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Second molar teeth to the left side, labial (A) and lateral (B) aspects.

Second Molar

Second molar teeth to the left side, labial (A) and lateral (B) aspects.

Longitudinal section (A) and transverse section (B) of a human molar tooth. Labels: c, cement; d, dentine; e, enamel; v, pulp cavity

Structure of a Molar

Longitudinal section (A) and transverse section (B) of a human molar tooth. Labels: c, cement; d, dentine;…

Triturating surfaces of molar teeth of right side. The upper margin of the figures corresponds to the labial surface.

Surface of Molar

Triturating surfaces of molar teeth of right side. The upper margin of the figures corresponds to the…

Temporary molar teeth (A, first; B, second) of left side. Triturating surfaces of crowns also shown.

Temporary Molar

Temporary molar teeth (A, first; B, second) of left side. Triturating surfaces of crowns also shown.

Vertical section of a molar tooth. Labels: a, enamel of the crown, the line of which indicate the arrangement of its columns; b, dentine; c,cement; d, pulp cavity.

Vertical Section of a Molar

Vertical section of a molar tooth. Labels: a, enamel of the crown, the line of which indicate the arrangement…

Vertical section of a molar tooth.

Vertical Section of a Molar

Vertical section of a molar tooth.

A monkey looking in to the distance upside down.

Monkey

A monkey looking in to the distance upside down.

Open mouth showing palate and tonsils. It also shows the two palatine arches, and the pharyngeal isthmus through which the nasopharynx above communicates with the oral portion of the pharynx below.

Mouth Showing Palate and Tonsils

Open mouth showing palate and tonsils. It also shows the two palatine arches, and the pharyngeal isthmus…

Nerves leading to the roots of the teeth.

Nerves Leading to Teeth Roots

Nerves leading to the roots of the teeth.

"Dental Branch of One of the Divisions of the Fifth Pair of Cranial Nerves, supplying the Lower Teeth. Branches from the motor root, distributed to various muscles, are also shown." — Blaisedell, 1904

Cranial Nerves

"Dental Branch of One of the Divisions of the Fifth Pair of Cranial Nerves, supplying the Lower Teeth.…

"Dental Branches of One of the Divisions of the Fifth Pair of Cranial Nerves, supply the Upper Teeth." — Blaisedell, 1904

Cranial Nerves

"Dental Branches of One of the Divisions of the Fifth Pair of Cranial Nerves, supply the Upper Teeth."…

A colt's nippers at five years of age (side view)

Nippers at five years

A colt's nippers at five years of age (side view)

Side view of a colt's nippers at seven years of age.

Nippers at seven years

Side view of a colt's nippers at seven years of age.

Side view of a colt's nippers at six years of age.

Nippers at six years

Side view of a colt's nippers at six years of age.

Side view of the nippers of an old horse.

Nippers of an Old Horse

Side view of the nippers of an old horse.

A colt's lower nippers at eight years.

Lower nippers at eight years

A colt's lower nippers at eight years.

Lower nippers of a colt at five years of age.

Lower nippers at five years

Lower nippers of a colt at five years of age.

The lower nippers of a colt at four years.

Lower nippers at four years

The lower nippers of a colt at four years.

Lower nippers of a colt at six years of age.

Lower nippers at six years

Lower nippers of a colt at six years of age.

The lower nippers of a colt at three years of age.

Lower nippers at three years

The lower nippers of a colt at three years of age.

The lower nippers of a colt two years old.

Lower nippers at two years

The lower nippers of a colt two years old.

Lower nippers of an old horse.

Lower Nippers of an Old Horse

Lower nippers of an old horse.

The palate and alveolar arch.

Palate

The palate and alveolar arch.

"Milkand permanent dentition of upper (I) and lower (II) jaw of the dog, with the symbols by which the different teeth are commonly designated. The third upper molar (m3) is the only tooh wanting in this animal to complete the typical heterodont mammalian dentition." —The Encyclopedia Britannica, 1903

Permanent Dentition

"Milkand permanent dentition of upper (I) and lower (II) jaw of the dog, with the symbols by which the…

"One half of the permanent set of teeth." — Ritchie, 1918

Half set of permanent teeth

"One half of the permanent set of teeth." — Ritchie, 1918

A premolar tooth of a cat.

Premolar of a Cat

A premolar tooth of a cat.

First premolar teeth of left side, labial (A) and lateral (B) aspects.

First Premolar

First premolar teeth of left side, labial (A) and lateral (B) aspects.

"A circular wheel, with teeth on the circumference, by which it can be moved or its motion stayed." — Williams, 1889

Ratchet-wheel

"A circular wheel, with teeth on the circumference, by which it can be moved or its motion stayed."…

"a. shank for fixing the implement to a bench; c. punch, hinged to a base b and e; and pressed upward by springs; h. screw-support for the back of the blade; d. gauge which may be adjusted for different-sized teeth. The blade is moved along to bring alternate teeth under the punch, which his struck with a hammer." —Whitney, 1889

Saw Set for a Work Bench

"a. shank for fixing the implement to a bench; c. punch, hinged to a base b and e; and pressed upward…

A saw-set is an "instrument used to wrest or turn the teeth of saws alternately to the right left so that they may make a kerf somewhat wider than the thickness of the blade. Also called saw-wrest. b. anvil used for setting saws in saw-factories, the setting being performed by blows of the peculiarly shaped hammer; a. Every second tooth is set in one direction, and, the saw-blade being turned over, the intervening teeth are set in the reverse direction; c and d are notched levers by which in ordinary setting the alternate teeth are set in opposite directions." —Whitney, 1889

Collection of Saw-Sets

A saw-set is an "instrument used to wrest or turn the teeth of saws alternately to the right left so…

<i>Pristis pectinatus</i>. "1. An elasmobranchiate or selachian fish of the family <i>Pristidae</i>, having the snout prolonged into a flat saw or serra beset on each side with horizontal teeth pointing sidewise." &mdash;Whitney, 1889

Sawfish, Side View

Pristis pectinatus. "1. An elasmobranchiate or selachian fish of the family Pristidae, having the snout…

<i>Pristis pectinatus</i>. "1. An elasmobranchiate or selachian fish of the family <i>Pristidae</i>, having the snout prolonged into a flat saw or serra beset on each side with horizontal teeth pointing sidewise." &mdash;Whitney, 1889

Sawfish, View from Underneath

Pristis pectinatus. "1. An elasmobranchiate or selachian fish of the family Pristidae, having the snout…

This illustration includes numerous types of saws: a. Circular saw (right-hand and left-hand saws have the teeth running opposite directions); b. section of circular saw showing flange at c; d. concave saw; e. circular saw with inserted teeth; f. mill-saw; g. ice-saw; h. cross-cut saw; i. band-saw; j. rip-saw; k. hand-saw; l. panel-saw; m. pruning-saw; n. whip-saw; o. wood-saw; p. keyhole or compass-saw; q. back-saw; r. bow-back butchers' saw.

Collection of Saws

This illustration includes numerous types of saws: a. Circular saw (right-hand and left-hand saws have…

Screw-and-Worm gearing is a type of gearing in which the velocity ratio is independent of the radii of the pitch surfaces, the teeth of the wheels essentially being portions of screw surfaces. This kind of gearing is used in speed-reducing arrangements.

Screw-and-Worm Gearing

Screw-and-Worm gearing is a type of gearing in which the velocity ratio is independent of the radii…

The skull of a serpent with visible teeth.

Serpent Skull

The skull of a serpent with visible teeth.

"A, Palate process of upper jawbone; B, zygoma, forming zygomatic arch; C, condyle, for forming articulation with atlas; D, foramen magnum; E, occipital bone" &mdash; Blaisedell, 1904

Base of skull

"A, Palate process of upper jawbone; B, zygoma, forming zygomatic arch; C, condyle, for forming articulation…

The base of the skull. "The lower jaw has been removed. At the lower part of the figure is the hard palate forming the roof of the mouth and surrounded by the upper set of teeth. Above this are the paired opening of the posterior nares, and a short way above the middle of the figure is the large median foramen magnum, with the bony convexities (or occipital condyles) which articular with the atlas, on its sides. It will be seen that the part of the skull behind the occipital condyles is about equal in size to that in front of them; in an ape the portion in front of the occipital condyles would be much larger than that behind them." &mdash;Newell, 1900

Base of the Skull

The base of the skull. "The lower jaw has been removed. At the lower part of the figure is the hard…

"...a variety of calcite, crystallizing in scalenohedral forms; so named from a fancied resemblance of its crystals to canine teeth." —Whitney, 1889

Dogtooth Spar

"...a variety of calcite, crystallizing in scalenohedral forms; so named from a fancied resemblance…

"A wheel having teeth projecting radially from the circumference." &mdash; Williams, 1889

Spur-wheel

"A wheel having teeth projecting radially from the circumference." — Williams, 1889

"System of Wheels.&mdash;As the wheel and axle is only a modification of the simple lever, so a system of wheels acting on each other, and transmitting the power to the resistance, is only another form of the compound lever. The first wheel a, by means of the teeth, or cogs, around its axle, moved the second wheel, b, with a force equal to that of a lever, the long arm of which extends from the center to the circumference of the wheel, where the power p is suspended, and the short arm from the same center to the ends of the cogs. The dotted line c, passing through the center of the wheel a, shows the position of the lever, as the wheel now stands." &mdash;Comstock, 1850

System of Wheels

"System of Wheels.—As the wheel and axle is only a modification of the simple lever, so a system…

The series of small bones attached to the jaws of animals, or human beings, which serve the purpose of taking and chewing food.

Teeth

The series of small bones attached to the jaws of animals, or human beings, which serve the purpose…

The hard, bony structures situated in the mouth or near the entrance to the pharynx of vertebrates, which are partially exposed when developed and employed for seizing and chewing food.

Teeth

The hard, bony structures situated in the mouth or near the entrance to the pharynx of vertebrates,…

Full permanent set of teeth, seen in front.

Teeth

Full permanent set of teeth, seen in front.

To show the relation of the upper to the lower teeth when the mouth is closed. The manner in which a tooth of one row usually strikes against two teeth of the opposite row, and the resulting interlocking of the teeth, is to be noted.

Teeth

To show the relation of the upper to the lower teeth when the mouth is closed. The manner in which a…

Front and side views of the teeth and jaws.

Teeth and Jaws

Front and side views of the teeth and jaws.

Teeth of a carnivorous animal that lives on flesh alone. The front teeth are designed for tearing, while the back teeth have sharp edges for cutting.

Teeth of a Carnivorous Animal

Teeth of a carnivorous animal that lives on flesh alone. The front teeth are designed for tearing, while…

Temporary teeth in a child aged about 4 years. The permanent teeth are seen in the process of formation in their alveoli or sockets.

Teeth of a Child

Temporary teeth in a child aged about 4 years. The permanent teeth are seen in the process of formation…

Teeth of a frugivore (fruit-eating animal). Animals that live on soft fruits do not need such grinders as grass-eating animals do, instead they have rounded teeth which serve to crush their food.

Teeth of a Frugivore

Teeth of a frugivore (fruit-eating animal). Animals that live on soft fruits do not need such grinders…

Teeth of an herbivore, showing the rough surface of some of these teeth. Herbivores have no tearing teeth. Instead they have two kinds of teeth, cutting teeth in the front and grinding teeth in the back. This figure shows a peculiar arrangement of the enamel, which admirably fits them to grind up the fibers of the grass in the back grinding teeth of an herbivore. The enamel is not only on the outside as it is in human teeth, rather there are ridges on it standing up in the middle of each tooth.

Teeth of an Herbivore

Teeth of an herbivore, showing the rough surface of some of these teeth. Herbivores have no tearing…

The image on the left are the teeth of a carnivora or flesh-eating animal. The teeth on the right belong t a insectivora or insect-eating animal. Notice the projecting jaw, the wide mouth, and sharp teeth of the carnivore animal in contrast with the elongated, tapering muzzle and cone-pointed molars of the insectivorous animal.

Comparing Teeth of Carnivora and Insectivora Animals

The image on the left are the teeth of a carnivora or flesh-eating animal. The teeth on the right belong…

1. Dentition (teeth) of man. 2. Dentition of hyena. 3. Dentition of pig. 4. Dentition of Patagonian cavy (type of rodent). 5. Section of skull of Indian elephant, showing dentition of right side. 6. Crown of upper molar of horse, showing enamal folds. 7. Grinding surface of molar of African elephant, with enamal folds. 8. Single tooth of blue shark. 9. Longitudinal section of human tooth. 1. Incisors (human); C, canines; P, premolars; M, molars. a, enamel; b, dentine; c, cement (crusta petrosa); d, pulp cavity.

Teeth of Man and Several Animal Species

1. Dentition (teeth) of man. 2. Dentition of hyena. 3. Dentition of pig. 4. Dentition of Patagonian…

Half of the teeth of the upper jaw. <em>a,a,</em> are the two front cutting teeth. <em>d,d,d</em> are the three large back teeth. c,c are two smaller grinders. At <em>b</em> is what is commonly called an "eye-tooth."

Teeth of the Upper Jaw

Half of the teeth of the upper jaw. a,a, are the two front cutting teeth. d,d,d are…

The adult teeth. Labels: 1, 2, The cutting teeth (incisors). 3, Eyetooth (cuspid). 4,5, Small grinders (bicuspids). 6, 7, 8, Grinders (molars). 9, 9, Neck of the tooth.

The Adult Teeth

The adult teeth. Labels: 1, 2, The cutting teeth (incisors). 3, Eyetooth (cuspid). 4,5, Small grinders…

The deciduous and permanent teeth, shown as they are placed in the jaw with portions of bone removed to reveal the roots.

The Deciduous and Permanent Teeth

The deciduous and permanent teeth, shown as they are placed in the jaw with portions of bone removed…

The first step in the development of teeth consists in a downward growth from the Rete Malpighi or the deeper layer of stratified epithelium of the mucous membrane of the mouth, which first becomes thickened in the neighborhood of the maxillae now in the course of formation. This development is shown in a section of the upper jaw of a fetal sheep. A- 1, common enamel germ dipping down into the mucous membrane; 2, palantine process of jaw; 3, Reta Malpighi. B- Section similar to A, but passing through one of the special enamel germs here becoming flask-shaped; c, d, epithelium of mouth; f, neck; f', body of special enamel organ; p, papilla; s, dental sac forming; f p, the enamel germ of permanent tooth; m, bone of jaw; v, vessel cut across.

Development of Teeth

The first step in the development of teeth consists in a downward growth from the Rete Malpighi or the…

Well formed jaws, from which the alveolar plate has been removed to expose the developing permanent teeth in their crypt in the jaws.

Development of Permanent Teeth

Well formed jaws, from which the alveolar plate has been removed to expose the developing permanent…

A horse's mouth at eight years old.

Eight Year Old Horse Teeth

A horse's mouth at eight years old.

The teeth of a 6 and a half year old child. Label: I, the incisors; O, the canine; M, the molars; the last molar is the first permanent teeth; F, sacs of the permanent incisors; C, of the canine; B, of the bicuspids; N, of the second molar; the sac of the third molar is empty.

Emergence of Adult Teeth

The teeth of a 6 and a half year old child. Label: I, the incisors; O, the canine; M, the molars; the…

"A Tooth is one of the hard bodies of the mouth, attached to the skeleton, but not forming part of it and developed from the dermis or true skin. True teeth consist of one, two, or more tissues differing in their chemical composition and in their microscopical appearances. Dentine, which forms the body of the tooth, and 'cement,' which forms its outer crust, are always present, the third tissue, the 'enamel,' when present, being situated between the dentine and cement. The incisors, or cutting teeth, are situated in front. In men there are two of these incisors in each side of each jaw. The permanent incisors, molars, and premolars are preceded by a set of deciduous or milk teeth, which are lost before maturity, and replaced by the permanent ones. The canines come next to the incisors. In man there is one canine tooth in each half-jaw. The premolars (known also as bicuspids and false molars) come next in order to the canines. In man there are two premolars in each half-jaw. The true molars (or multicuspids) are placed most posteriorly. In man there are three molars in each half-jaw, the posterior one being termed the wisdom tooth. The figures [in the illustration] refer to months after birth."&mdash;(Charles Leonard-Stuart, 1911)

First Teeth

"A Tooth is one of the hard bodies of the mouth, attached to the skeleton, but not forming part of it…

A horse's mouth at five years old.

Five Year Old Horse Teeth

A horse's mouth at five years old.