bones. 3, Orbital gland. 4, Ophthalmic division of the fifth pair of
cranial nerves. 5, Section through the cerebrum. 6, Section through
the skull showing the air spaces. 7, Section through the comb. 8,
Anterior portion of the upper beak. 9, Edge of the hard palate.
_B._ The intrinsic muscles of the eyeball. 1, Superior rectus. 2,
Internal rectus. 3, Inferior rectus. 4, External rectus. 5, Superior
oblique. 6, Inferior oblique. 7, Quadratus. 8, Pyramidalis. 9, Optic
nerve. 10, Edge of membrana nictitans.
_C._ Posterior part of the eye showing at the inferior portion of the
ball the pyramidalis muscle at 1, and at 2, the quadratus. 3, Optic
nerve.
_D._ Inner view of the posterior part of the vitreous chamber. 1,
Sclerotic coat. 2, Choroid coat. 3, Retina. 4, Pecten.
_E._ Longitudinal section through the eye of a hen. 1, Cornea. 2,
Anterior chamber. 3, Scleral ring. 4, Crystalline lense. 5, Iris. 6,
Retina. 7, Sclerotic. 8, Choroid. 9, Pecten. 10, Optic nerve. 11,
Vitreous chamber.
_F._ An edge view of the crystalline lense of a hen showing it to be
asymmetrical biconvex. 1, The anterior side. 2, The posterior side.
_G._ The upper section through the anterior portion of the anterior
turbinated bone showing one complete circle and the lower a section
through the middle turbinated showing one and one-half turns.
]
_Origin._—From the orbital septum just back of the inner canthus, the
fibers passing backward and forward.
_Insertion._—Into the sclera, anterior to the sclerotic plates.
_Shape._—Small, thin, fan-shaped.
_Relations._—With the eyeball, superiorly; at its extremities with the
superior rectus, interiorly.
_Action._—Rotates the eyeball.
=Obliquus Inferior= (Fig. 26, No. _B_, 6). (Synonym.—Obliquus
ventralis.)
_Location._—Inferior to the eyeball.
_Origin._—From the interorbital septum near the inner canthus of the
eye.
_Insertion._—By a broad expansion to the inferior portion of the
eyeball.
_Shape._—Tendinous at its insertions; fan-shaped as it passes downward
and outward.
_Relations._—Internally, with the eyeball; and externally, with the bony
orbital wall, with the inferior rectus muscle, inferiorly.
_Action._—Aids in rotating the eye; opposes the obliquus superior.
=Rectus Superior= (Fig. 26, No. _B_, 1). (Synonym.—Rectus dorsalis.)
_Location._—Superior to the eyeball.
_Origin._—Along the supero-posterior border of the optic foramen.
_Insertion._—To the sclera just within the margin of the bony circle of
the eye.
_Shape._—Flat, thin.
_Relations._—Internally, with the obliquus superior; superiorly, with
the bony wall of the orbit.
_Action._—To pull the eyeball upward.
=Rectus Inferior= (Fig. 26, No. _B_, 3). (Synonym.—Rectus ventralis.)
_Location._—Inferior to the eyeball.
_Origin._—From the inferior border of the optic foramen.
_Insertion._—To the lower portion of the eyeball within the margin of
the bony circle of the eye.
_Shape._—Thin, fan-shaped.
_Relations._—Superiorly, with the eyeball; inferiorly, with the bony
wall of the orbit.
_Action._—Pulls the eyeball downward.
=Rectus Externus= (Fig. 26, No. _B_, 4). (Synonym.—Rectus lateralis.)
_Location._—External to the eyeball.
_Origin._—By two heads infero-laterally to the optic foramen.
_Insertion._—To the postero-external side of the eyeball.
_Shape._—Short, fan-shaped.
_Relations._—Internally, with the eyeball; externally, with the bony
wall of the orbit.
_Action._—Pulls the eyeball outward.
=Rectus Internus= (Fig. 26, No. _B_, 2). (Synonym.—Rectus medialis.)
_Location._—Inner side of the eyeball.
_Origin._—From the supero-anterior border of the optic foramen.
_Insertion._—To the sclera on the anterior portion of the eyeball.
_Shape._—Thin, fan-shaped.
_Relations._—Internally, with the eyeball and with the pyramidalis;
externally, with the bony wall of the orbit.
_Action._—Pulls the eyeball inward.
THE MUSCLES OF THE EAR
Circumconcha
Tensor tympani
=Circumconcha= (Fig. 7, No. 32). _Location._—Surrounds the external ear.
_Origin and Insertion._—The circumconcha, surrounding the periphery of
the ear, is adherent to the skull and loosely to the skin, and is
attached to the outer terminus of the supra-occipital crest.
_Relations._—Internally, with the skull; externally, with the skin.
_Action._—Relaxes the tympanum.
=Tensor Tympani= (Fig. 7, No. 31). _Location._—External to the quadrate
and to the external auditory meatus.
_Origin and Insertion._—From the surface of the quadrate and the inner
end of the quadrato-jugal to the inner surface of the tympanum.
_Shape._—A few fibers.
_Relations._—Internally, with the quadrate and the quadrato-jugal;
externally, the integumental duplicature.
_Action._—Tenses the tympanum.
FUNCTIONS OF MUSCLES
To cause the feathers on the top of the head to lie flat:
Dermo-frontalis.
To raise the feathers along the superior part of the neck and along the
dorsal region:
Dermo-dorsalis.
To tense the patagial region:
Dermo-tensor patagii,
Dermo-temporalis.
To cause the feathers to lie close to the body:
Dermo-humeralis,
Dermo-pectoralis.
To tense the lateral cervical integument:
Dermo-temporalis.
To support the lingual apparatus and superior larynx:
Platysma myoides.
To manipulate the feathers and skin of the inferior part of the neck:
Cleido-trachealis.
To control the skin in the shoulder region:
Dermo-spinalis.
To cause the feathers of the back to lie close to the skin:
Dermo-iliacus.
To depress the humeral region:
Dermo-ulnaris.
To close the jaw:
Temporalis,
Pterygoideus internus,
Pterygoideus externus,
Masseter.
To open the jaw:
Biventer maxilla,
Entotympanic.
To raise the trachea and hyoid apparatus:
Digastricus.
To elevate the tongue:
Mylo-hyoideus.
To pull the tongue to one side:
Singly[5]—
Cerato-hyoideus,
Stylo-hyoideus.
Alone when the larynx is fixed—
Sterno-hyoideus.
Those which protrude the tongue from the mouth:
Together—
Cerato-hyoideus,
Genio-hyoideus.
To aid in deglutition:
When the base of the tongue is fixed—
Sterno-hyoideus.
To depress the tongue:
Together—
Sterno-hyoideus.
To depress the tip of the tongue and elevate the base:
Depressor glottis.
To elevate the hyoid arches:
Cerato-glossus.
To extend the head:
Complexus,
Rectus capitis anticus minor.
To flex the head upon the neck:
Flexor capitis inferior.
To extend the head on the neck and elevate the neck:
Biventer cervicis.
To raise the neck upward:
Longus colli posticus.
To flex each vertebra on the preceding or succeeding laterally:
Obliquus colli,
Intertransversales.
To pull the neck downward:
Longus colli anterior.
To pull the head downward:
Together—
Rectus capitis lateralis,
Trachelo-mastoideus.
To pull the head downward and to one side:
Singly—
Rectus capitis lateralis,
Trachelo-mastoideus.
To approximate the spinous processes of the vertebræ:
Interspinales.
To approximate the vertebræ in a supero-lateral direction:
Interarticulares.
To flex the vertebræ supero-laterally:
Obliquo-transversales.
To extend the neck:
Together when the first rib is fixed—
Scalenus medius.
To close the glottis:
Constrictor glottidis.
To open the glottis:
Thyreo-arytenoideus.
To approximate the tracheal rings:
Tracheo-lateralis.
To tense the inferior larynx:
Broncho-trachealis posticus,
Broncho-trachealis anticus,
Broncho-trachealis brevis,
Bronchialis posticus,
Bronchialis anticus.
To relax the inferior larynx:
Sterno-trachealis.
To aid in respiration:
When the first rib is fixed—
Intercostales.
When wing is fixed—
Latissimus dorsi,
Dermo-cleido dorsalis.
When the scapula is fixed—
Serratus magnus anticus,
Serratus parvus anticus,
Thoraco-scapularis,
Levatores costarum,
Appendico-costales,
Triangularis sterni.
To flex the shoulder-joint:
Latissimus dorsi.
To elevate the humerus:
Latissimus dorsi.
To draw the scapula forward:
Trapezius,
Rhomboideus.
To close the wing:
Teres et infraspinatus.
To extend the humerus:
Coraco-humeralis,
Scapulo-humeralis.
To pull the humerus upward and backward:
When the scapula is fixed—
Supraspinatus.
To pull the coracoid outward:
Subclavius.
To depress the wing:
Coraco-brachialis.
To depress the scapula:
When the ribs are fixed—
Thoraco-scapularis.
To rotate the humerus:
Subscapularis.
To flex the forearm:
Pronator brevis,
Biceps,
Brachialis anticus,
Anconeus,
Tensor patagii longus,
Tensor patagii brevis.
To extend the arm:
Deltoid.
To extend the antibrachial region:
Triceps.
To raise and to draw the hand forward:
Extensor metacarpi radialis longior.
To extend the digit:
Extensor indicis longus,
Extensor digitorum communis,
Extensor proprius pollicis,
Interosseous dorsalis.
To supinate the radial region:
Supinator brevis.
To flex the hand:
Flexor metacarpi radialis.
To pronate the forearm:
Pronator brevis,
Pronator longus.
To extend the hand on the forearm:
Extensor ossis metacarpi pollicis.
To flex the digit:
Flexor minimi digiti,
Flexor digitorum sublimis,
Flexor brevis pollicis,
Flexor digitorum profundus,
Interosseous palmaris.
To flex the hand upon the forearm:
Flexor carpi ulnaris,
Flexor carpi ulnaris brevior.
To rotate the hand toward the body:
Flexor carpi ulnaris brevior.
To abduct the digits:
Abductor minimi digiti.
To flex the metacarpus:
Flexor metacarpi brevis.
To extend the leg:
Sartorius.
To adduct the thigh:
Sartorius,
Adductor longus,
Adductor magnus.
To abduct the thigh:
Gluteus primus,
Gluteus medius,
Gluteus minimus.
To pull the thigh forward:
Gluteus minimus,
Gluteus medius.
To extend the leg upon the thigh:
Extensor femoris,
Vastus internus.
To extend the leg upon the knee:
Vastus internus.
To flex the leg upon the thigh:
Biceps flexor cruris,
Semitendinosus,
Semitendinosus accessorius,
Semimembranosus.
To pull the tail down and to one side:
Femoro-caudal.
To pull the head of the femur backward:
Obturator externus.
To act as a posterior stay to the head of the femur:
Obturator internus.
To pull the pelvis forward and to steady it on the head of the femur:
Gemellus,
Obturator internus,
Obturator externus.
To extend the metatarsus on the tibia:
Gastrocnemius,
Soleus,
Tibialis posticus.
To flex the toes:
Peroneus longus,
Flexor perforatus medius primus pedis,
Flexor perforatus indicis secundus pedis,
Flexor perforatus medius secundus pedis,
Flexor perforatus indicis primus pedis,
Flexor perforans digitorum profundus,
Flexor longus hallucis,
Flexor perforatus annularis primus pedis.
To flex the metatarsus on the tibia:
Tibialis anticus.
To extend the toes:
Extensor longus digitorum,
Extensor hallucis brevis.
To flex the back laterally and to aid in raising the body.
Sacro-lumbalis,
Longissimus dorsi.
To elevate the tail:
Levator coccygis,
Levator caudæ.
To depress the tail:
Depressor caudæ,
Infracoccygis.
Together—
Depressor coccygis,
Lateralis caudæ.
To pull the tail downward and to one side:
Singly—
Lateralis coccygis.
Depressor coccygis,
Lateralis caudæ.
To close the eyelids:
Orbicularis palpebrarum.
To raise the superior eyelid:
Levator palpebræ superioris.
To pull the lower eyelid downward:
Depressor palpebræ inferioris.
To pull the membrana nictitans over the eyeball:
Quadratus nictitans,
Pyramidalis nictitans.
To rotate the eyeball:
Obliquus superior,
Obliquus inferior.
To pull the eyeball upward:
Rectus superior.
To pull the eyeball downward:
Rectus inferior.
To pull the eyeball outward:
Rectus externus.
To pull the eyeball inward:
Rectus internus.
To tense the ear drum:
Tensor tympani.
To relax the ear drum:
Circumconcha.
To depress the humerus:
Pectoralis major.
To raise the humerus:
Pectoralis secundus,
Pectoralis tertius.
Footnote 5:
Muscles are arranged in pairs. Singly means one muscle acting alone,
_i.e._, without its fellow; together means acting both at the same
time.
SPLANCHNOLOGY
=The Digestive Apparatus.=—This apparatus, apparatus digestorius,
consists of the organs directly concerned in the reception of food, in
its passage through the body, and in the expulsion of the unabsorbed
portion. For convenience, these organs are grouped as follows: the
alimentary canal and the accessory organs.
The alimentary canal is a tube which extends from the mouth to the anus.
It has a complete lining of mucous membrane, external to which is an
almost continuous muscular coat. The abdominal portion of the tube is
largely covered with a serous membrane, the visceral peritoneum. The
canal consists of the following consecutive segments: mouth, pharynx,
first portion of the esophagus, crop, second portion of the esophagus,
proventriculus, gizzard, small intestine, large intestine, and cloaca.
The accessory organs are beak, tongue, salivary glands, liver, and
pancreas.
=The Mouth= (Fig. 27).—The distinctive character of the mouth of the
fowl consists, in the absence of lips and teeth and instead of jaw bones
of other animals, of a _beak_. The edge of the beak is covered by a
horn-like gum. The shape of the beak differs in the various classes of
birds. In the chicken the beak is short, strong, thick, and pointed; in
palmipeds it is flattened. The upper mandible extends out over the lower
mandible. The outer portion of the upper and the lower beaks is covered
by a horny sheath. There is no velum, and the mouth cavity is extended
rather continuously into the pharynx (Fig. 27, No. 4). The posterior
cross bar of the hard palate (Fig. 27, No. 5), which possesses a row of
filiform papillæ projecting backward, marks the upper boundary line of
the mouth; while the posterior end of the tongue (Fig. 27, No. 6),
likewise with a row of filiform papillæ, marks its lower boundary line.
_Parts of the Mouth._—The mouth of fowls is divided into an upper and a
lower half. The upper half is divided into an anterior and a posterior
part.
The anterior part extends from the anterior tip of the beak to the
posterior nares. It is further divided into an outer hard part and an
inner soft part. The outer part is covered by epithelium which may be
considered as a continuation from the upper outer portion of the beak. A
portion of this is cornified. The inner part is covered by a mucous
membrane containing mucous glands, nerves, and blood-vessels.
In the posterior part of the upper half of the mouth, are situated the
posterior nares (Fig. 27, No. 10) which appear as a longitudinal slit in
the center of the hard palate. There is also found in this part a furrow
which contains the opening of the Eustachian tubes, or tubæ auditivæ.
There are also two ridges near the same posterior part in which are red
and white papillæ, which may appear in rows, and which contain mucous
glands.
[Illustration:
FIG. 27.—Mouth and pharynx of a cock laid open. 1, Eye. 2, Edge of
beak covered with a horn-like gum. 3, Tongue. 4, Pharynx. 5,
Posterior cross bar of hard palate. 6, Posterior end of tongue. 7,
Anterior end of esophagus. 8, Phrenum. 9, Palatal papillaries. 10,
Posterior nares.
]
The lower half of the mouth lies between the lower jaw bones and the
walls of the mouth cavity. The tongue is attached here by means of the
phrenum (Fig. 27, No. 8). This half of the mouth forms a pocket-like
structure which aids in taking up the food.
The mouth cavity is lined with stratified squamous epithelium,
continuous with that of the pharynx and the esophagus. Taste buds are
located in the mucous membrane of the mouth.
[Illustration:
FIG. 28.—Various anatomical parts of the fowl.
_C._ A section through the nasal region of the fowl. 1, Nasal passages
showing the turbinated bones dividing the nasal passage into the
superior, middle and inferior meati. 2, The infraorbital sinus. 3,
The hard palate.
_D._ Herbst’s touch corpuscle from the beak of a quail.
_E._ A vertical section through the ductus cochlearis of a pigeon. 1,
A blood-vessel. 2, The periosteum. 3, The bony structure. 4, The
vascular integument. 5. The scala vestibuli. 6, The inner hyaline
cylindrical cells. 7, The membrana tectoria. 8, The papilla acustica
basilaris. 9, The membrana basilaris. 10, The scala tympani. 11, The
ganglion of the cochlear nerve in the ramus basilaris. 12, The
periosteum (Gadow).
_F._ A corpuscle of the soft papilla of a duck’s tongue.
_J._ A transverse section through a feather papilla. 1, The pulp. 2,
The malpighian layer. 3, The corium. 4, The stratum corneum of the
papilla. 5, The malpighian cell group of the main shaft. 6, The
horny sheath.
]
In many water fowls, as geese and ducks, the gum edge of the mandible
has grooves extending crosswise, in which are numerous terminals of the
trigeminus nerve arranged as taste organs (Fig. 29, _G_ and Fig. 28, _D_
and _F_). In many birds of prey and in water birds, _e.g._, the goose
and the duck, there is found at the base of the beak, a very thin,
nervous or sensitive skin, waxy in appearance, called the ceroma.
[Illustration:
FIG. 29.—Various anatomical parts of the fowl.
_A._ 1, The superior semicircular canal. 2, The vestibular nerve. 3,
The meatus auditorius internus—the entrance of the auditory nerve.
4, The entrance of the cochlear nerve. 5, Posterior semicircular
canal. 6, The ampulla.
_B._ Side papilla of the tongue. 1 and 2, Papillæ showing a fibrous
central core supporting blood-vessels and nerves. 3, The basement
membrane consisting of connective tissue.
_G._ Herbst’s corpuscle of the tongue of a duck, showing the capsule,
lamella and around the nerve zone, numerous round bodies arranged in
two rows.
_H._ From the cristæ acoustica of the ampulla of the dove. A, A
vertical section with isolated fiber cells. 1 and 2, The nerve
fibers. 3, The hair cells.
_I._ A longitudinal section through a feather papilla showing a young
feather. 1, The developing feather. 2, The horny sheath. 3, The
epithelium. 4, Stratum corneum. 5, Stratum malpighi. 6, Corium. 7,
Malpighian cell group of the follicle.
]
_The Hard Palate._—The hard palate, palatum durum, forming the roof of
the mouth has for its boundaries the beak anteriorly, the mandibular
arches laterally, and the pharynx posteriorly. It has four or five
transverse bars, projecting posteriorly from each of which is a row of
filiform papillæ (Figs. 27 and 29).
[Illustration:
FIG. 30.—A section through the wall of the crop of a hen. 1, The outer
muscular layer showing longitudinal fibers. 2, The inner muscular
layer showing the sectioned ends of the bundles of muscle fibers. 3,
Stratified squamous epithelium. 4, The outer surface or lumen of a
fold. 5, The stroma, muscularis mucosa, and submucosa.
]
The _beak_ (Fig. 4, No. 1) with little if any aid from the tongue, is
the prehensile organ.
=The Tongue= (Fig. 27, No. 3). _Location._—The tongue (lingua) of the
fowl is situated in the floor of the mouth between the rami of the lower
mandible, and is slung to the cranium by the cerato-branchial element of
the os hyoideum (Fig. 18, No. 2).
_Shape._—The tongue, is pointed in front and wide behind, shaped like an
Indian arrow-head, and is supported by the bony and cartilaginous hyoid
apparatus (Fig. 9, _A_).
[Illustration:
FIG. 31.—The visceral organs of the hen. 1, Tongue. 2, Larynx. 3,
Glottis. 4, First portion of the esophagus. 5, Crop. 6, Second
portion of the esophagus. 7, Proventriculus. 8, Duodenum. 9, Free or
floating portion of the small intestine. 10, Mesentery supporting
the free portion of the small intestine. 11, Cæca. 12, Rectum or
large intestine. 13, Cloaca. 14, Anus. 15, Liver. 16, Gall-bladder.
17, Pancreas. 18, Gizzard. 19, Trachea. 20, Lungs. 21, Spleen.
]
_Structure._—The free part of the tongue consists of two long tubes
which are formed by the rolling in of the ventral sides of its horny
coverings. The _dorsal plate_, which constitutes one-half of the horny
sheath, does not form a part of the tubes, but ends in the region of the
point of the entoglossum.
The top surface is covered by a thick stratum corneum, giving it a
rather horny surface. Glands occur in the posterior part of the tongue.
While not so freely movable as in mammals, the tongues of birds are very
flexible.
=The Pharynx= (Fig. 27). _Location._—The anterior part of the pharynx
joins with the mouth and the posterior part with the upper portion of
the esophagus and the superior larynx. The pharynx is bounded anteriorly
by the base of the tongue and by the posterior edge of the hard palate.
Posteriorly, it is marked by the entrance of the esophagus and by a
ridge of filiform papillæ located on the supero-posterior part of the
larynx, called the palatal papillaries. A few filiform papillæ stud the
roof. The pharynx communicates anteriorly with the posterior nares and
the mouth, and, posteriorly, with the esophagus and the larynx.
_Shape._—The pharynx is a musculo-membranous sac.
_Structure._—The pharynx is lined with a mucous membrane covered by
squamous epithelium. The mucous membrane is thrown into irregular folds.
The bird has two Eustachian tubes. Pneumatic apertures conduct the air
from the Eustachian tubes to the pericranial diploë.
In the posterior pharyngeal roof is situated the infundibular crevice.
_Function._—The function of the pharynx is to give passage for the air
from the posterior nares to the larynx, and to give passage for the food
from the _mouth_ to the esophagus.
=Glands Adjacent to the Mouth and to the Pharynx.=—The mucous membrane
adjacent to the glottis and in the roof of the mouth contains alveolar
glands. The _angular gland_ of the mouth, located beneath the zygomatic
arch, by some anatomists is considered the rudimentary parotid gland.
The _sublingual glands_, or glandulæ sublinguales, are well developed
(Fig. 17, No. _B_, 4). They form conical masses, with the apex directed
anteriorly, and occupy a portion of the intermaxillary space. Several
ducts from these glands open into the mouth cavity. In the palatine
region there are also located glands called the _palatine glands_, which
open by many stomata upon the surface.
=The Esophagus= (Fig. 18, No. 6). _Location and Shape._—The esophagus is
a musculo-membranous tube, capable of great distension, which extends
from the pharynx to the proventriculus (Fig. 35, No. 1, and 3).
The esophagus communicates anteriorly with the pharynx. It extends down
the neck, lying supero-laterally with regard to the trachea and toward
the right side. It enters the thorax above the trachea, and, passing
through between the bronchi, terminates into the proventriculus. At the
entrance of the thorax and just to the right of the median line, it
expands into the crop which divides it into two portions, designated as
the first and the second. The first portion of the esophagus is the
longer, the length depending upon the size and kind of fowl.
_Structure._—The wall is composed of four coats, the mucous membrane,
the submucosa, the muscular coats, and the fibrous sheath or tunic. The
mucous membrane is pale and is covered with stratified squamous
epithelium.
The mucous membrane is loosely attached to the muscular coat by the
submucosa. Except during deglutition it lies in longitudinal folds which
obliterate the lumen. Opening from the mucosa are lenticular glands,
which may be seen on inflating an esophagus and looking through its
transparent walls.
The muscular coat of the esophagus is divided into two layers, an outer
longitudinal and an inner circular layer.
The outer fibrous sheath connects the esophagus loosely to the
surrounding structures.
_Function._—The function of the esophagus is to give passage way for the
food from the pharynx to the crop and from the crop to the
proventriculus.
=The Crop= (Fig. 35, No. 2; Figs. 30 and 31). _Location and Shape._—The
crop, or ingluvies, saccular in shape, is located at the entrance of the
thorax and just to the right of the median line. The first portion of
the esophagus empties into the crop superiorly and inferiorly the crop
opens into the second portion of the esophagus. Like the esophagus the
crop is capable of great distension.
_Structure._—The wall of the crop is composed of four coats, the mucous
membrane, submucosa, muscular and the outer fibrous.