LABORATORY ANATOMY
OF THE TURTLE
LAURENCE M. ASHLEY, Ph.D.
Professor of Zoology
Walla Walla College
College Place, Washington
First Edition
Illustrated by
CARL PETTERSON
WM. C. BROWN COMPANY
jPu h litk ers
DUBUQUE, IOWA
QL
A&3
Copyright 1955
by
Laurence M. Ashley
The LABORATORY ANATOMY Series
Edited by Ernest S. Booth
Laboratory Anatomy of the Cat
Ernest S. Booth, 1943, 1946, 1948
Laboratory Anatomy of the Shark
Laurence M. Ashley, 1950
Laboratory Anatomy of the Fetal Pig
Theron O. Odlaug, 1951, 1955
Laboratory Anatomy of the Frog
Baymond A. Underhill, 1951
Laboratory Anatomy of the Turtle
Laurence M. Ashley, 1955
Other Subjects in Preparation
IHE UNIVERSITY OF MICHIGAN LIBRARIES
MtnufictHTtd by WM. C. BROWN CO. INC., Dubuque, Iow»
Printed in U. S. A.
I
I
r
lear nerve between the dura mater and the skull
and enters the semilunar ganglion from which its
fibers, as part of the main trigeminal trunk, pass'
into the brain. The maxillary nerve traced pos-
teriorly comes from two branches, one passing
below the orbit and the other coming up diagonal-
ly across the floor of the orbit to join its mate at
the posterior orbital wall. From here the maxil-
lary passes between muscles to enter the skull.
At this point it is joined by the mandibular branch
coming up from the lower jaw. The trunk formed
by the union of these two nerves enters the skull
through a foramen and promptly joins the semi-
lunar ganglion from which its fibers parallel those
of the ophthalmic as they pass into the brain.
VI. Abducens nerves, these spring from near
the midventral line medial to the roots of the
facial (VII) and acoustic (VIII) nerves. Do not
attempt to see the abducens until after the re-
mainder of the cranial nerves have been traced.
VII. Facial nerves. These arise in company
with the acoustic (VIII) nerves from the lateral
-wall of the medulla and just posterior to the tri-
geminal roots. They at once separate into the
facial nerve passing through the capsule of the in-
ner ear anteriorly and the acoustic next to be de-
scribed. The facial soon passes rostrad out of
the skull over the anterior horn of the hyoid bone
and innervates muscles between the hyoid and the
lower jaw. In order to further trace the seventh
as well as the ninth, tenth, and twelfth nerves
proceed as follows: remove the skin and adjacent
muscles from the hyoid bones on the ventral side
of the head, locate the anterior and posterior horns
of the hyoid, and identify the nerves mentioned
above, in turn, as described below.
VIII. Acoustic (auditory) nerve. It arises in
company with the facial and passes promptly into
the inner ear capsule to divide into an acoustic
branch to the cochlea and a vestibular branch to
the semicircular canals and vestibule.
IX. Glossopharyngeal nerve. It arises as sev-
eral small roots just posterior to the acousticofacial
-roots on the lateral walls of the medulla. These
nerves exit from the skull by passing through the
posterior wall of the ear capsules and forward
between the two horns of the hyoid on either side
to supply, adjacent muscles as well as the lining
of the mouth and pharynx.
X. Vagus nerve. It springs from several root-
lets along the side of the medulla just posterior
to the ninth nerve roots. These two nerves leave
the skull together with the eleventh and twelfth
nerves. Now locate the vagus (vagosympathetic)
trunk in the neck and follow it into the skull by
dissecting longitudinally through the floor of the
mouth and pharynx into their cavities. Turn back
the two flaps formed by this incision and remove
the mucous membrane from the roof of the
pharyngeal cavity. Here the hypoglossal nerve
(twelfth) will be seen passing ventral to the vagus.
At about this point the vagus enters the superior
cervical sympathetic ganglion from which several
nerves emerge, some (or one) of which enter the
skull and medulla as the vagus roots.
XI. Spinal accessory. Like the vagus the spinal
accessary is formed from several roots which
emerge from the posterior medulla to exit from
the skull in company with the vagus. The ac-
cessary nerves supply motor impulses to the
muscles of the neck.
XII. Hypoglossal nerves. These emerge from
the posterior medulla near the mid-ventral sulcus.
They can best be seen by first cutting the roots
of the vagi and accessories on one side so as to
uncover them. Traced rostrad into the throat the
hypoglossal supplies motor fibers to muscles of the
anterior hyoid horn and to the tongue.
B. Ventral view of the brain, fig. 41. Removal
of the brain from the skull is required in order
to study the ventral (basilar) surface. First, gent-
ly lift the olfactory bulbs and (if not done before)
cut the optic nerves which lie side by side just
beneath the bulbs.
1. Optic chiasma, a fusion of the two optic
nerve trunks beneath the olfactory bulbs. A par-
tial crossing of nerve fibers to the opposite side oc-
curs at this point.
43
but larger than that of amphibians. It functions
as the principal center of equilibrium and muscu-
lar coordination of the brain.
5. Medulla oblongata (hindbrain), a caudally
tapering region continuous with the spinal cord
posteriorly.
a. Tela choridea, a thin roof of the fourth ven-
tricle or cavity of the medulla. The tela choroidea
is similar in structure and function to the choroid
roof of the diencephalon, each serves to secrete
nutritive cerebral fluid into the cavities (ventricles)
of the brain.
b. Somatic sensory columns, the dorsal mar-
gins of the medulla.
c. Auricular lobes, small lobations of the cere-
bellum representing the anterior continuations of
the somatic sensory columns. These columns con-
vey sensations to the cerebrum and cerebellum
from outside the body and from the body wall.
d. Somatic motor columns, fiber bundles paral-
leling the midventral groove in the floor of the
medulla and conveying impulses for muscular con-
, traction from the cerebrum and cerebellum to the
somatic muscles.
6. Cranial nerves, figs. 41-43. In the turtle,
as in amniotes in general, there are twelve pairs
of cranial nerves instead of but ten pairs as in
anamniotes. You should memorize both the num-
ber and the name for each of the cranial nerves.
I. Olfactory nerves. There is one from each
olfactory sac to each olfactory bulb. They carry
impulses for the sense of smell.
II. Optic nerves. These will be seen after
cutting through the olfactory nerves and lifting
the anterior end of the brain slightly. Optic
nerves are rather stout trunks which carry visual
impulses from the eyes to the optic lobes. These
nerves enter the cerebrum ventrally on either
side.
III. Oculomotor nerves. They leave the floor
of the midbrain just anterior to the trochlear
nerves (IV). They are visible only after pressing
the cerebral hemisphere away from the skull. The
oculomotor nerve can be further traced by loosen-
ing the eyeball ventrally and lifting it so as to
reveal the loose tissues between the eyeball and
the orbital floor. Remove loose connective tissue
down to the glandular tissues so as to be able to
see these nerves. Usually adherent to the eyeball
is a portion of the maxillary branch of the tri-
geminal (V). Loosen this nerve from the eye-
ball, cut the pyramidal muscle, lift the eye up-
wards and mediad, then cut the inferior and ex-
ternal rectus muscles between and above which
will be found the heavy white trunk of the optic
nerve (II). The oculomotor nerve contacts the
ventral side of the optic nerve and supplies the
four following extraocular muscles: superior, in-
ferior, and anterior rectus, and inferior oblique.
IV. Trochlear nerves. On the dorsal side of
the midbrain, in the dorsolateral angles between
optic lobe and cerebellum, will be seen the small
trochlear nerves. By pressing the cerebral hemi-
spheres away from one orbit a trochlear nerve
will be seen to pass behind the oculomotor toward
the orbit which it enters.
Cut the superior oblique muscle at its insertion
on the eyeball and look beneath this muscle to
find the trochlear nerve which innervates it. An-
other nerve running medial to the trochlear is
the ophthalmic branch of the trigeminal (V).
V. Trigeminal, the thickest of the cranial
nerves. These originate from about the middle of
the ventral wall of the medulla and pass laterad
to enter a large semilunar ganglion located in a
fossa in the medial wall of the skull. From the
ganglion, on either side, three branches pass an-
teriorly one above another. From above they
are the ophthalmic distributed to tissues around
the eyes, the maxillary innervating the face, and
the mandibular distributed to the lower jaw. Un-
cover the ophthalmic and maxillary nerves by re-
moving an eyeball without injury to these nerves.
Sever the nerves lying anterior to the trigeminal
and raise the brain gently drawing it toward one
side to reveal the ophthalmic nerve. This nerve
may now be traced anteriorly into the olfactory sac.
Traced from the orbit to the brain the ophthalmic
enters the skull, travels in company with the troch-
42
CHAPTER VII
Nervous System
The brain and spinal cord are relatively smaller
in the turtle than in animals with cartilaginous
skeletons such as the shark. However, a careful
study of the nervous system of the turtle is both
interesting and profitable owing to its higher de-
gree of development and complexity. Care must
be exercised in opening the skull as well as in re-
moving the brain lest important structures be dam-
aged or destroyed. A pair of bone shears will be
useful in removing the top of the skull (skull cap).
This permits study of the dorsal view of the brain
without its being disturbed. This view should,
therefore, be studied before the ventral and lat-
-eral surfaces are examined.
THE BRAIN
A. DORSAL SURFACE, fig. 43.
This is clearly seen only after complete re-
moval of the skull "cap," as directed above, and
the meninges now to be described.
1. Meninges, membranes covering the brain
and spinal cord.
a. Dura mater, a tough membrane lying be-
tween the brain and the skull.
b. Pia mater, a thin membrane which intimate-
ly covers the brain surface to which it is closely
adherent.
c. Subdural space, a narrow space lying be-
tween the two above membranes. It is criss-
crossed by numerous membranous cords passing
between the dura and the pia maters.
d. Peridural space, a narrow space lying be-
tween the skull and the dura mater.
Remove as much as you can of the dura mater
from the dorsum of the brain.
2. Cerebral hemispheres, a pair of conspicuous
swellings forming two halves of the cerebrum,
the largest of the several regions of the brain.
The hemispheres are separated midlongitudinal-
ly by a deep superior longitudinal fissure. In
turtles they are relatively much larger than those
of fishes and amphibians. The lateral surface of
each hemisphere is extended to form a flattened
temporal lobe.
a. Olfactory bulbs or lobes, a pair of elongated
triangular anterior extensions from the cerebral
hemispheres. These bulbs each receive an ol-
factory nerve from an olfactory sac, (one sac on
either side in the nasal cavities).
b. Choroidal sac, a very thin sac adhering to
the dura mater. It is often torn off when removing
the dura. This "sac" lies between the posterior
ends of the cerebral hemispheres where it forms
a choroidal roof for the diencephalon.
c. Pineal body (epiphysis), a small body lying
upon the choroidal sac to which it is attached.
It lies in the triangle formed by the posterior
separation of the cerebral hemispheres.
Remove the choroidal sac and note the cavity
of the diencephalon which is a shallow depression
in the brain floor just caudad of the cerebral
hemispheres.
3. Optic lobes, a pair of prominent subspheri-
cal bodies just caudad of the cavity of the dience-
phalon. They form a large part of the midbrain
region being important centers in the visual sys-
tem.
4. Cerebellum, a posteriorly projecting pair of
lobes which overhang the anterior end of the
medulla oblongata. The cerebellum is relatively
smaller than that of selachians (elasmobranchs)
41

Fig. 40—Male urogenital syst. ventral.
40
1. Penis, a dark mass visible through the ven-
tral cloacal wall. A penis is not present in anam-
niotes but does occur in reptiles, also in some
birds, and in all mammals. Attached to the ven-
tral cloacal wall are muscles which retract the
penis. Its eversion is achieved by vascular en-
gorgment of the paired corpora cavernosa penis,
rounded spongy tissue masses projecting laterally
at each side of the neck of the bladder from the
anterior cloacal wall. Its midlongitudinal urethral
groove terminates caudad in a heart-shaped glans
penis.
2. Kidneys, previously seen as lobed organs
flattened against the postero-dorsal walls of the
pleuroperitoneal cavity.
3. Testes, male gonads. Each testis is a spheri-
cal organ of yellowish color attached to the ventral
side of each kidney by a mesentery termed the
mesorchium.
4. Epididymis, a dark, elongated structure of
coiled tubules, one of which lies postero-lateral
to each kidney. Each testis receives, in its anter-
ior pole, a series of minute efferent ductules from
the testis of its own side. These ductules convey
sperm cells from testis to epididymis and they
traverse the mesorchium en route. Efferent duct-
ules and epididymis are derived from embryonic
mesonephric tubules and ducts.
5. Ductus deferens (deferent ductule), derived
from the mesonephric duct also. It is much coiled
anteriorly where it may be termed the epididymi-
dal duct. Remove its peritoneal covering and un-
coil it posteriorly, thus tracing it to its cloacal
orifice which lies cephalad of, and basal to, the
bulbs of the corpora cavernosa. These bulbs,
which when the penis is retracted extend craniad
along either side of the bladder-stalk, are the an-
terior swellings of the corpora cavernosa. Filling
of the corpora cavernosa with blood from the in-
ternal iliac vein causes erection of the penis at
the time of mating. The walls of the urethral
groove meet dorsally to form a duct for the
passage of spermatozoa.
6. Ureters. These convey urine from kidneys
to the cloaca. The ureters lie on the kidney s
ventral face and may be seen by removing the
epididymis from the kidney. Each ureter is a
short uncoiled tube the cloacal orifice of which
is just anterior to that of the ductus deferens of
the same side. These openings are at the anterior
end of the urethral groove.
7. Accessory bladders. As in the female, A-6
above. Find and probe these bladders to dis-
cover their openings into the cloaca.
39
St
f: 3 7/
Preface
One of the most interesting vertebrates to study in comparative anatomy
is the turtle. Some may think it either too difficult for class dissection
or too atypical a reptile to be included in the course. Actually it requires
but little dissection — mainly removal of the ventral armor (plastron) and
breaking away of sufficient of the dorsal armor (carapace) to enable visual-
ization of internal parts. Furthermore, the turtle is one of the most readily
available and inexpensive of North American reptiles. Except for its
armor is it an excellent example of a vertebrate whose anatomy is inter-
mediate between that of a typical amphibian and that of a typical bird.
This manual is intended as a laboratory guide to the dissection of the
turtle. Numerous labeled drawings are included so that the student may:
(1) progress rapidly and intelligently;
(2) make fewer errors in dissection;
(3) have ready access to correctly labeled drawings for review; and
(4) save valuable time which will be spent reviewing for oral quizzes
covering his dissections and in making additional dissections.
It is suggested that laboratory grades be based upon quality of dis-
section as well as performance on oral quizzes. Students will generally
appreciate not being required to make their own drawings, and grading will
be more equitable when those having artistic ability are given no better
chance for high grades because of making superior drawings. The time
required of laboratory instructors may be reduced since oral quizzes can
be given during the laboratory period and because students will have
fewer questions owing to the labeled drawings.
This method of laboratory study encourages more careful dissection
and observation and requires further use of the specimen dissected each
time the student appears for an oral quiz. It is further suggested that
instructors require students to demonstrate structures called for, rather
than pointing them out for the student to name.
Constructive criticism and suggestions for the improvement of this
manual will be gratefully received by the author.
College Place, 1954.
L. M. Ashley.
Introduction
Painted turtles or terrapins are commonly used
in the study of the anatomy of the turtle. Turtles
are reptiles belonging to Phylum CHORDATA,
subphyllum Vertebrata-, class Reptilia, orders Che-
Ionia or Testudinata, families Chelydridae or
Testudinidae, genera Chelydra, Chrysemys, or
Pseudemys and to any one of several different
species. Since a variety of species and genera
are sold for dissection it is not always possible to
obtain the scientific name of the turtles purchased
without the use of a key and even then it must
rirst be known just where the specimen was col-
ected in order to know what key to use.
Before beginning to dissect you should become
amiliar with the following suggestions regarding
aboratory work:
1. When possible, separate organs without cut-
ing (blunt dissection).
2. Use teasing needles, probes, etc., in prefer-
nce to scalpels or scissors, whenever possible.
•3. Ask questions only when they cannot be
nswered by reading your manual.
4. When you really need help do not hesitate
) call upon the instructor for assistance.
5. Variation is the rule in nature, therefore,
you may expect to find differences in the anatomy
of certain muscles, blood vessels, etc., from time
to time. Marked deviations from the normal
should be called to the attention of the instructor
so that they may be demonstrated before the
entire class.
The drawings in the manual represent the usual
condition to be found in terrapins and in painted
turtles but in most respects the anatomy of these
forms is the same as that of all turtles and even
tortoises, with minor exceptions.
6. You will profit by looking about at some of
the dissections of other students from time to time
but remember to do your own dissection so well
that you can satisfactorily demonstrate any struc-
ture called for in the oral quizzes.
7. In addition to the usual dissecting tools it
is desirable to have a cheap pair of pliers or a pair
of bone shears for breaking off pieces of carapace
when dissecting.
2
CHAPTER I
External Anatomy and Exoskeleton
Study the external form and structure of your
turtle. Its longitudinal axis is relatively shorter
than that of most vertebrates but its transverse axis
is much greater. The body is so constructed as to
be well adapted to life either on land or in the
water. Although slow-moving on land it can
swim rapidly and, its vital organs are well pro-
tected by dorsal and ventral shields, the carapace
and the plastron.
A. HEAD.
Observe its reptilian form, the strong bony skull
and jaw giving ample protection to the special
sense organs. Note the covering of the head—is it
naked, scaled, or with well-marked head shields?
Is the jaw and throat region similarly covered?
3n the tip of the snout find the anterior nares, a
pair of openings leading into the air passages of
the respiratory tract. Observe the horny beaks
covering the jaws. Are each of these pointed
anteriorly in the midline? The horn is epidermal
in origin and forms part of the exoskeleton. Ex-
amine the eyelids, both upper and lower, and find
the nictitating membrane in the anterior corner
of each eye. Next find the tympanic membrane
(eardrum) on either side just behind the angle of
the jaw. If this is not externally evident wait
until the anatomy of the anterior part of the
mouth is described (see Chapter IV) when it can
be located by probing from within outwards.
B. NECK.
Turtles have long necks but they are especially
long in snapping and in soft-shelled turtles. Note
the skin covering the neck of your turtle and
determine whether it is smooth or wrinkled and
whether it is loose or tight.

NUCHAL SCUTE
NUCHAL PLATE
9th VERTEBRA
VERTEBRAL SCUTE
VERTEBRAL PLATE
COSTAL SCUTE
4th RIB
3rd COSTAL PLATE
MARGINAL SCUTE
MARGINAL PLATE
PYGAL PLATE

Fig. 1—Carapace, dorsal view
Fig. 2—Carapace, ventral view
TRUNK.
The trunk contains the main visceral mass of
e body. It is made firm and rigid by the large
my carapace above, and the almost flat plastron
low. Carapace and plastron are strongly united
i each side by bony bridges varying in width

Fg. 3—Plastron, ventral view
I
LIMBS.
Forelimbs and hindlimbs are alike supplied with
e toes each. The toes (digits) each exhibit a
iw except the fifth (little) toes on the hindfeet.
le legs are supplied with powerful muscles
chapter III) in order to provide for rapid swim-
ing, or walking on land. Spread apart the toes
a fore and hind-foot noting the webbing of
in between the toes.
TAIL.
This appendage is short in the painted turtle
Ihrysemys) but is rather long in the snapper
with the species. Horny shields (scutes) cover
these rigid structures externally forming the major
portion of the exoskeleton. Learn the name and
location of each kind of scute, and bony-plate
(endoskeleton) of the carapace and of the plastron.
Figs. 1-4.

Fig. 4—Plastron, dorsal view
(Chelydra). The rounded anal opening appears
on the ventral side near the base of the tail.
F. SUMMARY.
The body surface is covered with either a tough
dark skin or with horny plates or shields. Horny
plates cover jaws, carapace, plastron and bridges
— skin covers the remaining surfaces. External
orifices of mouth, nostrils (nares), and anus pro-
vide necessary openings for the digestive and the
respiratory tracts.
GULAR
EPIPLASTRON
ENTOPLASTRON
HUMERAL
PECTORAL
HYOPLASTRON
ABDOMINAL
HYPOPLASTRON
FEMORAL
XIPHIPLASTRON
ANAL
4
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CHAPTER II
Skeletal Systems (The Endoskeleton)
The first part of the skeleton, the exoskeleton,
vas considered in Chapter I. The endoskeleton
» the second part of the skeletal system. It is
lerived partly from cartilage by replacement of
artilage by bone, and partly from membranes or
onnective tissues, by intramembranous ossifica-
ion. For the study of the endoskeleton it is neces-
ary to have available specially prepared skeletons,
loth articulated and disarticulated skeletons are
esirable. First study the articulated skeleton
fter which study separate bones, if these are
vailable.
The study of the endoskeleton requires a knowl-
dge of various bony fusions or joints. Skull bones
re firmly united by immovable suture joints
;ynarthroses). Such joints consist of more or less
interlocked toothed edges of the bones thus united.
Joints may be slightly movable (amphiarthroses),
or freely movable (diarthroses) as in the limbs.
Certain smaller or larger holes (foramina)
through bones will be noticed. Only the major
foramina will be mentioned in this manual. Other
features of bones include such projections as
spines, condyles, tuberosites, and other so-called
processes of bones. These are specifically men-
tioned only when they seem to be of special im-
portance in comparative anatomy.
The endoskeleton consists of two divisions, the
axial skeleton consisting of the skull, vertebrae,
and ribs, and the appendicular skeleton consist-
ing of the limb bones together with the girdle
PREMAXILLA
EXTERNAL NARES
PREFRONTAL
NASAL ORBIT
MAXILLARY
FRONTAL
POSTFRONTAL
LACRIMAL
PREFRONTAL JUGAL
ADLACRIMAL
PARIETAL
SUPRAOCCIPITAL
ORBIT
OPISTHOTIC
FRONTAL
POSTORBITAL BAR
POSTFRONTAL
INFRATEMPORAL FOSSA SQUAMOSAL
PARIETAL OCCIPITAL CONDYLE
| OUADRATE
9 SUPRAOCCIPITAL
SUPRATEMPORAL FOSSA

Fig. 5—Alligator skull, dorsal Fig. 6—Turtle skull, dorsal
anes. The girdles serve to attach the limb bones
i the body or to the axial skeleton.
The bony plates of the carapace and plastron
ive been noted in Chapter I.
AXIAL SKELETON
A. SKULL. This consists of two portions, the
anium (brain case) and the visceral skeleton,
iat is, the bones and cartilages of the upper jaw,
ie suspensorium of the lower jaw, the lower jaw
self, and the hyoid apparatus.
1. CRANIUM. Study the dorsal and lateral
pects of the skull, figs. 5-8, and learn the names
the bones shown by identifying them on your
rtle skull. Next study the ventral skull bones,
5s. 9 and 10. The alligator skull is also shown
r comparison with the turtle skull.
; PARIETAL

OUADRATOJUGAL
I I
PREFRONTAL |
POSTF RONTAL

TRANS VCRSUM
Fig. 7 and 8—Turtle and alligator skull, lateral

Fig. 9-Alligator skull, ventral
Fig. 10—Turtle skull, ventral
6
2. LOWER JAW. Study figs. 11 and 12 and
dentify the named bones on your skeleton. A
>right light and a good hand lens may be needed
o reveal some of the suture joints between the
bones of the skull and of the jaw. Skulls from
young turtles should reveal suture joints better
than those from old turtles.
PREARTICULAR

\
ARTICULAR
/
Fig. 11—Turtle jaw (above,
medial; below, lateral).

Fig. 12—Alligator jaw. (above, medial; be-
low, lateral).
3. HYOID BONE. Normally found within the
nuscles of the tongue and neck, this bone de-
•ived from the second pharyngeal arch consists
)f an unpaired median body and two pairs of
jostero-laterally directed horns, the anterior and
:he posterior homs, fig. 13.
B. VERTEBRAL COLUMN AND RIBS, fig. 13.
1. CERVICAL VERTEBRAE. Eight verte-
irae are present in the neck. These can be with-
drawn beneath the carapace by the contraction
of powerful neck muscles to be described in
Chapter III. Observe the articulating processes
(zygapophyses) of these large vertebrae. Notice
the first cervical vertebra or atlas. It has little or
no body or centrum because this has been added
to the second vertebra, the axis, and forms the
odontoid process of the latter. The odontoid pro-
cess serves as a pivot about which the atlas may
turn from side to side. The remaining six cervical
HYOID BONES
LOWER JAW (MANDIBLE)
SKULL
ACROMIAL PROCESS
V
CERVICAL VERTEBRA (EIGHT)
HUMERUS
RADIUS
INTERMEDIN
CARPALS
PHALANGES

OBTURATOR FORAMEN
ISCHIUM
FIRST SACRAL VERTEBRA (TWO)
METATARSALS
PHALANGES
Fig. 13—Axial and appendicular skeletons, ventral
8
trtebrae are similar in structure and are typical
vertebrae in general.
2. DORSAL OR THORACIC VERTEBRAE.
in of these lie caudal to the cervicals. The dor-
1 vertebrae are firmly fused dorsally with the
^rtebral plates of the carapace. These verte-
ae consist of slender centra whose processes,
cept in the first, have been poorly developed,
le first dorsal vertebra exhibits strong lateral
ocesses curving abruptly ventrad to articulate
ith the eighth cervical vertebra.
3. RIBS. Each dorsal vertebra gives rise to a
a on each side. The ribs develop together with
c costal plates of the carapace with which they
se as thin bony ribbons which may reach lat-
ad as far as the marginal plates. Anteriorly
e ribs arise at right angles from the interverte-
al joints but posteriorly they arise from stubby
teral bases of the vertebrae and project postero-
terally from the centra. Some variation from
is pattern may be seen in different species of
rtles. Notice that the first pair of ribs, being
orter and smaller, fuses with the second pair,
short distance from vertebrae one and two of
e dorsal group.
4. SACRAL VERTEBRAE. Dorsal vertebrae
even and twelve are the sacral vertebrae and
e not fused with the carapace. The first ex-
hibits enlarged ribs, somewhat pyramidal in shape,
whose expanded distal ends are fused to the ilia
of the pelvic girdle.
5. CAUDAL VERTEBRAE. From twenty-
five to thirty caudal vertebrae generally are pres-
ent. Like the cervicals, the caudals are free from
the carapace and are moved, in life, by a number
of slender tail muscles. Caudal vertebrae four,
five, and six generally have longer rib-like pro-
cesses projecting from their centra at right angles.
On the first and seventh caudals these processes
are exceptionally short. On the remainder they
are further reduced or are entirely absent. Be-
ginning with the eighth caudal vertebra secondary
ventral processes, arising on the sides of the cen-
tra posteriorly, fuse at their tips to form a canal
through which the caudal artery and vein pass.
On the dorsal side each vertebra gives rise to a
pair of lateral articulating surfaces (zygapophyses).
Processes are reduced greatly or are lacking from
the most caudal tail vertebrae whose centra are
very slender.
APPENDICULAR SKELETON, figs. 13-15.
The pectoral girdle unites the forelimb, and the
pelvic girdle unites the hindlimb, to the axial
skeleton. These unions permit the turtle to bear
the weight of head, neck, trunk, and tail upon the
limbs when walking.

RIGHT
Fig. 14—Pectoral girdle, posterior
Fig. 15—Pelvic girdle, anterior
9
A. PECTORAL GIRDLE AND FORELIMR.
The pectoral girdle of turtles lies between the
carapace and the plastron and is attached via the
scapula to the vertebral column.
1. SCAPULA. The longest, straightest bone of
the pectoral girdle — also the most dorsal one.
It is united proximally by a small cartilage to
the first dorsal vertebra being attached at the
angle between the first dorsal vertebra and the
first rib. At the distal end of the scapula find the
acromial process (pre-coracoid) projecting anter-
iorly at right angles from the scapula.
2. CORACOID, the third part of the pectoral
girdle. It also lies at right angles to the scapula
but is not fused to it as is the acromial process.
The coracoids are joined by cartilage at their
medial margins. The distal end of each coracoid
is united by a ligament to the broad flattened
?nd of the acromial process.
3. GLENOID FOSSA. A cavity formed by
:he union of scapula, acromion, and coracoid. It
-eceives the head of the humerus to make the
;houlder joint.
4. HUMERUS, the bone of the arm. In addi-
:ion to its head note the two proximal tuberosities
separated by a groove, and the neck below the
bead, and the heavy curved shaft expanded dis-
tally for the articulation of the foreleg bones, the
radius and the ulna.
5. RADIUS, the smaller of the foreleg bones,
[t is about the same length as the ulna but is
more slender.
6. ULNA, the larger bone of the foreleg. De-
termine which of these bones, radius and ulna,
is medial and which is lateral in position.
7. CARPALS, the wrist bones as a group. Dis-
:ally the ulna articulates with two bones, a lateral
jlnare bearing a small knob on its side and a
Tiedially placed intermedian (intermediate) which
ies between the ends of the radius and ulna.
Distal to the radius is the radiale which may be
"used to the bone lying medial to it —the cen-
y.rcde.
8. CARPUS. A carpal bone appears at the
base of each metacarpal or bone of the forefoot
(hand or manus).
9. PHALANGES, the bones of the toes (digits).
There are two phalanges each in the first and fifth
toes. All the others have three phalanges apiece.
In each toe the distal phalanx bone forms a claw
which is capped with a horny covering.
B. PELVIC GIRDLE AND HINDLIMB. Like
the pectoral girdle, the pelvic, too, is composed
of three pairs of bones. These are more firmly
united than in the case of the pectoral girdle. The
pelvic girdle is also housed within the turtle "shell"
betwen the carapace and the plastron posteriorly.
1. ILIUM, the most dorsal bone of the pelvic
girdle. Each ilium serves to unite the pelvic
girdle to the vertebral column. Each is a stout
bone, flattened proximally where it fuses with the
pyramidal-shaped end of the first sacral rib on
either side of the first sacral vertebra.
2. PUBIS, antero-ventrally placed and medially
fused with its mate of the opposite side. The
pubes form a triangular horizontal shelf, the apex
of which is cartilaginous and is directed cephalad.
This portion is sometimes termed the epipubis.
Laterally each pubis exhibits a large pectineal
process for attachment of muscles. Postero-later-
ally each pubis is fused to an ilium as well as to
an ischium to form the acetabulum socket in which
the head of the femur articulates thus forming
the hip joint.
3. ISCHIUM, the third bone of the pelvic
girdle. The ischia also fuse together in the mid-
line and unite with the fused ilia anteriorly. On
either side of this union is a large round hole, the
obturator foramen. Each ischium exhibits a tub-
erosity projecting caudad. These processes are
for the attachment of muscles.
4. FEMUR, the thigh bone. It resembles the
humerus, having similar tuberosities and a some-
what larger head.
5. TIBIA AND FIBULA, the bones of the
leg. The stronger one is the tibia — its proximal
10
id is club-shaped but this is not true of the
3ula which is more slender throughout.
6. TARSALS, the ankle bones are six in num-
;r. Considerable fusion of more numerous em-
yonic bones has occurred here.
7. METATARSALS, the five bones of the foot
one for each digit.
8. PHALANGES, the bones of the digits. Like
those of the forelimb there are two each in the
first and fifth but three each for the other digits.
The distal phalanx of the little toe is very small,
being included within the web of the foot, there-
fore, there is no claw on the little toe.
11
CHAPTER III
Muscular System
The muscular system, as studied in anatomy,
includes only the somatic or striated skeletal
muscles. Heart muscle and visceral muscle be-
long largely to the circulatory and digestive sys-
tems respectively. The skeletal muscles of the
turtle have not been as thoroughly studied as have
those of some vertebrates, however, most muscles
presented in this chapter can be readily identi-
fied with the aid of the table of origins, inser-
tions, and functions together with the labeled
drawings. This method, it is believed, will per-
mit the identification and the learning of more
muscles in a given amount of time than is pos-
sible with the ordinary style of laboratory manual.
The student should be prepared to pass one or
more oral examinations on his dissection of this
system.
STRUCTURE OF A TYPICAL MUSCLE.
Most of the named muscles of the body wall
(soma) consist of more or less spindle-shaped
bundles of microscopic fibrils. These bundles
have a thicker middle portion, the belly, and two
rather slender ends, one of which, the origin is
more or less immovable and the other, the in-
sertion which is more or less movable. White
glistening tendons generally attach a muscle at
each of its ends to a bone or to a ligament. Liga-
ments hold bones together, their fibers blending
securely with the fibrous periosteum which covers
the bones. Since tendons generally attach muscles
to bones their fibers blend with the periosteum
at one end and with the muscle fibers at the other.
Along their sides adjacent muscles are held to-
gether by connective tissue or intermuscular fascia.
Subcutaneous fascia unites superficial muscles
with the overlying skin. Broad sheets of con-
nective tissue covering flat muscles such as the
Dblique and transverse abdominals, in most high-
er vertebrates, are termed aponeuroses. These
muscles are not very evident in turtles owing to
their being firmly attached to the plastron.
Care must be exercised in "dissecting" muscles
for one must avoid cutting them but rather they
must be separated by tearing away the inter-
muscular fascia by means of the back side of a
scalpel blade, the scalpel handle, or a strong probe
or seeker. Every muscle identified should be
thus fully separated from its fellows and its origin
and insertion identified by means of the tables
and diagrams. Be sure to break away the cara-
pace wherever it interferes with your progress.
If at any time it becomes necessary to cut or
to remove a muscle in order to identify others be-
neath it, you should cut across the belly of the
muscle so that it can later be studied by merely
bringing together the cut ends.
PREPARATION OF THE TURTLE FOR
THE STUDY OF MUSCLES.
The muscles of the head, neck, limbs, and tail
can readily be exposed merely by skinning these
parts. In order to study the more proximal limb,
neck, and tail muscles, however, as well as those
of the trunk it will be necessary to remove the
plastron. If this has not been previously done
you must cut through each of the bridges uniting
the carapace and plastron. Next cut through the
skin where it joins the plastron and the latter
can now be easily removed. A bone saw, hack
saw blade, or strong bone shears will suffice for
this job of bone cutting. CAUTION: The muscles
adhering to the dorsal side of the plastron should
be cut off close to the plastron in this case.
IDENTIFICATION OF MUSCLES.
Rather than reading a detailed description of
each muscle it will be possible to save much time
12
referring to the tables of the muscles given
low. These may be used in connection with
5 illustrations so that the origin, insertion, and
action of each muscle may be learned as it is
identified. Figs. 16-20.
GENIOHYOID
HYOGLOSSUS
BRANCHIOHYOID
STERNOHYOID
OMOHYOID
TdACHEA
DELTOID
MYLOHYOID (INTERMANOIBULARIS)
LIGAMENT
SUBSCAPULARS
BICEPS BRACHil
CORACOID
SERRATUS MAGNUS
FLEXOR CAUDAE LUMBALIS
TRANSVERSE ABDOMINIS
INTERNAL ILIAC -
IICEPS FEMORIS ADDUCTOR
GRACILIS
DILATATOR CLOACAE
FEMUR
ENSOR DIGITORUM LONGUS
GASTROCNEMIUS

EXT RADIUS LONGUS DELTOID
INTERNAL BRACHIAL
EXTERNAL RADIUS BREVIS
EXTERNAL ULNAR
EXTENSOR DIGITORUM
BICEPS BRACHiI
SUPRASCAPULARIS
SERRATUS MAGNUS
CLAVICULOBRACHIALIS
LATISSIMUS DORSI
ELEXOR CAUDAE LUMBALIS
EPIPUBIS
ATTRAHENS PELVIM
INTERNAL ILIAC
OBLIQUE ABDOMINIS
PECTINEAL PROCESS
RETRAHENS PELVIM
ISCHIUM
SARTORIUS
SEMIMEMBRANOSUS
SEMITENOINOSUS
FLEXOR CAUDAE LATERALIS
PL ANTARIS
ANTERIOR TIBIALIS

Fig. 16—Muscles, ventral
Fig. 17—Muscles, lateral
13
LONGUS COLLI
LATISSIMUS DORSI
CLAVICULO BRACHIALIS
TRICEPS BRACHII
PLANTARIS
SUPRASCAPULARIS
BICEPS BRACHII
CORACOID

FLEXOR CAUDAE LUMBALIS
INTERNAL ILIAC
PSOAS
RECTUS FEMORIS
SARTORIUS
ANTERIOR TIBIALIS
EXTENSOR DIGITORUM LONGUS
PERONEUS
GASTROCNEMIUS
AODUCENS PELVIM
SACRAL VERTEBRA ABDUCENS PELVIM
FLEXOR CAUDAE LATERALIS
GLUTEUS
SEMIMEMBRANOSUS
SEMITENDINOSUS
Fig. 18—Pelvic and pectoral muscles, ventral
14

S
15
1AJBLE 1. SKELETAL MUSCLES OF THE TURTLE
MUSCLE
ORIGIN
INSERTION
ACTION
HEAD AND NECK MUSCLES
Temporal
'Digastric
Cervico-capitis
Stemomastoid
Omohyoid
Latissimus colli
Longus colli
'Retrahens capitis collique
Longissimus dorsi
Transverse cervical
Biventer cervical
Spinal cervical
Obliquus transversalis colli
Supratemporal fascia
Ventral side of bulla
Ant. cervical vertebrae
Ligament at tip of post-
erior hyoid
• Anterior margin of cora-
coid
Sides of cervical verte-
brae
Cervical vertebrae
> Cervical vertebrae and
roof of mouth
Vertebral column dorsal
to ribs
First cervical vertebrae
Middle cervical verte-
brae
Last cervical vertebrae
Cervical vertebrae
Between rami of jaws
Ventral ramus of jaw
Posterior tip of bulla
Base of skull
Edge of ant. hyoid
With mate on midven-
tral line
Cervical vertebrae
Carapace ant. to ilium,
and dorsal vertebrae
Posterior cervical verte-
brae
Posterior cervical verte-
brae
Fascia over skull and
temporal muscle
Middle cervical'
brae
Cervical vertebrae
Elevates jaw (closes mouth)
Depresses jaw (opens mouth)
Turns head (side-to-side)
Turns head, supports pectoral girdle
Helps depress jaw. retract head, and
lower oral floor
Compresses throat as in swallowing
Extension of neck
Retraction of head and neck
Extension of neck
Arches neck (flexion)
Elevation of head
Extends and elevates neck
Twists and extends neck
PECTORAL GIRDLE AND FORELIMB MUSCLES
Pectoralis major
Deltoid
Suprascapularis
Biceps brachii
Triceps brachii
Internal brachial
External radius b re vis
External ulnar
External radius longus
Extensor digitorum
Serratus magnus
Palmaris
Suprascapularis
Claviculobrachialis
Latissimus dorsi
Precoracoid, distally and
plastron
Anterior margin of plas-
tron fir precoracoid
ventrally
Coracoid, ventrally
Posterior margin of
coracoid
Head of humerus fir
periosteum over scap-
ulo-precoracoid joint
Head of humerous
Humerus, distally
Humerus, distally
Alongside humerus and
radius
Humerus, distally
Carapace, anteriorly and
";e of bridge
I end of humerus
Coracoid, dorsally
Along scapula
Carapace, ventrally and
along scapula
Head of humerus
Suprascapularis muscle
anteriorly Ac head of
humerus
Head of humerus
Radius and ulna
Ulna
Radius and ulna
Carpels
Carpels
Carpal and phalanx of
first digit
Metacarpals fir phalanges
Coracoid
Broad ligament continu-
ing as phalangeal
fascia
Head of humerus and
claviculobrachialis
Head of humerus
Neck of humerus via a
broad ligament
Adduction of humerus posteriorly
Anterior and lateral extension of arm
Flexion of arm
Forearm flexion fir adduction
Extension fir rotation of forearm
Forearm flexion
Extends and rotates hand outwards
Extends and rotates hand outwards
Extension of hand
Extension of hand
Anterolateral extension of shoulder or
foreleg
Flexion of hand fir digits
Posterior adduction and flexion of arm
Ventrolateral extension of arm
Lifts arm dorsally fir anteriorly


Will
irsskunoN
Attrahens pelvim
Oblique abdominis i/fhese
Transverse abdom. J
Triceps femoris adductor
Internal iliac
Flexor caudae lumbalis
Flexor caudae lateralis
Dilator cloacae
Sphincter cloacae
Retrahens pelvim
Adducens pelvim
Abducens pelvim
Sartorius
Semimembranosus
Semitendinosus
Gracilis
Anterior tibialis
Plantaris
Gluteus
Vastus internus
Rectus femoris
Gastrocnemius
Peroneus
Extensor digitorum longus
Crureus
Semimembranosus
Psoas
MUSCLES OF PELVIC REGION
Pectineal or lateral pubic , Plastron, posteriorly
process
are mostly removed along with the plastron to which they are attached)
Proximal head of femur
Pubis, ventrally & isch-
ium
Dorsal surface, margin
it apex of pubis
Periosteum above thor-
acic vertebrae 2/3
way back from neck
Head of ilium & cara-
pace
Distal to head on femur
Ventral tail fascia
Tail, mid-dorsally
SKELETAL MUSCLES CONTINUED
Sacral vertebrae it along
tail
Sacral vertebrae & along
tail
Lateral pubic process
and pelvic ligament
Carapace near anterior
head of ilium
same as above
Tail, midventrally fit
anal skin
Tail, midventrally 6t
anal skin
Plastron, posteriorly
Anterior head of ilium
same as above
HINDLIMB MUSCLES
Via tendon to pelvic
ligament
Posterior border of isch-
ium it pelvic ligament
Proximal end of ilium
Pelvic ligament via a
long slender tendon
Head it body of tibia
Femur
Head of femur along
edge of ilium & sacral
vertebrae
Lateral pubic process
& margin of femur
On ilium via a tendon
Distal end of femur
On body of fibula
Distal end of femur
Head of femur
Proximal end of tibia
Multiple insertions on
tibia
Body of fibula
Proximal head of tibia,
along inner surface
First metacarpal it other
small insertions
By broad fascia over
plantar area it by ten-
dons to phalanges
Head of femur
On tibia with sartorius
Metatarsus of last digit
Metatarsus of last digit
Metatarsus of 4th it pha-
lanx of 5th digits
Metatarsus
Head of tibia with sar-
torius
SKELETAL MUSCLES CONCLUDED
Head of ilium it caudal
vertebrae
Ilium & sacral vertebrae
Ligaments of semimen-
branosus
Head of femur, ventrally
Fixation of pelvic girdle
Extends thigh
Flexes leg
Pulls in tail
Lateral flexion of tail
Retracts it rotates tail
Retracts it rotates tail
Fixation of pelvic girdle
Anchors pelvic g'rdle to carapace
same as above
Extension of leg
Flexes leg
Flexes leg
Flexion it slight rotation of leg
Pulls foot towards body as in walking
Retracts claws, extends foot, flexes leg
Pulls leg forward ic dorsally. Helps
retract leg.
Aids sartorius in extension of leg
Leg extension
Pulls foot to body, spreads claws, tc
helps pull leg posteriori)'
Spreads claws it pulls them posteriorly
Pulls claws together it lifts it extends
toes
Leg extension
Flexes leg
Pulls leg under carapace
CHAPTER IV
Digestive and Respiratory System
If by chance the muscular system has been
)mitted, then the plastron will now need to be
emoved. If the bony bridges joining plastron
o carapace have not been previously cut, this
hould be done now as directed in the foregoing
hapter.
l. PERITONEUM AND COELOM.
1. Parietal peritoneum, a tough thin membrane
overing all visceral organs and forming an inner
ning for the plastron and carapace, where they
irround the visceral cavities. Muscle layers are
bsent or much reduced in the ventral body wall
nee the plastron fully supports this region in
tost turtles. The muscles of the girdles and limbs
-e present as usual.
2. Pericardial sac, a triangular sac continuous
ith the parietal peritoneum in the ventral mid-
le just posterior to the pectoral girdle. This
c encloses the heart and is termed the parietal
zricardium while the thin outer covering of the
;art itself is the visceral pericardium.
3. Pericardial cavity, a portion of the original
>elom lying between the parietal and visceral
yers of the pericardium and surrounding the
:art. Remove the ventral portion of the parietal
•ricardium thus exposing the heart but preserve
e dorsal portion of the sac for future reference.
4. Ventral abdominal veins. These large ves-
ts form a letter H-shaped design in the ven-
il peritoneum. Their posterior limbs arise from
e pelvic girdle and their anterior limbs enter
b right and left liver lobes, respectively. A
anch from each anterior limb extends antero-
erally to the pectoral girdle on its own side. A
jss anastomosis (transverse abdominal vein) will
noted midway between the apex of the pelvic
girdle and the posterior borders of the liver lobes.
Cut away the ventral peritoneum but leave the
vessels intact. Now cut both ventral abdominals
just posterior to the cross anastomosis and reflect
the anterior limbs forward so that the abdominal
viscera may be clearly seen.
5. Pleuroperitoneal cavity, the space exposed
by removing the ventral parietal peritoneum. This
space includes most of the visceral organs.
6. Coelom, the pericardial and the pleuroperi-
toneal cavities.
B. VISCERA AND MESENTERIES,
figs. 21 and 22.
Break away the sides of the carapace (use bone
shears or pliers) between the fore and hind legs
to facilitate viewing the viscera. Various masses
of yellowish-green fat and more peritoneum may
be removed. The form, color, and relationships
of the following organs should be learned.
1. Liver, a brown gland — the largest in the
body. Its left lobe nearly covers the stomach and
extends to the right, dorsal to the ventricle of
the heart. It expands into the right and largest
lobe which covers part of the small and large in-
testines. An extension of. the left lobe lies dorsal-
ly in the lesser curvature of the stomach. If the
specimen is a female, ovaries containing eggs of
various sizes and of spherical shape will be seen
lying just posterior to the liver and against the
dorsal body wall.
2. Hepatic mesenteries, in which the anterior
limbs of the ventral abdominal veins are con-
tained, are short mesenteries uniting the right and
left liver lobes to the ventral peritoneum. These
mesenteries correspond to the falciform ligament
seen in most vertebrates.
18
3

Fig. 22—Digestive system, ventral
19
3. Transverse septum, a membrane formed of
he parietal peritoneum dorsally and of the under-
ying dorsal wall of the pericardium. It lies in an
>blique plane owing to the more caudal position
»f the heart in turtles (the heart lies farther an-
erior in fishes and in amphibians).
4. Coronary ligament, an attachment of the
iver to the transverse septum. Follow the parietal
>eritoneum as far anteriorly as possible and ob-
;erve its continuity with the dorsal portion which
orms the inner lining of the carapace. Note also
he connections between the ventral and dorsal
)eritoneum in the region of the pelvic girdle.
5. Esophagus (gullet), a slender tube uniting
he pharynx with the stomach. It may be seen
n part by lifting the left liver lobe far over to the
ight. It joins the stomach at a point just dorsal
o the left atrium of the heart.
6. Stomach, a curved tubular digestive organ
eading into the small intestine. The stomach is
nach greater in diameter than either the esopha-
gus or the intestine.
7. Gastrohepatic ligament, a short mesentery
ittaching the stomach all along its lesser curva-
ure to the left lobe of the liver.
8. Duodenum, the first part of the small intes-
tine. It begins where the stomach ends just dor-
sal to the bridge of liver which connects the left
ind right liver lobes.
9. Hepatoduodenal ligament, a mesentery unit-
ng the duodenum with the right hepatic lobe along
the middle of its dorsal surface.
10. Pancreas, a long slender pale gland lying
ilong the duodenum at the attachment of the
hepatoduodenal ligament.
11. Pancreatic duct. This is fairly stout and
passes from the pancreas into the duodenum about
ane half centimeter from the right end of the
pancreas. Tease away the pancreas at this point
and identify this duct.
12. Gall bladder, the bile reservoir. It is
greenish colored and lies on the dorsal side of the
right liver lobe near its right border.
13. Bile duct (ductus choledochus), a short
stout duct which empties the gall bladder into
the duodenum. It can be easily identified and
traced to its termination.
14. Small intestine proper, that part of the small
intestine beyond the duodenum, beginning at the
sharp curve posterior to the right border of the
right liver lobe. It forms several coils and termin-
ates by empting into the beginning of the large
intestine, the caecum. The right ovary may now
be removed, if necessary, to facilitate tracing the
small intestine.
15. Dorsal mesentery (mesentery proper). This
attaches the intestine to the dorsal midline of
the body cavity. Lift the intestine enough to
demonstrate this mesentery.
16. Mesoduodenum. This is fused to the hepa-
toduodenal ligament so that the two are indis-
tinguishable. Both of these structures are mesen-
teries.
17. Mesogaster, a separate mesentery distin-
guishable from the gastrohepatic ligament. It
connects the greater curvature of the stomach
with the dorsal midline of the body cavity.
18. Colon, the large intestine. Trace the small
intestine to its junction with the caecum (begin-
ning of large intestine) located in the posterior
right quadrant of the visceral cavity.
19. Mesocolon, the mesentery of the colon.
20. Cloaca, the terminal portion of the alimen-
tary canal. It opens to the exterior via the anus.
Cut out the anterior mid-portion of the pelvic
girdle, using bone shears, and trace the colon,
noting its ascending transverse, and descending
limbs, to the cloaca. The transverse colon will be
found to be fused to the mesogaster. A thin-
walled bilobed urinary bladder will be seen just
dorsal to the pelvic girdle.
21. Spleen, a spheroid vascular gland whose
functions include destruction of old red blood
cells, salvaging hemoglobin, the manufacture of
certain kinds of white blood cells, and other
specialized duties. It lies in the mesocolon just
anterior to the caecum but is dorsal in position,
hence careful search in the mesocolon may be
required in order to find it.*
ORAL CAVITY AND PHARYNX, fig. 23.
Force open the jaws and cut the soft tissue
ck through the angles of the jaws until the
mth can be opened enough to see the beginning
the esophagus. A probe can now be passed
rough the entire esophagus into the stomach.
Fting the stomach over toward the right side
11 facilitate passage of the probe.
1. Oral (buccal) cavity, the space enclosed by
j jaws. Note the horny beaks which cover the
vs. Observe the relationship between this horn
d the skin of the nostril, face, and neck.
2. Beak. True teeth are lacking in turtles but
the horny beaks extend into the mouth and de-
velop tooth-like ridges paralleling the edges of
the beaks. Compare these for upper and lower
jaws.
3. Anterior nares (nostrils), two small open-
ings in the tip of the snout. These lead back
through the nasal passages which open on the
roof of the mouth as the:
4. Posterior nares. These "can best be found
by passing a slender probe back through the nos-
trils and nasal passages where their openings will
UPPER JAW
YE
IASSETER MUSCLE
NGLE of JAW
EXTERNAL NARES
POSTERIOR NARES

SOPHAGUS
OPENING of EUSTACHIAN TUBE
PHARYNX
A.RYNGEAL PROMINENCE
DNGUE
GLOTTIS
BEAK
LOWER JAW
Fig. 23—Mouth and Pharynx
21
>e seen just posterior to the bony plate of the
lpper beak and in a depression bounded antero-
aterally by a Y-shaped ridge of soft tissue.
5. Tongue, a triangular papillated fleshy struc-
ure in the floor, of the buccal cavity which is
irmly attached along its entire length.
6. Pharynx, a cavity extending from the pos-
erior border of the tongue (its base) to the be-
ginning of the esophagus.
7. Laryngeal elevation or prominence, a raised
sortion of the floor of the pharynx just behind
he base of the tongue.
S. Glottis, a slit-like opening in the center of
he laryngeal elevation. It opens into the simple
arynx.
9. Auditory (Eustachian) tube, a small canal
eading from the roof of the pharynx to the middle
?ar cavity. Both tube and cavity are derivatives
)f the first pharyngeal pouch. (The openings
nto the auditory tube may have been damaged
when cutting back through the angles of the
aws.) Find the slit-like opening of one of these
:ubes and probe it to the cavity of the middle
jar. A disc of skin (tympanum) covering this
javity may thus be identified. Cut away this
lisc and view the cavity beneath it.
D. RESPIRATORY DUCTS AND LUNGS, figs.
24 and 25.
1. Larynx. The upper end of the respiratory
luct. It leads into the trachea telow and opens
ibove into the pharynx via the glottis. Find a
pair of arytenoid cartilages, one on either side ot
the larynx. These support wedge-shaped flaps
on either side of the glottis and serve to regulate
the size of this opening. A ring-shaped cricoid
cartilage lies posterior to the glottis. It is wide
ventrally but narrow dorsally.
2. Trachea, a connection of the larynx with the
bronchial tubes which enter the lungs.. Slit open
the glottis and anterior part of the trachea along
the mid-ventral line and notice that the glottis
opens into a spheroid chamber anterior to the
first cartilaginous ring of the trachea — this is the
cavity of the larynx. Now slit open the skin of
the neck along the ventral midline. Spread the
skin and muscles apart and trace the trachea to
its bifurcation into the right and left bronchi.
3. Bronchus, a branch formed by the bifurca-
tion of the trachea. There are two main branches,
a right and a left. With a curved flexible probe
follow the left bronchus as far as you can. Re-
flect the stomach and large intestine to the right,
open the peritoneum over your probe and note the
lungs.
4. Lungs, reddish spongy respiratory organs
lying against the carapace on each side just pos-
terior to the pectoral girdle. Open the left lung
by a lateral incision passing to the left from your
probe. Study the texture of the lung, observing
its air pockets or alveoli and the tough connective
tissue strands which separate them. Note the
relationship between peritoneum and lung in both
its anterior and posterior regions. Is the lung en-
tirely retroperitoneal or does part of it extend into
the pleuroperitoneal cavity?
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