The Vertebrate Skeleton

Name: The Vertebrate Skeleton
Author: Reynolds, Sidney H. (Sidney Hugh)

Reynolds, Sidney H. (Sidney Hugh)

Skeleton

Lying immediately ventral to the nasals, and on each side of the
perpendicular mesethmoid, are the =ethmoid= or =turbinal= bones,
which have a curious character, being formed of a number of delicate
plates intimately folded on one another. The posterior pair of these
bones, the =ethmo-turbinals= (fig. 72, 10), are the larger, and form a
mass of intricately folded lamellae attached behind to the cribriform
plate, and passing laterally into two thin plates of bone, which abut
on the maxillae. The uppermost lamella of each ethmo-turbinal is larger
than the others and more distinct. It is sometimes distinguished as
the =naso-turbinal=, and forms an imperfect lower boundary to a canal,
which is bounded above by the nasals. In front of and somewhat below
the ethmo-turbinals, lie another pair of bones of similar character,
the =maxillo-turbinals= (fig. 72, 11).

The last bone to be mentioned in connection with the olfactory
capsules is a membrane bone, the _vomer_ (fig. 72, 9). This is a
slender vertically-placed bone, whose anterior part lies between the
maxillo-turbinals, while behind it extends beyond the mesethmoid, so
as to underlie the anterior part of the presphenoid. The anterior part
of the vomer forms a kind of trough, while further back in the region
of the ethmo-turbinals it sends out a pair of strong lateral plates,
each of which, passing below the ethmo-turbinal, joins the side wall
of the nasal cavity, and forms a partition dividing the nasal cavity
into a lower =narial passage= and an upper =olfactory chamber=.


THE JAWS.

In the embryo both upper and lower jaws are formed of cartilaginous
bars, but in the adult not only has the cartilage entirely
disappeared, but even cartilage bone is absent, the jaws being formed
of membrane bone.


3. THE UPPER JAW.

[Illustration FIG. 75. VENTRAL VIEW OF THE CRANIUM OF A DOG (_Canis
familiaris_) × 3/5. (Camb. Mus.)

    1. supra-occipital.
    2. foramen magnum.
    3. occipital condyle.
    4. tympanic bulla.
    5. basi-occipital.
    6. basisphenoid.
    7. external auditory meatus.
    8. glenoid fossa.
    9. foramen lacerum medium and anterior opening of carotid canal.
    10. postglenoid foramen.
    11. alisphenoid.
    12. presphenoid.
    13. vomer.
    14. jugal.
    15. pterygoid.
    16. palatal process of palatine.
    17. maxillae (palatal portion).
    18. posterior palatine foramina.
    19. anterior palatine foramen.
    20. premaxillae.
    21. alisphenoid canal.
    22. Eustachian foramen.
    23. postglenoid process of squamosal.
    II. optic foramen.
    III, IV, V{1}, VI. foramen lacerum anterius.
    V{2}. foramen rotundum.
    V{3}. foramen ovale.
    VII. stylomastoid foramen.
    IX, X, XI. foramen lacerum posterius.
    XII. condylar foramen.
    _i_ 2. second incisor.
    _c._ canine.
    _pm_ 1, _pm_ 4. first and fourth premolars.
    _m_ 1. first molar.]

Public-domain text, read in full here on John Shaqi.

Opening the text

The Vertebrate SkeletonReynolds, Sidney H. (Sidney Hugh)

Science

The Vertebrate Skeleton

Reynolds, Sidney H. (Sidney Hugh)

Skeleton

Lying immediately ventral to the nasals, and on each side of the
perpendicular mesethmoid, are the =ethmoid= or =turbinal= bones,
which have a curious character, being formed of a number of delicate
plates intimately folded on one another. The posterior pair of these
bones, the =ethmo-turbinals= (fig. 72, 10), are the larger, and form a
mass of intricately folded lamellae attached behind to the cribriform
plate, and passing laterally into two thin plates of bone, which abut
on the maxillae. The uppermost lamella of each ethmo-turbinal is larger
than the others and more distinct. It is sometimes distinguished as
the =naso-turbinal=, and forms an imperfect lower boundary to a canal,
which is bounded above by the nasals. In front of and somewhat below
the ethmo-turbinals, lie another pair of bones of similar character,
the =maxillo-turbinals= (fig. 72, 11).

The last bone to be mentioned in connection with the olfactory
capsules is a membrane bone, the _vomer_ (fig. 72, 9). This is a
slender vertically-placed bone, whose anterior part lies between the
maxillo-turbinals, while behind it extends beyond the mesethmoid, so
as to underlie the anterior part of the presphenoid. The anterior part
of the vomer forms a kind of trough, while further back in the region
of the ethmo-turbinals it sends out a pair of strong lateral plates,
each of which, passing below the ethmo-turbinal, joins the side wall
of the nasal cavity, and forms a partition dividing the nasal cavity
into a lower =narial passage= and an upper =olfactory chamber=.


THE JAWS.

In the embryo both upper and lower jaws are formed of cartilaginous
bars, but in the adult not only has the cartilage entirely
disappeared, but even cartilage bone is absent, the jaws being formed
of membrane bone.


3. THE UPPER JAW.

[Illustration FIG. 75. VENTRAL VIEW OF THE CRANIUM OF A DOG (_Canis
familiaris_) × 3/5. (Camb. Mus.)

    1. supra-occipital.
    2. foramen magnum.
    3. occipital condyle.
    4. tympanic bulla.
    5. basi-occipital.
    6. basisphenoid.
    7. external auditory meatus.
    8. glenoid fossa.
    9. foramen lacerum medium and anterior opening of carotid canal.
    10. postglenoid foramen.
    11. alisphenoid.
    12. presphenoid.
    13. vomer.
    14. jugal.
    15. pterygoid.
    16. palatal process of palatine.
    17. maxillae (palatal portion).
    18. posterior palatine foramina.
    19. anterior palatine foramen.
    20. premaxillae.
    21. alisphenoid canal.
    22. Eustachian foramen.
    23. postglenoid process of squamosal.
    II. optic foramen.
    III, IV, V{1}, VI. foramen lacerum anterius.
    V{2}. foramen rotundum.
    V{3}. foramen ovale.
    VII. stylomastoid foramen.
    IX, X, XI. foramen lacerum posterius.
    XII. condylar foramen.
    _i_ 2. second incisor.
    _c._ canine.
    _pm_ 1, _pm_ 4. first and fourth premolars.
    _m_ 1. first molar.]

Public-domain text, read in full here on John Shaqi.

The Vertebrate Skeleton

The Vertebrate Skeleton

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