage situated in the floor of the oral cavity. A series of simple cartilaginous rays (branchial rays) are attached to the hinder margins of the hyomandibular and cerato-hyal elements. ”

“ In most species the hyoids are simple, consisting of a chain of slender, long, cylindrical bones connecting the basi-hyoid with the skull, while the pharynx is short, and the larynx shallow with feebly developed vocal cords, and guarded by a short pointed epiglottis. In the African epauletted bats, Epomophorus, the pharynx is long and capacious, the aperture of the larynx far removed from the fauces, and, opposite to it, opens a canal, leading from the nasal chambers, and extending along the back of the pharynx ”

“ As development proceeds, the increase in size of the quadrate, does not keep pace with that of the skull structures. It loses its connection with the palato-pterygoid, and apparently ossifies as a small ossicle-- the incus of the middle ear. A small nodule of cartilage, cut off from the proximal end of Meckel's cartilage, becomes the malleus. The stapes would appear to be derived from the hyoid arch. Hence these small bones seem to be the relics of the discarded jaw suspensorium of the frog utilized in a new function. ”

“ The mandible is rather short and broad, and the angle formed by the meeting of the two rami is more obtuse than in most mammals. The coronoid process is fairly well developed, and the angle is more or less rounded. In most Primates the condyle is considerably widened, but this is not the case in Man. In Mycetes the mandible is very large, its ascending portions being specially developed. The hyoid of Primates is [485] remarkable for the large expanded basi-hyal, which is generally concave above and convex below. The anterior cornu is never well ossified, but the thyro-hyal is always strong. ”

“ The pre-frontals (2) , also small, occupy the anterior margin of the orbit. A pair of small tubiform bones (20) , the turbinals, occupy the foremost part of the snout, in front of [58] the frontals, and are separated from each other by intervening cartilage.
After removal of the gill-cover and mandibulary suspensorium, the hyoid arch, which encloses the branchial apparatus, and farther behind, the humeral arch are laid open to view (Fig. 25) . These parts can be readily separated from the cranium proper. ”

“ 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 ”

“ These animals form a group of abnormal worm-like Amphibia having an exoskeleton in the form of subcutaneous scales arranged in rings. The vertebrae are biconcave and are very numerous; very few however belong to the tail. The skull has a complete secondary bony roof, the mandible bears teeth and has an enormous backward projection of the angular. The hyoid arch has very slender cornua and no distinct body, it is attached neither to the cranium nor to the suspensorium. The ribs are very long and there are no limbs or limb girdles. ”

“ The left parotic process is well displayed, and is proportionally large, being half an inch long and 0⋅3 inch wide. The base of the skull exhibits the injured basioccipital region, and the more perfect basisphenoid, which possesses two strong, divergent, basipterygoid processes. Against the outer ends of these the strong pterygoid bones abut. These are not at all unlike the corresponding bones in an Iguana. The central part, or body, of the bone is very strong; and it sends backwards and outwards a deep, laterally compressed plate, which abuts against the inner side of the quadrate bone. ”

“ The hyoid consists of three pieces, of which the posterior bears a broad branchiostegal in Polyodon.
In the scapulary arch the primordial cartilaginous elements scarcely differ from those of the Dipnoi. The membrane-bones are much expanded, and offer a continuous series suspended from the skull. Their division in the median ventral line is complete. ”

“ In this section we have therefore to deal chiefly with the white blood corpuscles and their connection with the bone-marrow. In man as in a large number of animals (for example the monkey, guinea-pig, rabbit, pigeon and so forth) the bone-marrow exhibits the peculiarity that the cells it produces bear a specific granulation, in sharp contrast to the lymphatic glandular system, which contains elements free from granules, in the whole animal series. ”

“ A small opening soon appeared where the four bones meet below in the Theromorpha (Figs. 114 c, 117) , and increased in size, till, in most reptiles, since Triassic times at least, this pubo-ischiatic opening extended on each side nearly to the acetabulum, leaving only a narrow connection between the pubis and ischium (Fig. 118) . Later, the symphysial ends of the pubis and ischium became connected in many by ligaments, or cartilage (Fig. 120) , and later in some by bone, producing a false obturator or thyroid vacuity on each side. ”

“ But the principal duty of the hyenas is to clear away bones, and very thoroughly they do it.
Their jaws and teeth are immensely strong. A hyena will seize the thigh-bone of an ox, and crush it up into splinters as easily as a dog will crush a chicken-bone. And when a lion or a tiger kills a victim, he always leaves a great part of the carcass lying on the ground. Some of it he has no time to eat because the jackals come and steal it while he is fast asleep after the big meal which he always takes as soon as he has killed his victim. ”