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ALBERT R. MANN
LIBRARY
New YorK STATE COLLEGES
OF
AGRICULTURE AND HomME ECONOMICS
AT
CORNELL UNIVERSITY
ornell University Libra
course of instruction in zootomy. (Ver
A COURSE OF INSTRUCTION
IN
ZOOTOMY
(VERTEBRATA.)
A COURSE OF INSTRUCTION
ZOOTOMY.
(FTERTEBRATA.)
BY
T. JEFFERY PARKER, B.Sc. LonpD.
x
PROFESSOR OF BIOLOGY IN THE UNIVERSITY OF OTAGO, NEW ZEALAND.
WITH SEVENTY-FOUR ILLUSTRATIONS.
London :
MACMILLAN AND CO.
1884.
The Right of Translation and Reproduction is reserved.
cs
Ot F772
pas
ofa, Ore
R. Cray, Sons, anD TAYLOR,
BREAD STREET AILL, © G.
TO
MY FRIEND AND CRITIC,
C By Be Pe
¥ Dedicate this Book.
PREPACE,
THE directions for the dissection of certain vertebrate
animals of which the present book consists were begun
many years ago when I was privileged to act as demon-
strator to Professor Huxley, at the Royal School of Mines,
South Kensington. They. are drawn up on much the same
plan as the “ Laboratory Work,” in Professors Huxley and
Martin’s Llementary Biology, and aim at being a continuation
of the zoological part of that work, in much the same way
as the Practical Phystology of Dr. Foster and Mr. Langley
may be said to continue it on the physiological side.
It must be borne in mind that the book is merely a “Course
of Instruction,” in the dissection of Vertebrates, and that it
makes no pretence whatever at giving a complete account
of the anatomy of the types selected. The time at the
disposal of the average student of Comparative Anatomy is
so short, that for him to examine half a dozen vertebrate
animals—to say nothing of Invertebrates—in the same detail
as the student of Human Anatomy examines his single type,
would be quite out of the question even if it were necessary.
On the other hand, it is of the first importance that he should
viii PREFACE.
not only be made familiar with the essentials of vertebrate
organisation, but should be so drilled in details as to be
capable of working out, with some degree of thoroughness,
any ordinary vertebrate animal which may be set before
him.
The advantage of the study of Comparative over that of
Human Anatomy lies in the fact that in the former the dry
facts are, to borrow an expression of Dr. Michael Foster’s,
“salted with the salt of morphological ideas.” But if the
same thoroughness in practical work is not demanded of
the student of Animal Morphology as of the medical student,
if he is allowed to shirk the discipline of laborious dissection,
and to be content with a “general notion” of the structure
of the types he examines, he runs a very serious risk of
getting uncommonly little meat to his salt, and of losing
in depth what he gains in breadth.
It was therefore necessary to decide how much might be
left out without leading the student into a superficial way
of working ; and in striving to “keep the mean between the
two extremes of too much stiffness in refusing and of too
much easiness in allowing” any omissions, I am only too
well aware how largely the personal equation enters into
questions of this sort, and how unsatisfactory the
compromise I have decided upon may seem to other
teachers.
The subjects described are mostly such as can be readily
obtained at any time of the year. The Skate is chosen in
preference to the more typical Dogfish, partly because it is
PREFACE. ix
a regular market commodity, partly because it is, to my
mind, quite unrivalled for the study of the vertebrate nervous
system. The Rabbit is chosen in preference to the Dog or
Cat—either of which, and especially the former, would have
been preferable for some reasons—because it can be more
readily obtained in quantity; its size, moreover, makes it
more suitable than the Rat. The Green Lizard and the
Lamprey cannot always be depended on, but, as they can
both be easily preserved whole in alcohol, this is of less
consequence than in the other cases. It was not thought
necessary to include an amphibian, since the Frog is fully
described in the Zvementary Biology.
The labour of correcting the proofs and of superintending
the drawing on wood and engraving of the illustrations has
fallen upon my brother, Mr. W. N. Parker, F.Z.S., without
whose help the publication would have been almost out of
the question. Besides the editorial work, he has made out
several points in the anatomy of the Cod and Lizard,
which, owing to lack of material, I was unable to decide
myself. Many important omissions and some actual errors
have thus been avoided.
I am indebted to Professor Huxley for having kindly read
over such parts of the work as were written when I left
England, and for valuable suggestions thereon. But beyond
this, I shall always feel that any value the book may possess
is very largely due to the example set me by Professor Huxley
during all the years I had the good fortune to be associated
with him.
x PREFACE.
My friend and former colleague, Mr. G. B. Howes,
rendered me much assistance in preparing and correcting
those parts of the directions which were drawn up in
England, and has also given considerable aid to my brother
in working out some doubtful points which arose while the
work was passing through the press.
I am further indebted to Mr. Howes for the drawing
for Fig. 34, and to my brother for Fig. 32. Figs. 35, 36,
and 37 are copied from my father’s monograph on the
Lizard’s skull (P42. Trans. 1879), and Fig. 38 from
Llerpetologia Europea ; the remaining illustrations are from
my own drawings. The whole of them have been drawn on
the wood by Mr. Coombs, and engraved by Mr. Cooper:
judging from the few proofs which have so far reached
me, I have every reason to be grateful to those gentlemen
for the care and skill with which their work has been
done.
ne aes
Oraco UNIVERSITY Museum,
DuNEDIN, N.Z.
Fune, 1883.
CONTENTS.
PAGE
PREFACE . : vii
List oF Woopcurs A xiii
INTRODUCTION. . xvii
THE LAMPREY—
A. The Skeleton . I
B. Directions for Dissection F 8
THE SKATE—
A. The Skeleton . é 2 27
B. Directions for Dissection a o> oy ot 40
C. Special Dissection of the Nervous System and Sense
Organs , . 69
THE Cop—
A. The Skeleton . i ue 3 : . 86
B. Directions for Dissection 101
THE LizAaRD—
A. The Skeleton oe s 4 + 130
B, Directions for Dissection . . : 4 153
xii CONTENTS.
THE Picron—. PAGE
A. The Skeleton . ; eo = TS2
B. Directions for Dissection 209
Tue RasBir—
A, The Skeleton 262
B. Directions for Dissection 286
Works OF REFERENCE 381
INDEX . ee. ee. A Ow OG 384
Co ge
Pep ns
LIST OF WOODCUTS.
Petromyzon marinus. The skull, from the left side... .
The brain-case, from above ... ...,..
The nasalcapsule ....... 2.2.2,
Dissection of the anterior part of the body, from ‘ihe
leftsidé: 04 4 a8 ae Ra oe ae
The urinogenital sinus and adjacent parts
Transverse section through the branchial region. .
Transverse section through the abdominal region . .
Transverse section through the caudal region
‘The braim, from above « 4 + = « & » & x
Raja nasuta. The skeleton, from beneath. . .. .
Part of the vertebral column ste tea
A trunk vertebra, from the front
Longitudinal section of trunk vertebra
A caudal vertebra, fromthe front. .......
The gall-bladder and bile-ducts .. «......
The portal vein ...... :
The venous system... - +e - ee ee ee
Raja batis. Urinogenital organs (male). »
Urinogenital organs (female) . .
Raja nasuta, The arterial system ...... —
Diagram of the heart and chief blood-vessels . . .
The nervous system, from above ee 5
Raja batis. The brain, from beneath... .....
Longitudinal section of the brain...
The brain, from the leftside. .--- 1... -
Raja nasuta. Roots of the fifth, seventh, and eighth nerves
‘
xiv LIST OF WOODCUTSs.
FIG, PAGE
27. Raja nasuta. Principal branches of the fifth, seventh, and
eighth nerves ... Reo oR Se ae, ANS:
28. Raya batis. The auditory agen ‘ ee
29. Gadus morrhua. Side view of a di: artioulned skull . 92
30. The superficial muscles and nerves : 104
Br. ‘The alimentary canal . 108
32. The vascular system. : . 17
33- The auditory organ... 123
34. ‘The brain « . 2 + « i ae : 125
35. Lacerta agilis. Longitudinal section of the skull ‘ 137
36. The columella auris . . 142
37. The chondrocranium, from abave . 144
Lacerta wees Outline of the head in the three species,
i Weal showing the epidermic scales 155
Zootoca vivipara.
39. Lacerta viridis. Muscles of the trunk, ventral aspect . . . 157
40. Dissection from the ventral aspect, showing the alimen-
tary canal and vascular system. . 1€0
4l. Urinogenital organs (male) . : . a 4% © N60
42. Urinogenital organs (female) . 167
43. The heart, dorsal aspect . a «172
44. The aortic arches. . s a 373
45- The brain . 3 : 177
46. Columba livia. Sacrum of a young individual 187
47- Skull of a young individual 189
48. The columella auris . 195
49. Manus of a young individual 203
50. Pelvis of a young individual . 204
sl. Tarso-metatarsus of an unhatched embryo 207
2 Urinogenital organs (male) 228
53- Urinogenital organs (female)... 230
54. The circulatory system bs 232
55. ‘The cloaca . 236
56. The heart, from the dorsal diet. 2 241
ve The lungs and syrinx - 245
58. The brain < 255
59. Dissections of the brain . - Pe 259
60. Lepus cuniculus. Part of the alimentary canal w ih the
portal system and bile-ducts . 301
61. The vascular system do ox 309
62. Urinogenital organs (male aasil female), oni the side 317
LIST OF WOODCUTS.
Lepus cuniculus. Part of the female organs, ventral aspect .
Longitudinal section of the head
Muscles of the fore limb—
A. From the outer side
B. From the ventral aspect
C. From the inner side
Muscles of the manus . . ho
Muscles of the hind limb, inner side .
Muscles of the hind limb, outer side .
Muscles of the pes
The brain, from beneath .
Dissections of the brain, from above .
Longitudinal section of the brain .
XV
PAGE
322
334
340
341
342
347
352
355
361
367
371
378
INTRODUCTION.
DISSECTION is best performed at a strong deal table, not
less than three feet long by two feet wide: it should, if
possible, be placed at a window, so that the operator faces
the light, otherwise the more delicate work will be hindered
by the shadows of the hands and instruments.
In nearly every case the subject should be firmly fastened
down during dissection, either to the table, or, better, to a
soft deal board, about one foot and a half long by one foot
wide, with a narrow bead tacked round the edge so as to
convert it into a shallow tray: the advantages of this are
that the subject may be turned in any direction without
unfastening, and that the edge confines the mess caused by
escape of blood, &c., to a limited area. The best fastenings
are small awls fixed into wooden handles, about an inch
long, and just thick enough to be conveniently grasped:
these can be more easily driven into the wood than large
pins, are not so liable to bend, and hold more firmly.
Care must of course be taken to thrust them through some
b
xviii INTRODUCTION.
part—e.g. skin—the slight injury to which will not interfere
with the dissection.
The more delicate dissections are best conducted under
water. A convenient dissecting dish is made by fitting a
piece of sheet cork weighted with one of sheet lead into
the bottom of a common pie-dish: the sloping sides of this
latter are admirably adapted for admitting the greatest
possible amount of light. The subject, in this case, is fixed
out with small pins.
The most necessary dissecting instruments are :—
Three or four scalpels of various sizes.
A large and a small pair of scissors.
A large and a small pair of forceps.
A pair of bone-forceps.
A “seeker,” ze. a blunt bent needle fixed in a handle.
A German silver anatomical blowpipe.?
The ordinary pointed form of scalpel is the best, those
with obliquely truncated ends are rarely suitable. The
scissors should have sharp points, and should bite well to
the very end: this is especially important with the small
pair, which will otherwise be perfectly useless. The forceps,
also, should meet accurately at the points, which should be
roughened so as to insure a firm grip; in the small pair the
pin placed to prevent the points crossing when pressure is
applied, should fit easily but not loosely in the hole for its
1 Boxes containing the above set of instruments are made by
J. Weiss & Son, 62, Strand ; Hawkesley & Son, 300, Oxford Street ;
Cc. Baker & Co., 244, High Holborn; J. Swift, 81, Tottenham Court
Road ; and J. B. Medland, 12, Boro’ High Street.
INTRODUCTION. xix
reception ; if the latter is too large the points will always be
liable to cross.
The bone-forceps should have straight blades, and the
handle should be sufficiently wide apart to admit of their
being conveniently worked without obstruction by the fingers.
. They are used for cutting through bones ; for instance, those
of the skull in the removal of the brain.
The seeker is useful both as a probe and for clearing away
. . the connective tissue from blood-vessels, nerves, &c., without
danger of cutting them.
All the instruments should be of the best steel; it is false
economy to buy inferior ones, as they lose their edge very
quickly and require constant sharpening.
A useful addition to the above is a common butcher’s
knife for rough work, e.g. for cutting through the skin of the
skate, the asperities of which completely spoil a scalpel. For
fine dissection spring scissors are very useful, but are by no
means indispensable.
Directions for injecting blood-vessels are given on pp.
48, 111, 162, 218, and 298: to these I may add that a
very convenient fluid injection for fine vessels is made by
straining through muslin a strong solution of gum-arabic in
water coloured with precipitated Prussian blue or carmine :
after injection the subject is placed in alcohol, which
coagulates the gum. This has the double advantage over
gelatine (p. 162) that it is used cold and that it keeps better
_ in alcohol.
Injecting syringes provided with brass cannulz of various
xX INTRODUCTION.
sizes are to be had from the instrument-makers. But a
common brass ear-syringe holding about two ounces answers
every purpose, using for cannula glass tubes of the form
shown on p. 48, adapted to the nozzle of the syringe with
short pieces of caoutchouc tubing. ‘ Bull-dog”’ forceps will
be found very useful in injecting for clamping any vessels
which may have been accidentally cut.
In large classes where the time of the student is limited,
it is usually inconvenient for each one to inject his subject:
it is then desirable to have an injected preparation in the
room which may be consulted when necessary. For this
‘ purpose, a rough dissection which the students are allowed
to handle is far more useful than a more elaborate preparation
mounted in a bottle. In fact, one may say that the only
alcoholic preparations of real use to beginners are those
which are simple enough to tell their own tale almost at a
glance. The most important, in my opinion, are :—
a. Preparations of the heart with the origins of the great
vessels, either filled with solid injection, or distended with
alcohol, the cavities, in the latter case, being cut open.
b. Preparations of the entire brain with the origins of the
nerves, and various dissections of the same organ.
¢. Preparations of the adult urinogenital organs, with the
various accessory glands, ducts, apertures, &c., displayed.
Many other very useful preparations might be mentioned,
but the above, as demonstrating important points about which
the beginner is certain to experience considerable difficulty,
may be considered as the most essential.
INTRODUCTION. xxi
As the hearts and brains of most of the subjects selected
are small, similar preparations from larger types are very
valuable for demonstration ; for instance, the monitor or
iguana, the goose or turkey, and the dog, sheep, or even
horse. It will, of course, be all the better if some of. these
structures—especially a larger mammalian brain than the
Rabbit’s—can be dissected by the students themselves as
supplementary subjects.
Dissections of large hearts for demonstration may be
prepared by the glycerine jelly process described on p.
2;1 the various structures are more readily pointed out on
such preparations than on those kept in alcohol: they may
be made still clearer by colouring the different parts.
The larger brains are best prepared by Giacomini’s
method : the organ is placed in a saturated solution of zinc
chloride, and then, after removal of the pia mater, in strong
alcohol, which should be renewed at least once. When
thoroughly hardened it is transferred to strong glycerine, and
retained therein until thoroughly permeated : this is shown
by its sinking in the fluid. The brain is then removed from
the glycerine, drained thoroughly, and, after a time, sized and
varnished. Any dissections which may be required are made
before placing in glycerine.
1 Since writing that description I find that the objects should be
well hardened in alcohol before being placed in the glycerine fluid ;
that it is best to substitute 0-05 parts of a concentrated solution” of
phenol for the corrosive sublimate ; and that the specimens are best
finished by varnishing, after one or two coats of size, with common
oak-varnish.
xxii INTRODUCTION.
During the dissection of any animal it is always advisable
to have the skeleton at hand for reference, and at some time
or other a systematic study should be made of it. It is for
this reason that an account of the skeleton is prefixed to the
directions for the dissection of each type.
With slight variations the management of the work is the
same for all the subjects selected. The external characters
are first studied: then a rough dissection is made for the
purpose of acquainting the student with the position and
general relations of the chief organs ; at the conclusion of
this stage the brain is removed and preserved for future
examination ; finally, the various parts are studied more or
less in detail. ‘The student should try and arrange his work
so as to get the brain removed on the first day.
In the case of the Lamprey and the Lizard, which can be
satisfactorily preserved whole in alcohol, it has not been
thought necessary to remove the brain until it is wanted for
dissection.
The directions for each stage in the dissection are given
in “indented ” paragraphs numbered with Roman numerals ;
the following ordinary paragraphs with Arabic numerals
giving descriptions of the structures brought into view by
such dissection. By this arrangement the work is divided
into sections, many of which may be omitted without serious
disadvantage, if time runs short. The paragraphs in small
type may also be omitted by the beginner.
When a dissection is prolonged over say two days, the
subject should be placed, when not in use, in a preservative
INTRODUCTION. xxiii
fluid, such as methylated spirit, Wickersheimer’s fluid,’ or
boro-glycerine.
I should strongly advise students to adopt the plan so
much insisted upon by Professors Huxley and Martin in
their Evementary Biology, of making sketches of their
dissections. Even a rough drawing, if the various parts
are properly named, and especially if they are further
distinguished by different colours, forms a far better
memorandum of work done than any mere description.
1 This fluid is made as follows: dissolve 100 grams of alum, 25 of
common salt, 12 of saltpetre, 60 of potassic carbonate, and 20 of
arsenious acid in 3 litres of boiling water, and add 1°2 litre of glycerine
and 0°3 litre of methylated alcohol.
ZOOTOMY.
THE LAMPREY.
THE Sea Lamprey (Péetromyzon marinus).
THE FRESH-WATER LaMPREY, OR LaMPERN (P. fluviatilis).
A.—THE SKELETON.
I. The preparation of the lamprey’s skeleton is a very
laborious process, owing to the extreme toughness
of the connective tissue which invests it. Re-
moval of the latter is assisted by maceration in
nitric acid, 10 per cent., care being taken not to
allow the acid to act too long, the result of pro-
longed maceration being the entire separation of
the cartilages of the skull proper, and the total
destruction of the branchial basket. In preparing
a skeleton fot demonstration purposes, it is, how-
ever, advantageous to allow the cartilages to se-
parate, and then to articulate them with fine
platinum wire. The branchial basket can then
be shown by itself in a special dissection. The
€ B
2 ZOOTOMY.
skeleton may be either kept in spirit or prepared
as follows :—
(a) Place for about three days in a solution
composed of
Glycerine . ro parts.
Water LO <5
Corrosive sublimate . ; OE 45
Alum ‘ OFZ 45
(2) Transfer to melted glycerine jelly made by
dissolving 2 parts of gelatine, or “ gelatine glue,”
in the above fluid : allow to remain for 2 to 4 days
at a temperature just sufficient to keep the jelly
fluid.
(c) Place in a dry room, until the surface no
longer feels damp or sticky ; then varnish with a
solution of white (bleached) shellac in rectified
spirit.
Il. In the prepared skeleton make out the following
points :-—
1. The notochord (Fig. 1, 7c), a cylindrical rod, occupy-
ing the position of the vertebral column in one of the
higher animals ; at its anterior end it tapers to a point some-
what suddenly ; at its posterior end the tapering is more
gradual. It is composed of a strong sheath of cartilage,
inclosing a gelatinous central substance (Figs. 4, 6, 7, 8, 70).
2. The neural processes (Fig. 1 and 6 ~.p), smal! rods
of cartilage, set in pairs at short intervals alongthe dorso-lateral
regions of the notochord, and partly inclosing the neural
canal (Figs. 4 and 6—8, z.ca), in which the spinal cord
lies. Between the neural processes and completing the
shutting-in of the neural canal both dorsally and laterally is
a quantity of very tough pigmented fibrous tissue (Figs. 4,
and 6—8, 4).
‘sainpiade yertpueiq [eusayxa ‘L—z : uauivroy pearmadiy ‘A : uaureioy odo “TJ + asvo ureaq Jo [[eM apts ‘ar
ryoyseq [eIqouwlq jo adepyqwo fesuaa “7-2 ; yore aepnooqns jo ssesoid muuytAls “Pye : aBepyswo wopyAys ys
: yore qe[nvoqns jo ssavoid Jerayey rotsaysod ‘¢y"¢ : a8evyyswo Yerajye] Aoweysod ‘7-d : aBvpAVO pesiop A01Ia}sod
‘og : asenaes petpreotwad ‘9g : yore yeyidioo0 ‘vo : sassaooid yeimau ‘g'z% : psoypojou ‘9% : apnsdeo yeseu ‘yee
1 OBELIVS [VIJUSA UeIpauT ‘aw : sadwyavo penSury Arossaooe 4,57 (57 : aBvpyysvo yenSury ‘37 : Joyseq yerouesq jo
adel Awd Jesiop ‘7p : adv[IIeo enus0d ‘9-9 : oSvpyjzeo [epsoyoured 10 peseq yo uosod peyuaa ‘¢'g pue ‘{usiop ‘¢'g
? amnsdvo Aroypne ‘vp : aSernzeo aejnuue ‘wn : yore rvndoqns jo ssado1d yesoye] AOVAIUE “¢'7-y +: aBepyIVO [eIDIe]
Jolajue 7'p : edvpyIVS [sop roL1ayUe ‘p'y : YI § UoIdrIOsep 995 { Jayseq [eu dy} Jo sucKIod snorrea ‘y—v
*(azIs *yeu) proysojou ayy
Jo yxed soj19jue pue jayseq yerpouIg ay} YM aps Yar oq} Wo [[MYs oy], “snuwew uozhwoyeg—! ‘oy
i
as im,
4 ZOOTOMY.
3. The fin-rays (Figs. 7 and 8, /7), delicate cartilaginous
filaments, supporting the dorsal and caudal fins ($§ 29, 30).
They are connected ventrally with the fibrous tissue cover-
ing in the neural canal, and lie parallel to one another and
inclined backwards.
4. The brain-case, or hindmost division of the skull.
Posteriorly it consists of a basal or parachordal plate
(Figs. 1 and 2, 3.f, 8.9’), surrounding the anterior end of
the notochord, and divided by the latter into dorsal (.A)
and ventral (4.f’) portions. The ventral portion forms a
continuous plate beneath the anterior end of the notochord
(Figs. 2 and 4, 4’); the dorsal portion consists of two
Fic, 2,—Petromyzon marinus. The brain case, from above, the
subocular arches supposed to be removed (nat. size: from a larger
specimen than Fig. 1).
au, auditory capsules: 4.2, dorsal, and 4.7’, ventral portion of
basal or parachordal plate: 4.4, hard palate: a.p, naso-palatine
canal: oc, occipital arch: ¢7, trabecula : w, side wall: II, optic fora-
men. V, trigeminal foramen.
longitudinal plates, which do not unite over the notochord.
Anteriorly the basal plate is continued forward into two
flattened plates, the trabecule (Fig. 2, 7), which unite
with one another in front, forming the hard palate (4.9),
and inclosing an oval space, the naso-palatine canal
(na.p). laterally, the trabecule and hard palate send up
plates of cartilage (z), which afford side walls to the brain-
THE LAMPREY. 5
case, and unite with one another above the brain in a narrow
band, the so-called occipital arch (0.c). The side walls
are perforated with apertures for the exit of the optic (II),
and of the fifth and seventh (V) nerves.
5. The auditory capsules (Figs. 1 and 2, au), paired
ovoidal masses of cartilage, fused with the basal plate and
cranial walls, and each containing a cavity for the correspond-
ing auditory sac (§ 95); their inner walls bound laterally
the posterior part of the brain cavity, and are pierced with
apertures for the auditory nerves.
6. The nasal capsule (Fig. 1, za; Fig. 3), a concavo-
convex plate of cartilage, of irregularly oval form, lying with
its concave side forwards, in the posterior wall of the nasal
sac (§ 89), and forming the anterior boundary of the cerebral
Fic. 3.—Petromyzon marinus. The nasal capsule, front view (nat.
size). I, olfactory foramina.
cavity (see Fig. 4 za.c). Near its centre it is perforated by
two oval apertures (Fig. 3, 1) for the passage of the
olfactory nerves.
7. The subocular arches, each consisting of an
anterior lateral process (Fig. 1, a./), springing from
the anterior end of the hard palate, and of a posterior
lateral process (2.44), arising from the basal plate just
beneath the auditory capsule. Both processes pass down-
wards, outwards, and forwards, and meet with one another
at an acute angle.
8. The styliform processes (Fig. 1, s¢.), cylindrical
rods springing one from the posterior edge of each posterior
lateral process, near its proximal end, and taking a directly
downward course.
6 ZOOTOMY.
9. The cornual cartilages (Fig. 1, ¢c), small, irregular,
horizontal pieces, connected by fibrous tissue to the distal
ends of the styliform processes.
10. The posterior dorsal cartilage (Figs. 1 and 4,
p.@), an arched plate, bilobed anteriorly, and truncated
posteriorly, where it enters into fibrous union with the
anterior edge of the hard palate.
11. The anterior dorsal cartilage (Figs. 1 and 4,
a.@ ), situated in front of and partly overlapped by the fore-
going ; it is strongly arched from side to side, ends in front
in a thin rounded edge, and posteriorly is produced on each
side into a downwardly directed process.
12. The anterior lateral cartilages (Fig. 1, a./),
situated one on either side, just in front of the descending
process of the anterior dorsal cartilage ; their form is some-
what sigmoidal.
13. The posterior lateral cartilages (Fig. 1, 2./),
flattened plates, situated one on either side beneath the pos-
terior dorsal cartilage, and between the descending process
of the anterior dorsal cartilage, and the anterior lateral
process of the subocular arch.
14. The lingual cartilage (Figs. 1 and 4, 4), a long
median ventral piece, flattened from side to side, truncated
in front, and tapering posteriorly ; by its anterior end it is
united by fibrous tissue to a small cartilage (/e’) having the
form of a semicircle, and set transversely: with the free,
upwardly directed ends of this are connected two small
irregular cartilages (/g"). The lingual cartilage lies in the
floor of the mouth; the semicircular cartilage (/e’) sup-
ports the median portion of the tongue ; the small cartilages
(Zg") lie in the lateral wings of the tongue (§ 23,
Fig. 4, 42’).
15. The median ventral cartilage (Figs. 1 and 4,
THE LAMPREY. 7
m.v), a slender rod, having the form of a T with a very
long stem, and situated in the middle line beneath the
lingual cartilage, the anterior ends of the two being con-
nected by fibrous tissue.
16. The annular cartilage (Figs. 1 and 4, az), a stout
circular cartilage, supporting the oral funnel (§ 21), and
giving attachment to the maxillary and mandibular teeth
(§ 24).
17. The styliform cartilages (Fig. 1, s¢), two
elongated, tapering rods, attached by their thickened proxi-
mal ends to the posterior edge of the annular cartilage, a
little below its middle, and directed backwards and some-
what downwards.
18. The branchial basket (Fig. 1, dc, v.c, a—h, pc),
a cartilaginous framework supporting the gills. It consists
essentially, on each side, of (1) a longitudinal rod or dorsal
cartilage (d¢.c), springing from the dorsal portion of the para-
chordal (2.f), and passing backwards along the side of the
notochord; (2) a second longitudinal rod or ventral
cartilage (v.c), lying, close alongside, and partly fused with,
its fellow of the opposite side, in the middle ventral line ;
(3) irregular transverse arches (a—g, &) uniting the dorsal
and ventral cartilages and passing between the outer gill-
clefts; (4) lateral longitudinal bars (4%, 7) connecting the
transverse arches immediately above and immediately below
the gill-clefts; and (5) a cartilage (gc) supporting the
posterior and lateral walls of the pericardium.
Each of the transverse arches, except the first and the eighth or
last, consists of seven well-marked portions; of these, the first or
dorsalmost (a) and the seventh or ventralmost (g) are flattened plates,
produced into longer or shorter anterior and posterior processes; the
second (4) and sixth (/) are short curved rods; the third (c) and fifth
(e) are flattened, and are produced into forwardly directed processes ;
the fourth or middle portion (d) is a curved rod situated immediately
8 ZOOTOMY.
behind the corresponding gill-cleft. The longitudinal connecting bars
(2 and 2) are flattened, and unite with the third (c) and the fifth (e)
segments of the transverse arches respectively. In front of the first gill-
cleft the two longitudinal connecting bars run together and form a
single rod, which becomes connected with the first transverse arch (é).
This latter is free at its dorsal end, of tolerably regular cylindrical form,
and united by a short rod of cartilage with the proximal end of the
styliform process (s¢.9). The eighth transverse arch is also regularly
cylindrical at its dorsal and ventral ends, but in the middle of its
course becomes fused with the hinder ends of the longitudinal connect-
ing bars and with the pericardial cartilage (fc). The latter has the
form of a backwardly directed hemisphesical cup, supporting the
posterior wall of the pericardium, and produced into dorsal, ventral,
and lateral processes, of which the last enter into union with the bran-
chial basket proper, as already described.
The cartilages of the branchial basket lie, for the most part, immedi-
ately beneath the dorsal and ventral muscles covering the gills (§ 34, Fig.
6, 2, 2), so that they are seen at once when those muscles are removed :
but the pieces marked 4, d, and f, are curved inwards and are con-
sequently not seen until the surrounding tissues are dissected away.1
B.—Directions for Dissection.
III. Verify the following external characters :—
19. The elongated vermiform body, almost circular in
section anteriorly, but becoming compressed from side to
side posteriorly ; the head passes insensibly into the trunk,
and the trunk into the tail.
20. The integument, smooth and slimy, and entirely
devoid of scales: marbled with black in P. marinus, of a
uniform bronze-green tint in P. fluviatilis.
24. The sucker-like oral funnel (Fig. 4, o,f) at the
anterior end of the body, inclined obliquely downwards and
forwards: its rim, which is beset with numerous vascular
papilla, passes insensibly into the general surface of the
?This description of the branchial basket is taken from a single
specimen of P, marinus—the only one at my disposal.
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TO ZOOTOMY.
body above and at the sides, while below it is separated by
a deep furrow (Fig. 4, g7).
22. The mouth (Fig. 4, m), situated at the bottom of
the oral funnel, and of a somewhat crescentic form.
23. The tongue (Fig. 4, 7), the end of which forms a
well-marked protuberance bounding the mouth below, and
produced on either side into an upwardly directed, wing-like
process (¢).
24. The yellow horny teeth, which beset the inner
surface of the oral funnel and the tip of the tongue: one
immediately above the opening of the mouth is large and
bifid, and is distinguished as the maxillary tooth; those
on the tongue are the lingual teeth; and a transverse
crescentic ridge, below the tongue, and produced into
several cusps, is known as the mandibular tooth.
In P, marinus the two cusps of the maxillary tooth are close together,
and the lingual teeth consist of two pairs of lunate denticulate ridges,
the two ventral united with one another in the middle line. In P.
fluviatilis the cusps of the maxillary tooth are somewhat widely sepa-
rated, the dorsal lingual teeth are absent, and the ventral are united to
form a strong transverse ridge, with a prominent median cusp.
25. The nostril, a single median aperture on the upper
surface of the head, a short distance from its anterior end.
26. The eyes, situated at the sides of the head, a little
posterior to the nostril; they are devoid of eyelids, but
covered with transparent integument.
27. The external branchial apertures (Figs. 4 and 6,
é.@), a row of seven small slits on each side of the head,
the first a little behind the eye.
28. The urinogenital papilla (Fig. 5, ~g.f), a small
elevation, situated in the median ventral line, at about a
quarter of the length of the body from the hinder end. It
is pierced at its summit by a small opening—the urino-
THE LAMPREY. II
genital aperture (z),—and lies in an oval depression, in
the anterior part of which, just in front of the base of the
papilla, is another small aperture, the anus (a).
29. The two dorsal fins (Figs. 7 and 8), median longi-
tudinal folds of the integument: the anterior end of the
first is near the middle of the body, that of the second
somewhat in front of a vertical line taken through the anus.
30. The caudal fin, continuous in front with the second
dorsal, and continued round the end of the tail on to its
ventral edge; it is diphycercal, that is, evenly distributed
above and below the axis of the tail.
Fic. 5.—Petromyzon marinus, The urinogenital sinus, with the
rectum and part of the left kidney (nat. size).
@, anus: zvf, intestine: 2, left kidney: 7, rectum: w.9.f, urino-
genital papilla: w.g.s, urinogenital sinus: wz, left ureter, «, aper-
ture of left, and x’ aperture of right ureter into urinogenital sinus :
y, bristle passed through right abdominal pore: z, bristle passed into
urinogenital sinus through its external aperture.
31. The absence of paired fins, or fore and hind limbs.
32. The apertures of the sensory tubes, minute
punctiform openings on the surface of the head.
IV. Remove the skin from the anterior part of one
side of the body, from the end of the mouth toa
short distance behind the gill-slits, and from the
middle dorsal to the middle ventral line: make
out—
33. The body muscles, lying beneath the skin, and
12 ZOOTOMY.
arranged in transverse segments, called myotomes or
myocommas, separated from one another by strong plates
of fibrous tissue.
Each myotome takes a zigzag course ; starting from the middle dorsal
line, it passes first sharply backwards, then more gently forwards, then
backwards, and finally sharply forwards. The plane of the myotomes
is not at right angles to the long axis of the body, but is inclined from
the surface, inwards and forwards, The muscular fibres of which they
are composed are longitudinal, 7.e, at right angles to the general direction
of the myotomes themselves.
Fic. 6.—Petromyzon marinus. Transverse section through the
branchial region, semi-diagrammatic (nat. size). The gill sacs are
supposed to be rotated forwards, so as to bring the external in the
same plane as the internal branchial apertures.
ér.m., branchial membrane: d.ao, dorsal aorta: d.c, dorsal carti-
lage of branchial basket: d.m, dorsal body-muscles: ¢.a, external
branchial aperture: f¢, fibrous tissue inclosing neural canal: 4, 2,
lateral longitudinal cartilages of branchial basket : z.@, internal branchial
aperture : z.7z, inferior jugular vein: /v, jugular vein : my, myelon :
nc, notochord : z.ca, neural canal: 2.2, neural processes : @s, ceso-
phagus : g.6r, peri-branchial sinus : 7.7.4, retractor muscle of tongue :
r.t, respiratory tube : s, circum-cesophageal sinus : v.ao, ventral aorta ;
v.c, ventral cartilage of branchial basket : v.#, ventral body-muscle.
34. The division of the myotomes, immediately behind
the last gill-cleft, into two longitudinal masses, a dorsal and
THE LAMPREY. 13
a ventral, which pass forwards, the one above, the other
below the line of branchial apertures, leaving these latter
uncovered.
The dorsal muscle is inserted partly by a broad tendon to the posterior
dorsal cartilage (§ 10), and partly into the fibrous posterior wall of the
orbit ; the ventral muscle is inserted by a longish tendon into the annular
cartilage (§ 16).
35. The great mass of radiating muscular fibre, which,
now the skin is removed, forms the outer surface of the oral
funnel.
V. Make a median ventral incision through the skin
and muscle forming the walls of the body, begin-
ning about the middle of the body, and proceeding
forwards to within about half an inch of the last
gill-cleft, and backwards to within about an eighth
of an inch of the anus. From the ends of this
incision carry up vertical incisions on the left side
and remove the long flap thus made, so as to
expose the body-cavity from the left side.
Great care must be taken not to injure the liver
(§ 37), the left kidney (§ 40), or the rectum (§ 39).
The following points can now be made out :—
36. The pigmented peritoneum lining the whole body-
cavity.
37. The liver (Fig. 4, Zr), at the anterior end of the
cavity, deep red in the fresh condition in P. fluviatilis,
greenish in P. marinus. It consists of a single lobe,
convex on the ventral side, excavated cae for the
genital gland (§ 38) and intestine (§ 39), hollowed out
anteriorly for the pericardium (§ 44), which it partly covers,
and ending in a blunt point posteriorly.
38. The single genital gland (testis or ovary), oc-
cupying in the adult the greater part of the body cavity :
14 ZOOTOMY.
the testis is a soft, greatly lobulated organ, closely resembling
fat: the ovary (Fig. 4, 07), is also multilobular, each lobe
containing numerous eggs, each about the size of a pin’s head.
The genital gland is suspended to the dorsal wall of the
abdomen by a sheet of peritoneum, called mesorchium in
the case of the male, mesoarium in that of the female.
In the breeding season, the body cavity is found to be quite
full of liberated ova, and the ovary itself is much reduced.
Fic. 7.—Petromyzon marinus. Transverse section through the
abdominal region, including the first dorsal fin (nat. size).
cd, cardinal veins: d.ao, dorsal aorta : Jv, fin rays: f.4, fibrous
tissue inclosing neural canal : 7#, intestine, the line pointing to the
spiral valve: 4, kidneys: /y, sub-vertebral lymph sinus : m, body-
muscles : zy, myelon : 2c, notochord : n.ca, neural canal: Zs, testis :
ur, ureter,
39. The intestine (Figs. 4 and 7, i#), a straight, very
slender tube, entering the body-cavity at its anterior end
and on the dorsal side: it passes backwards between the
liver and the genital gland, and then between the lobes of
the ‘latter, till it reaches the posterior end of the body-cavity,
where it dilates into the rectum (Fig. 5, r), and ends by
THE LAMPREY. 15
the anus (a). The intestine is quite free for the greater
part of its length, but at its hinder- end is attached to the
dorsal wall of the body-cavity by several delicate mesen-
teric bands, carrying blood-vessels, while in front it is
firmly connected by fibre with the anterior half of the dorsal
surface of the liver.
40. The kidneys (Figs. 5 and 7, 4), two elongated
band-like organs, of a deep red colour, attached by peri-
toneum one on each side to the dorsal wall of the body-
cavity, and extending from about the middle of the latter to
within a short distance of the anus.
41. The ureters (Figs. 5 and 7, m7), delicate tubes as
wide as, or wider than the intestine, and attached all along
the free (outer or ventral) edge of the kidneys: passing
backwards they become connected with
42. The urinogenital sinus (Fig. 5, ~g.s), a small
ovoidal sac, lying close behind the rectum, and becoming
narrowed ventrally to form the urinogenital papilla
(w.¢.).
43. The sub-vertebral lymph sinus (Fig. 7, Zy), a considerable
cavity included between the layers of peritoneum supporting the kidneys
and genital gland : it is divided into two by a median vertical partition.
44. Note also the pericardium (Fig. 4, Zc), lying just
in front of and partly covered by the liver: its almost
hemispherical posterior wall, strengthened by cartilage
($ 18, Fig. 1, fc) is all that can be seen at present.
VI. Open the urinogenital sinus by carefully slitting up its left
wall, first introducing a guarded bristle! by the external
aperture : observe—
45. The apertures of the ureters (Fig. 5, x, 2’), situated close
together in the antero-dorsal region of the sinus.
1 That is, a bristle tipped with a small knob of sealing-wax.
16 ZOOTOMY.
46. The abdominal pores (Fig. 5, y), small apertures situated one
in each lateral wall of the sinus (the left will probably have been
destroyed in opening the latter), and establishing a communication
between the sinus and the body-cavity, through which the generative
products escape.
VII. Open the intestine by a longitudinal incision along its whole
length : note—
47. The spiral valve (Figs. 4 and 7, zz¢), a longitudinal fold of
mucous membrane, projecting into the cavity of the intestine, and
having a slight spiral twist.
48. The aperture of the cesophagus (Fig. 4, y), a longitudinal
valve or slit, a short distance from the anterior end of the gut, and on
its right side: in front of this aperture, the intestine is produced for-
wards into a short thick-walled, blind pouch, situated to the left of the
posterior end of the gullet and of the sinus venosus (§ 71). This will
probably be seen better at a later stage (§ 59).
49. In P, marinus, the aperture of the bile duct (Fig. 4, 4.¢), on the
ventral wall of the gut, just at the point where the latter becomes free
from its attachment to the liver. The bile duct is absent in the adult
P. fluviatilis, and is not usually present in P. marinus, though very dis-
tinct in the specimen figured. The spiral valve begins just posterior to
this point.
VIII. Turn the animal to the supine position (ventral
aspect uppermost), and see the relations of the
chief organs from the new point of view. Then
remove the ovary or testis, the kidneys, and all
but the anterior inch or so of the intestine: make
out now—
50. The cardinal veins (Figs. 4, 6, and 7, ca), two large
vessels, lying one on each side of the middle line in the
dorsal wall of the body-cavity.
51. The dorsal aorta (Figs. 4, 6, and 7, dao), a small
vessel, lying in the middle line between the two cardinal
veins.
52. Traced backwards, the cardinal veins are found at the posterior
end of the body-cavity to unite into a single trunk, or rather to
THE LAMPREY, 7
be formed by the bifurcation of a single trunk, the caudal vein (Fig.
8, ¢.v), which may be traced to the end of the tail, lying to the ventral
side of the caudal artery (Fig, 8, c.2), which is the direct continua-
tion of the dorsal aorta.
Fic. 8.—Petromyzon marinus, Transverse section through caudal
region, including the second dorsal fin (nat. size).
c.a, caudal artery : ¢.v, caudal vein: fir, fin rays: fit, £7’, fibrous
tissue enclosing neural canal: m, bedy-muscles: my, myelon: xc,
notochord : #.ca, neural canal.
IX. Place the fish once more with the left side up-
wards ; dissect away the dorsal and ventral muscles
of the branchial region (§ 34), and, if the skeleton
has not been examined, make out the various
cartilages of the branchial basket (§ 18): then
remove the latter, as well as the muscular and
connective tissues obscuring the gill-sacs (§ 53):
get the latter well cleaned, open one or two of
them and note :—
53. The gill-sacs (Figs. 4 47, and 6), seven in number,
arranged obliquely, each being inclined, from its inner side,
backwards and outwards. They are compressed from
before backwards, separated from one another by strong
fibrous and muscular partitions, and marked externally with
parallel horizontal lines, which mark the position of—
€
18 ZOOTOMY.
54. The branchial filaments, sub-parallel ridges of
the mucous membrane, lining the gill-sacs, and encroaching
largely upon the cavity of the sacs.
The whole set of filamen's on each side of each sac constitutes a
demibranch or half-gill : the septum between any two sacs, together
with the two contiguous demibranchs, answers to a single gill of one
of the higher fishes, (See p. 46, § 84, and p. 103, § 89.)
55. The internal branchial apertures (Figs. 4 and
6, 2c), on the inner walls of the gill-sacs, leading into the
respiratory tube presently to be seen (§ 58).
56. The peribranchial sinuses (Fig. 6, #.67), considerable
spaces included between the gill-sacs themselves and the partitions
which separate them.
X. Remove the gill-sacs, cutting them away close round
the internal branchial apertures, but taking great
care not to injure the respiratory tube (§ 58),
gullet (§ 59), &c.: also dissect away enough of
the dorsal body muscles to allow of the structures
mentioned being brought clearly into view. Ob-
serve the following :—
57. The retractor muscles of the tongue (Fig. 4,
r.m.t), surrounding the lingual cartilage (§ 14, Figs. 1
and 4, 7), and forming a prominent cylindrical fleshy mass,
in the middle ventral line, separating the gill-sacs of opposite
sides, and extending back as far as the pericardium.
58. The delicate membranous respiratory tube (Figs.
4 and 6, 7.#), lying almost immediately above the retractor
of the tongue ': the seven internal branchial apertures of
the left side are seen perforating its lateral wall.
59. The cesophagus (Figs. 4 and 6, es), lying imme-
diately above the respiratory tube, and becoming continuous
1 The ventral aorta which is between the two will be mentioned
subsequently (§ 72).
THE LAMPREY. 19
posteriorly with the intestine in the antero-dorsal region of
the body-cavity. Its diameter is not more than half that of
the respiratory tube, and its walls are very delicate and
easily torn. The best way to make it out without damage
is to pass a guarded bristle into it from the already opened
intestine.
60. The pericardium, a large chamber, lying immedi-
ately behind the last pair of gill-sacs: its posterior wall, as
already seen (§ 44), 1s strongly convex ; its anterior surface
fits closely against the hinder or inner walls of the last pair
of branchial sacs, and presents therefore a double concavity.
In the present view, of course, only the left of these con-
cavities is seen.
61, The circum-cesophageal sinus (Figs. 4 and 6, s), a consider-
able longitudinal cavity, lying above and at the sides of the gullet, and
imperfectly divided into two tubes by a perforated vertical partition which
is related to the gullet likea mesentery. Behind the posterior end of the
respiratory tube, the sinus extends also below the gullet as far downwards
as the ventral aorta (§ 72) and between the inner or posterior walls of the
last pair of gill-sacs, this portion (Fig. 4, s’) being also divided by a per-
forated vertical partition, The cavity is related to the gullet in much
the same way as the Lody-cavity to the intestine.
XI. If the anterior (pre-branchial) portion of the ven-
tral body-muscle (§ 34) is still left, remove it, and
note
62. A great mass of muscle, forming a prominent pro-
jection beneath the eye, and just in front of the gills : it
forms the lateral boundary of the mouth-cavity and contains
imbedded in it the subocular arch (§ 7), styliform process
(§ 8), and cornual cartilage (§ 9).
63. The salivary sac, appearing as a dark patch on the ventro-
lateral region of the above mass of muscle ; when cut into, it is seen to
be a cavity with glandular walls: it is said to open by a fine duct
into the mouth.
C 2
20 ZOOTOMY.
XII. Remove the eye, and dissect away the muscles,
cartilages, &c. (§ 62), which form the left side
wall of the mouth-cavity, first passing a probe
into the latter from the oral aperture to guard
against cutting too deeply. Also open the cesopha-
gus and the respiratory tube by a longitudinal
incision along the left side of each. The following
points can now be made out :—
64. The almost tubular oral cavity (Fig. 4, 7), com-
municating with the oral funnel by the very narrow oral
aperture.
65. The oral czecum, a blind pouch of the mucous membrane in
about the middle of the mouth-cavity, on the dorsal side (Fig 4, ™) ;
it is continued posteriorly into a longitudinal groove.
66. The aperture of the cesophagus (Fig. 4, between
m and @s), at the hinder end of the oral cavity, and im-
mediately beneath it, that of the respiratory tube.
Between the two apertures the mucous membrane forms a
sort of horizontal shelf, produced into five finger-like pro-
cesses in P. fluviatilis, and in P. marinus into two
blunt processes supported by small cartilages. The entrance
of the respiratory tube is also guarded by two lateral flaps of
mucous membrane, the vela. (Fig. 4, v/).
67. The spirally arranged ridges into which the mucous membrane
of the gullet is produced.
68. The extent of the respiratory tube, and the internal
branchial apertures of the right side.
XIJIL Open the pericardium by carefully removing the
greater part of its left wall : note
69. The auricle (Fig. 4, aw), occupying the whole of the
left side of the pericardial chamber, and therefore the only
part of the heart seen at first. It is strongly convex on its
THE LAMPREY. 21
dorsal and left side where it comes in contact with the peri-
cardium, while on the right it adapts itself to the form of
the ventricle.
7°. The ventricle (Fig. 4, v), seen. by lifting up the
auricle to lie towards the right side of the pericardium: it
has a prismoidal form, and is of firmer texture than the
auricle.
71. The sinus venosus (Fig. 4, s.v), a tubular
chamber, passing almost vertically from the dorsal to the
ventral wall of the pericardium, between the auricle and
ventricle : it is attached to the posterior wall of the pericar-
dium by a thin vertical sheet of connective tissue.
72. The ventral aorta (Fig. 4. v.a0), springing from the
anterior end of the ventricle, and passing through the wall
of the pericardium, forwards and in the middle line,
between the respiratory tube above and the retractor of the
tongue below.
Opposite the fourth gill-sac’the ventral aorta bifurcates and is con-
tinued forwards as two parallel trunks. From each of these are given
off four afferent branchial arteries, the first supplying the first demi-
branch (anterior wall of first gill-sac), the second, the second and third
demibranchs (posterior wall of first and anterior wall of second sac),
the third, the fourth and fifth demibranch, and so on. The azygous
posterior portion of the ventral aorta also gives off four afferent arteries,
of which the first three supply each two contiguous demibranchs (2.z.
one entire gill), and the fourth goes to the fourteenth or last demibranch,
Each afferent artery is thus primarily related to a gill (§ 54) and not
to a gill-sac.
73. The inferior jugular vein (Fig. 4, 7.7u) situated just below
the retractor of the tongue and above the median ventral cartilage of
the branchial basket. It brings the blood from the lower part of the
head to the sinus venosus, and is best made out by making a small
aperture in the latter and passing a probe forwards.
74. The dorsal aorta (Figs. 4 & 6, d.ao), immediately
22 ZOOTOMY.
beneath the notochord; it receives the efferent branchial
arteries from the gills.
XIV. Remove the outer (left) wall of the auricle, and
observe
75. The comparatively thin walls of the auricle,
strengthened by a network of pectinate muscles.
76. The auriculo-ventricular valve (Fig. 4, see
description), composed of two membranous flaps, and
guarding the oval opening leading from the auricle to the
ventricle.
77. The sinu-auricular valve (Fig. 4, x), also com-
posed of two flaps, and guarding the large aperture which
leads from the sinus venosus into the auricle.
XV. Pass a guarded bristle through the sinu-auricular
valve upwards along the sinus venosus as far as it
will go: also make an aperture in the left cardinal
vein, pass a probe forwards, and open the vein
along it.
78. It will be found that the cavities of the two cardinals
unite with one another by an oval aperture (Fig. 4, x) just
above the dorsal end of the sinus venosus, and that, at the
same place, they both communicate with the sinus.
79. The blood from the anterior part of the body, except that re-
turned by the inferior jugular, is brought back by the jugular veins
(Figs. 4 and 6, 7w), which lie one on either side of the notochord,
and, uniting each with the corresponding cardinal, pour their blood
into the sinus venosus. The jugular is best made out by passing a
guarded bristle forwards from the cardinal and gradually dissecting
down to it.
80. The hepatic vein (Fig. 4, 4.v) may also be seen at this
stage; leaving the liver, it pierces the pericardium and enters the
sinus venosus at the sane point as the inferior jugular.
XVI. Open the ventricle and note
81. The thick fleshy walls and small cavity.
THE LAMPREY. 23
82, The two membranous semilunar aortic valves
between the ventricle and the ventral aorta.
XVII. Turn the fish with the dorsal side upwards; dis-
sect away the muscles on the top of the head for
about an inch (P. fluviatilis) or two inches (P.
marinus) behind the nasal aperture; proceed
until the brain, the nasal sac (§ 89), and the audi-
tory capsules (§ 5) are exposed ; remove the roof
from the latter. Observe the following :—
83. The flat band-like spinal cord or myelon (Figs. 4,
6—8, my, and 9), lying loosely in the neural canal (x.ca),
and passing in front into the brain (Figs. 4 47, and 9),
which nearly fills the small cranial cavity.
84. The medulla oblongata or myelencephalon
(Fig. 9, 2.0), the hindmost division of the brain, passing
insensibly into the spinal cord behind, and on its upper
surface presenting an escutcheon-shaped cavity, covered
only by pia mater, the fourth ventricle or myeloccele
(v. 4).
85. The thin ledge of nervous matter overhanging the
anterior end of the fourth ventricle is all that represents the
cerebellum or epencephalon (Fig. 9, ).
86. The mid-brain, or mesencephalon (Fig. 9, o./).
consisting on the upper surface of a pair of rounded eleva-
tions, the optic lobes, immediately anterior to the me-
dulla ; they contain a cavity, the aqueduct of Sylvius,
or mesoccele (ag.s), open above, save for pia mater, and
in communication behind with the fourth ventricle.
87. The thalamencephalon, or twixt-brain (Fig. 9,
th), situated just in front of the mesencephalon ; it consists
of two paired masses, the thalami optici, between which
is a cavity, the third ventricle, or thalamoccele (z.3),
continuous behind with the aqueduct of Sylvius.
24 ZOOTOMY.
88. Two paired, somewhat kidney-shaped masses, forming
the anterior division of the brain, and having their convexi-
ties towards the middle line ; they are divided by depressions
on their outer sides into two parts, the smaller posterior
part answering to cerebral hemispheres, or prosence-
phala (Fig. 9, ¢/), the larger anterior part to olfactory
lobes, or rhinencephala (o//).
89. The nasal sac (Fig. 4, za), a rounded chamber,
opening by a short tubular prolongation in the single nasal
aperture. On opening, it is seen to be lined with strongly
pigmented epithelium, and to have its walls much plaited.
Fic. 9.—Petromyzon marinus, The brain from the dorsal aspect,
with the right auditory sac (* 3).
ag.s, aqueduct of Sylvius : a.s.c, anterior semicircular canal: cd,
cerebellum : ¢.4, cerebral hemispheres: ».0, medulla oblongata: 0./,
optic lobes : off, olfactory lobes ; .5.c, posterior semicircular canal : ¢/,
thalamencephalon: v, vestibule: v.3, third ventricle: 7.4, fourth
ventricle : I—X, cerebral nerves,
go. The olfactory nerves (Fig. 9, I), passing directly forwards
from the rhinencephala to the nasal sac, through the apertures in the
nasal capsule (§ 6).
g1. The optic nerves (Fig. 9, II), springing from the ventral surface
of the thalamencephalon and passing directly outwards through the
optic foramina (§ 4) to the eyes.
92. The oculomotor (third) nerves (Fig. 9, IIT), springing from
THE LAMPREY. 25
the under side of the mesencephalon, and passing outwards and slightly
forwards to the orbit, where they supply most of the eye muscles.
93. The fourth pair of nerves (Fig. 9, IV), arising from the dorsal
side of the anterior end of the medulla. They supply the superior
oblique muscles of the eyes.
94. The large nerve cord formed by the united roots of the fifth and
seventh nerves (Fig. 9, V, VII), leaving the brain just in front of
the auditory capsule, and passing forwards and outwards.
95. The auditory sac (Fig. 9, 7), exposed by the
removal of the dorsal wall of the auditory capsule; it con-
sists of an ovoidal membranous sac, the vestibule (7),
presenting on its upper surface, towards the outer side, two
semicircular canals (a.s.c, .s.c), corresponding. to
the anterior and posterior canals of the higher vertebrata,
the horizontal canal being absent.
96. The auditory nerve (Fig. 9, VIII), passing directly outwards
from the medulla oblongata to the auditory sac.
97. The glossopharyngeal (ninth) and vagus (tenth) nerves (Fig.
9, IX, X), arising from the medulla oblongata, just posterior to the
auditory nerve, and passing backwards and outwards.
XVIII. With a guarded bristle find an aperture lying
in the anterior ventral region of the nasal sac, close
under the entrance of the external nasal canal (see
Fig. 4) ; pass the bristle carefully into the opening ;
it will be found to take a course backwards and
downwards. Without removing the bristle, turn the
fish once more with its left side upwards, and dissect
away the tissues between the anterior end of the
notochord and the roof of the mouth, until the
bristle is found. It will be found to have passed
into
98. The nasal czecum (Fig. 4, za’), a considerable
pouch, lying close under the anterior end of the notochord.
opening anteriorly, as already seen, into the ventral side of
26 ZOOTOMY.
the nasal sac, and behind ending blindly a little posterior te
the first internal gill-cleft. *
XIX. If another specimen is available, make a series
of transverse vertical sections through the entire
animal previously hardened in alcohol or chromic
acid (see Figs. 6—8). The sections should be
about 2 to 3mm. thick in P. fluviatilis, 8 to
ro mm. in P. marinus. Be careful not to dis-
turb the order of the sections. Examine each one
separately, both from its anterior and its posterior
face, and observe the precise relations of the various
structures already seen by dissection.’
1 Itis important not to omit this section unless time or material fails,
asit forms an excellent introduction to the art of interpreting sections,
THE SKATE.
THE SKATE (Layja batis).
THE THORNBACK (2. clavata).
THE Hometyn Ray (&. maculata).'
A.—THE SKELETON.
I. Tue skeleton of the skate is mainly cartilagi-
nous, being hardened only by a superficial de-
posit of calcific matter, and in the vertebral
column by internal laminz of the same material.
It is best prepared by immersing the fish, after
removal of the viscera, for a few seconds in hot
water a few degrees below the boiling-point. This
process softens the muscles and ligaments, and
allows of their being readily stripped off the
cartilage without injury to the latter. When pre-
pared in the cold, the toughness of the ligaments,
especially in the region of the vertebral column,
renders their removal a matter of great difficulty.
1 These are the three commonest species of the genus Raja brought
to the London market. For the distinguishing characters of the three
species see pp. 41 and 42, §§ 54and 60, Several of the figures are
taken from the common New Zealand species, 2. asuta.
28 ZOOTOMY.
As some parts of the skeleton are more delicate
than others, it is advisable, after a very short
immersion in hot water, to dissect off as much of
the flesh as will readily come away, and then to
remove the branchial arches (§§ 40 and 41) and to
disarticulate the skull and pectoral fins from their
attachments to the vertebral column. The latter
can then, if necessary, be subjected to a second
immersion in hot water. In cleaning the skeleton
special care is required to avoid injury to the
branchial arches (§ 41), the spiracular cartilage
(§ 37), and the labial cartilages (§ 34).
The skeleton must not be allowed to dry, but should
be either kept in spirit or prepared by the
glycerine jelly process described on p. 2, § 1. In
the latter case about three to five days’ immersion
in the glycerine fluid, and two to three days in
glycerine jelly, is required. During the process of
drying, it will be found advisable to fix out any
parts which show a tendency to twist or warp
with pieces of wood or strappings of paper or
calico.
II. In the skeleton as a whole, note
1. Its division into a, vertebral column, including dorsal
and caudal fins (§§ 3—16) ; 4, skull, composed of the brain-
case (§§ 17—33), and of a number of loosely-attached carti-
lages, consisting chiefly of the jaws and of the gill-arches
(§§ 34—41) ; ¢ shoulder-girdle and pectoral fins (§§ 42—49) ;
d, hip-girdle and pelvic fins (§§ 50—5 3).
2. The superficial crust of ossification on nearly all parts
of the skeleton, except some of the smaller cartilages,
which are entirely uncalcified, and the centra of the
vertebree, which are calcified in a special manner (§ 5): the
THE SKATE, 29
ossifications are deposited in the form of minute polygonal
plates, forming a mosaic over the whole surface.
III. In the vertebral column, make out
3..The anterior part of the column, consisting of a large
mass of cartilage—the anterior vertebral plate (Fig. 10,
a.v.p~),—not divided into distinct vertebre, except in its
posterior ventral portion, where there are rudimentary
centra. It presents an almost flat ventral surface, a strong
median dorsal ridge, and two lateral ridges, which, at about
the middle of the plate, are produced upwards, so as to be
nearly as high as the median ridge. The neural canal, for
the reception of the spinal cord, runs from end to end of the
plate, the side walls of which are perforated by two rows of
small apertures, for the passage of the dorsal and ventral
roots respectively of the spinal nerves. The antero-inferior
region of the vertebral plate is produced into a scoop-like
odontoid process, which fits between the condyles of the
skull (§ 19): on either side of this, on the front boundary
of the lateral ridge, is a smooth surface, with which one of
the condyles themselves articulates.
4. The remainder of the vertebral column, consisting of
distinct vertebrae, which are divided into two sets: the
trunk vertebree, extending from the posterior end of the
vertebral plate to the root of the tail, and the caudal
vertebrze, reaching to the end of that appendage.
IV. Examine the trunk vertebre ; some from the sur-
face ; some by means of longitudinal and trans-
verse sections; some by disarticulation from the
rest ; and others by allowing to dry. Make out
5. The centra of the vertebra (Figs. 11, 12, and 13, ¢),
cylindrical bodies with deeply-concave anterior and pos-
terior ends; these ends are formed by concavo-convex
plates of bone, which meet one another in the middle of the
30 ZOOTOMY,
Fic. 10.—Raja nasuta (female). The skeleton seen from the ventral
aspect (one-fourth nat. size). On the left side (right in the figure) the
pectoral and pelvic fins, and on the right the hyoid and branchial
arches (with the exception of the fifth cerato-branchial) and labial
cartilages are removed. Inthe remaining pectoral fin, only the proximal
ends of most cf the fin rays are shown, and the cartilaginous branchial
rays are omitted for clearness sake.
ac. I, a¢, 2, anterior and posterior acetabular facets : az¢, antorbital
cartilage : az, auditory capsule: a.v.g, anterior vertebral plate : c.d7. 3,
¢.ér, 5, third and fifth cerato-branchials: ¢f, coracoid fontanelle : «7,
THE SKATE. 31
coracoid : czy, ceratohyal :@br, 3, third epi-branchial : ey, epi-hyal :
gt. 1, gl. 2, gl. 3, anterior, middle, and posterior glenoid facets :
h.br, 1, h.br. 3, h.br. §, hypo-branchials of the first, third, and
fifth branchial arches: 4.4y, hypo-hyal: Am, hyomandibular: Aw
commencement of hzemal canal: 7/, iliac process: /b. 1, 6. 2, 2b. 3,
4. 4, labial cartilages : mck, Meckel’s cartilage or lower jaw: ms. pr,
mesopterygium: 2m.p/, metapterygium : o/, olfactory capsule : pp
propterygium: f.f%, pre-pubic process: ft.gz, pterygo-quadrate
cartilage, or upper jaw : fz, pubic portion of hip girdle : », rostrum :
r.c, rostral cartilage : sc, scapula: s.c.f, scapulo-coraccid fontanelle :
sf, spiracular cartilage: s.sc, supra-scapula.
longitudinal axis of the centrum; the cartilage intervening
between them is further strengthened by four radiating
plates of bone, which give rise to a cruciform figure in a
Fic. 11.—Raja nasuta. The last seven trunk vertebre, and the
first ten caudal vertebrze, viewed from the left side (nat. size).
¢, centra: cd. 1, first caudal vertebra : d.r, dorsal root of spinal
nerve: 4.f, hamal process : 4.5, heemal spine: 2.7, inter-neural plate :
n.p, neural process: #.5, meural spine: r, rib: 4, trunk of spinal
nerve: ¢r, transverse process: ¢. 28, twenty-eighth (last) trunk
vertebra: v.7, ventral root of spinal nerve.
transverse section of the centrum. The centra are seen to
continue backwards the ventral portion of the anterior
vertebral plate.
6. The transverse processes (Figs. 11 and 12, tr),
backwardly directed rods of cartilage, which proceed one
from either side of the centrum, and continue backwards
the lateral ridges of the vertebral plate.
32 ZOOTOMY.
7. The rudimentary ribs (Figs. 11 and 12, 7), small
pieces of cartilage attached to the ends of the transverse
processes.
Fic. 12,—Raja nasuta, A trunk vertebra, seen from the front
(nat. size),
¢, centrum : z., inter-neural plate: 7.2, neural process : #.s, neural
spine: 7, rib: 7”, transverse process.
8. The neural processes (Figs. 11, 12, and 13, 7.),
small triangular plates rising one from each side of the
dorsal surface of the centrum: a small aperture in each of
them transmits the ventral root of a spinal nerve (Fig.
II, U7).
g. The neural spines (Figs. 11, 12, and 13, #5), flat
plates dividing below into two triangular processes directed
outwards, so that the whole plate has, in transverse action,
the form of an inverted Y. Each neural spine is situated
immediately above the vertebra of which it forms a part,
but, save in exceptional cases, is not directly united with
the neural processes, so that the neural arch is, so far,
incomplete.
ro. The interneural (or intercrural) plates (Figs.
11, 12, and 13, z), six-sided plates of cartilage, which
complete the neural arches laterally, filling up at the same
time what would otherwise be the intervertebral foramina.
Each transmits the dorsal root of a spinal nerve (Fig. 11,
@.r), the ventral root of which traverses the neural process
next in front.
THE SKATE. 33
11. The intervertebral substance, a gelatinous tissue
filling up the biconvex spaces between contiguous vertebre,
and containing the remains of the embryonic notochord.
V. Examine the caudal vertebre in the same way:
make out the following points :—
12. The centrum of each vertebra (Figs. 11 and 14, ¢)
gives off, on each side, a downwardly-directed hemal
process (4.p), which is seen, by examining the transition
region between trunk and tail (Fig. 11), to be homologous
with the transverse process of a trunk vertebra: the hemal
processes, uniting below, form the heemal arch, which
Fic. 13.—Raja nasuta, Longitudinal vertical section of a trunk
vertebra (nat. size).
¢, centrum: 7.#., inter-neural plate: #.f, neural process: 2,5,
neural spine,
transmits the caudal artery and vein (§§ 157 and 158): a
median process, the hamal spine (4.5), is given off at
the junction of the hemal processes of most of the
vertebree, or may occur as a distinct cartilage (see Fig. 11).
13. The absence of inter-neural plates and of ribs.
14. The gradual reduction in size and simplification in
structure of the vertebrae, seen in passing from the anterior
to the posterior end of the caudal region.
15. The skeleton of the two dorsal fins, attached to
the posterior caudal vertebree: each consists of several
radial cartilages or fin rays, attached to two basal
cartilages, these latter being attached by fibrous tissue to
D
34 ZOOTOMY.
several contiguous neural spines. Connected with the
distal ends of the radial cartilages are numerous horny fila-
ments, the dermal fin rays, which support the distal
portion of the fins.
16. The skeleton of the caudal fin is rudimentary, con-
sisting of a few very small radial cartilages attached to the
posterior caudal vertebre: the fin is supported almost
entirely by dermal fin rays.
VI. In the brain-case, note
17. The flat floor (basis cranii, Fig. 10) and roof
(tegmen cranii).
Fic. 14——Raja nasuta, A caudal vertebra, seen from the front
(nat. size).
¢, centrum, 4.2, hemal process: 4.5, hemal spine: z.Z, neural
process : #.s, neural spine.
18. The foramen magnum, a large rounded aperture
on its posterior wall, placing the cranial cavity in communi-
cation with the neural canal of the vertebral column. The
cartilage surrounding the foramen magnum constitutes the
occipital region of the skull.
19. The occipital condyles, rounded protuberances,
one on either side of the foramen magnum, for articulation
with the corresponding surfaces on the anterior vertebral
plate: between them the base of the skull is scooped out
for the reception of the odontoid process.
20. The auditory capsules (Fig. ro, aw), large out-
standing masses of cartilage, one on either side of the
THE SKATE. 35
hinder or occipital region of the skull, and serving for the
lodgment of the organ of hearing.
21. In front of the auditory capsules—the interorbital
region—the cranium narrows considerably, but soon widens
out again to form
22, The nasal capsules (Fig. 10, o/), large outwardly
projecting masses of cartilage, containing a cavity for the
lodgment of the nasal sacs, which cavity is closed above,
but widely open below, and communicates with the cranial
cavity by a large aperture through which the olfactory nerve
(§ 179) passes (see § 32).
23. In front of the nasal capsules the skull narrows again
to form the long projecting rostrum (Fig. 10, 7), at the
sides of which the two thin rostral cartilages (7c) are
attached.
24. In the postero-inferior region of the auditory capsule
close to where it joins the occipital region, is an aperture
leading by a canal excavated in the wall of the auditory
capsule, into the cranial cavity, and serving for the transmis-
sion of the pneumogastric or vagus nerve (§ 214).
25. A smaller aperture in the capsule external to the
last: this gives exit to the glossopharyngeal nerve (§ 215).
26. Two considerable apertures in front of the auditory
capsule, where it joins the side wall of the skull: the upper
and larger of the two is for the transmission of the fifth or
trigeminal nerve, the smaller of the two, situated below and
sgmewhat behind the first, for the seventh nerve or portio
dura (§ 186).
27. On the upper surface of the auditory capsule, near
the middle line, is an aperture—that of the aqueductus
vestibuli—leading directly into the cavity of the capsule
(see § 213).
28. On the upper surface of the skull, between and in
D2
36 ZOOTOMY.
front of the auditory capsules, is a large oval space closed
by dense fibrous tissue; this is the posterior fontanelle.
29. Anterior to and between the nasal capsules is a
similar space, freely open in the prepared skull, the
anterior fontanelle.
30. In the side-wall of the skull, about midway between
the olfactory and auditory capsules, is the large optic
foramen for the transmission of the optic nerve (§ 183) :
almost immediately above this are several very minute
apertures through which the fourth nerve (§ 185) passes,
while behind it is a small foramen for the passage of the
third nerve (§ 184).
31. The nasal capsule is perforated by two canals just
where it joins the skull, one through its upper part for the
orbito-nasal nerve (§ 205), another through its lower part
for the palato-nasal nerve (§ 209).
32. By making a longitudinal vertical section of the
skull, or by removing its roof, the large olfactory
foramen is seen, leading from the cranial cavity into that
of the olfactory capsule, and giving exit to the olfactory
nerve (§ 179).
33. In the same section of the skull is shown a large
foramen—the internal auditory meatus—leading from
the cranial cavity to that of the auditory capsule, and trans-
mitting the auditory nerve (§ 186): a little posterior to this
is a small aperture by which the glossopharyngeal nerve
enters the auditory capsule to leave it by the foramen
already seen (§ 25, see also §§ 188 and 218): posterior to
this again is the inner aperture of the canal for the vagus
(§§ 24, 189, 219).
VIL. In the remaining loosely-attached portions of the
skull make out
34. The labial cartilages (Fig. 10, 7s, 1—4), of which
THE SKATE. 37
there are altogether four, in connection with the ventral
region of each olfactory capsule: the first (Jd. 1) supports
the corresponding flap of the fronto-nasal process (§ 64), the
second (/d, 2) lies in the fold of skin external to the naso-
buccal groove (§ 64), the third (2. 3) bounds the nostril
internally, and the fourth (7, 4) externally.
35. The antorbital (palatine) cartilage (Fig. ro,
ant), a thick rod, attached to the outer face of the olfactory
capsule, and curving outwards and backwards to join the
anterior prolongation of the pectoral fin.
36. The hyomandibular (Fig. 10, 4.7), a club-shaped
cartilage, articulating by its broad end with the infero-
external region of the auditory capsule, and passing down-
wards and forwards.
37. The spiracular cartilage (meta-pterygoid) (Fig.
10, sf), a semi-lunar plate, attached by ligaments above to
the auditory capsule and below to the inferior end of the
hyomandibular.
38. The upper jaw (Fig. 10, pg), formed by the
fibrous union in the middle line of the two pterygo-
quadrate cartilages, which together form a strong,
curved, transverse bar, connected at its extremities by
ligaments to the hyomandibular and spiracular cartilages.
Each end presents a smooth convex facet for articulation
with the lower jaw.
39. The lower jaw or mandible (Fig. 10, mcf),
formed by the fibrous union in the middle line of the two
Meckel’s cartilages; it closely resembles the upper jaw
in shape, and is articulated to it at its extremities. Both
upper and lower jaws are more strongly calcified than the
rest of the skull. ,
4o. The hyoid arch (Fig. 10, ey, chy, h.hy), a slender
rod of cartilage, attached dorsally to the postero-superior
38 ZOOTOMY.
angle of the hyomandibular by a band of fibrous tissue, the
inter-hyal ligament, and made up of three segments,
an epi-hyal (e.Ay) above, cerato-hyal (c¢./y’) next, and
hypo-hyal (4.47) below.
41. The five branchial arches (Fig. to), each of which
consists primarily of four segments, which are, counting from
above downwards, pharyngo-branchial, epi-branchial
(er), cerato-branchial (¢.é7), and hypo-branchial
(4.6r). The fourth and fifth pharyngo-branchials unite
with one another and with the fifth epi-branchial to form a
single cartilage: the first hypo-branchials (4.47.1) unite
with one another in the middle line, forming a slender
transverse bar of cartilage just posterior to the lower jaw:
and the fifth hypo-branchials (4.47.5) also unite with one
another to form a large basi-branchial plate, produced
anteriorly into two processes, and lying immediately dorsally
to the heart and ventral aorta.
VIII. In the shoulder girdle, note
42. The complete union of the two halves of the girdle
in the middle line below, and the attachment of each half
above to the median dorsal ridge of the anterior vertebral
plate (Fig. ro).
43. The three convex articular surfaces or glenoid
facets (Fig. 10, g/, 1—3), situated on the external surface
of each half of the shoulder girdle, and serving for the
attachment of the three chief divisions of the fin (see
§$ 46—48). The part of the girdle which lies to the dorsal
side of the glenoid facets is the scapular region (sc, s.s¢),
—that on the ventral side the coracoid region (¢7).
44. The three large apertures or fontanelles which
perforate the shoulder girdle: the anterior of these is
the scapulo-coracoid fontanelle (Fig. 10, s.cf): the
postero-superior, the scapular fontanelle, and the
THE SKATE, 39
postero-inferior one, separated from the preceding by a bar
of cartilage, the coracoid fontanelle (cf).
45. The separation from the remainder of the girdle of
that part which is immediately attached to the vertebral
column: this is the supra-scapula (Fig. 10, s.sc), a flat
quadrate plate, attached by fibrous tissue to the scapula
proper.
IX. In the pectoral fin, make out
46. The pro-pterygium (Fig. ro, 4.47), a long stout car-
tilage, articulated proximally to the anterior glenoid facet,
and passing forwards and slightly outwards: it is continued
forwards by a series of similar cartilages, of progressively
diminishing size, which extend in front of the olfactory
capsule, and one of which becomes connected with the
antorbital cartilage.
47. The meso-pterygitim (Fig. 10, ms.f7), a flat, com-
paratively small cartilage forming the central portion of the
attached part of the fin: it articulates with the middle
glenoid facet.
48. The meta-pterygium (Fig. 10, m¢¢), a similar
cartilage to the pro-pterygium, which articulates with the
posterior glenoid facet, and passes backwards and outwards:
it is continued backwards by a series of smaller cartilages,
which extend a little posterior to the pelvic girdle.
49. The fin rays, long jointed rods of cartilage, attached
at their proximal ends to the three chief divisions of the
fore-limb, and becoming very slender at their distal extremi-
ties: a few enter into direct connection with the shoulder
girdle, between the meso- and meta- pterygium.
X. In the pelvic girdle and fins, observe
50. The hip girdle, consisting of a stout ventral bar
(Fig. 10, £z) which sends off on each side a forwardly
directed pre-pubic process (fu) from the external
40 ZOOTOMY.
extremity of its anterior edge, and an iliac process (i)
directed upwards and backwards from the external extremity
of its dorsal surface.
st. The acetabular facets (Fig. 10, ac. 1, ac. 2), two
projecting convex articular processes on the extremities of
the hip girdle, the anterior being directed outwards, the
posterior backwards.
52. The basale metapterygii, a stout backwardly-
directed cartilage, articulating with the posterior acetabular
facet: it is continued by smaller cartilages to the posterior
point of the fin.
In the male this series of cartilages is directly continued into the
skeleton of the claspers (see § 57), which is composed of several
more or less calcified cartilages, some of them produced into sharp
processes of various forms.
53. The fin rays: the first four or five are attached to
the pelvic girdle, pass almost directly outwards, and support
the anterior lobe of the fin (§ 56); the first, or pre-axial
ray, is many times thicker than any of the others, and
articulates with the anterior acetabular facet: the remaining
fin rays are connected with the basale metapterygii, pass
outwards and backwards, and support the posterior lobe of
the fin.
B.—DIRECTIONS FOR DISSECTION.
XI. Verify the following external characters :—
54. The extreme depression of the body from above
downwards : its rhomboidal shape, the anterior angle of the
thomboid being formed by the snout, the lateral angles by
the points of the pectoral fins, and the posterior angle by
the root of the tail, which is slender, depressed like the
body in its anterior part, but compressed from side to side
posteriorly.
THE SKATE. 4t
In R. batis the angle of the extremity of the snout is acute, and the
lateral or pectoral angle slightly so: in R. clavata and R. maculata
the angle of the snout is obtuse and the pectoral angles nearly right
angles.
55. The immense pectoral fins, of a triangular shape,
the bases of the triangles extending from the anterior ex-
tremity of the snout to within a short distance of the base
of the tail, and their apices forming the lateral angles of the
rhomboidal body.
56. The pelvic fins, each of which lies in the angle
between the posterior end of the corresponding pectoral fin
and the root of the tail, and consists of two lobes, an ante-
rior outwardly-directed narrow one, and a posterior broader
one, produced backwards, parallel with the tail.
57. In the male, the claspers, elongated organs, each
presenting a groove along the outer edge, and strengthened
by a cartilaginous skeleton which projects into the cavity
of the organ in the form of sharp plates of various shapes.
58. The dorsal fins, two small median lobes near the
posterior end of the tail.
59. The caudal fin, a still smaller lobe, quite at the
extremity of the tail.
60. The characters of the integument: it is tough and
strong; greyish brown on the dorsal, white or grey on the
ventral side: in certain parts it is quite smooth and devoid
of scales, but in others is roughened by minute asperities or
by well-marked spines, both being the exposed portions of
the placoid scales, each of which consists of a button-
like bony’base imbedded in the derm, and of a thorn-like
enamelled portion, which projects through the epiderm on
to the surface of the body: these scales are best made out
by dissecting out one of the larger ones.
In R. batis the dorsal integument is dark olive-green or brown,
the ventral integument dark grey, with minute black dots marking the
42 ZOOTOMY.
apertures of the sensory tubes: the only large spines are on the tail:
the greater part of the skin is smooth.
In R, clavata, the skin is brown above, white below : the dorsal
surface of the whole body is covered with asperities often produced into
distinct spines : the latter are especially large near the eyes and in the
middle line of the back and tail: in the female especially, large spines
occur on both dorsal and ventral surfaces of the body.
In R. maculata the dorsal surface is brown with darker brown or
black spots, the ventral surface white: the skin is nearly smooth,
except on the tail and in the region of the eyes: in the male there is a
patch of large movable spines on each side of the head and on each
pectoral fin, both on the dorsal surface.
61. The mouth, a wide, transverse aperture on the
under surface of the head, supported by the strong upper
and lower jaws, which can be felt through the skin.
62. The teeth, forming a close pavement of small en-
amelled plates, produced in some cases into sharp spines.
In R. clavata the teeth are pointed in the male, flat in the female.
63. The nostrils, moderate-sized apertures, one on either
side of the under surface of the head, a little in front of
the mouth.
64. The fronto-nasal process, an escutcheon-shaped
fold of integument, extending from the posterior boundary
of the nostrils backwards towards the mouth, at either angle
of which it forms a rounded lobe, beset with fimbriz. This
lobe bounds internally, and converts into an incomplete
canal, a groove—the naso-buccal groove—which ex-
tends from the nostril to the angle of the mouth.
65. The branchial apertures, five valvular slits on the
ventral surface of the body, behind the mouth, those of
opposite sides approaching one another posteriorly.
? Behind the last pair of branchial apertures, on the skin covering the
ventral portion of the shoulder girdle, is a pair of slit-like depressions,
looking like an obliterated sixth pair of gill slits.
THE SKATE. 43
66. The vent, or cloacal aperture, a large opening
with tumid lips, near the root of the tail.
67. The abdominal pores (Figs. 18 and 19, pp. 55 and
57, @.~), small slits, one on each side of the middle line,
just posterior to the vent.
68. A strong bar—the ventral portion of the shoulder
girdle (Fig. 10, cr)—can be felt a little behind the last
pair of gill slits, and a similar bar—the pelvic girdle (pu)
—a little in front of the cloaca. Between these lies the
abdominal cavity, and in front of the shoulder girdle,
between the branchial apertures, is the position of the
pericardial cavity.
69. The eyes, on the dorsal surface of the head, just
over the mouth: they are greatly depressed from above
downwards, and have no eyelids.
yo. The spiracles, two considerable apertures, one
behind each eye: they communicate with the cavity of the
mouth. The front wall of the spiracle is covered with fine
ridges, which constitute the pseudobranchia, the remains
of an embryonic gill. This is supported by a plate of
cartilage which may be easily felt, called the spiracular
cartilage (§ 37).
71. The sensory tubes, seen best on the ventral sur-
face, as delicate, transparent, winding lines, arranged sym-
metrically on opposite sides of the body, just beneath the
skin, on the surface of which they open by minute apertures.
XII. Make a median longitudinal incision, first through
the skin, then through the underlying muscle, from
the posterior edge of the shoulder girdle to the
anterior edge of the hip girdle : make transverse
incisions from both ends of this, and reflect the
flaps of skin and muscle, so as to expose the
abdominal cavity. Make out the following :—
44. ZOOTOMY.
72. The peritoneum, a shining pigmented membrane
lining the abdominal cavity and investing the viscera: from
it is secreted the larger or smaller quantity of peritoneal
fluid contained in the cavity.
73. The large, soft, trilobed liver, attached by a broad
base at the anterior part of the abdominal cavity, to the
hinder boundary of which its lobes extend; in colour it
varies from light brown to dark olive green.
74. The stomach, largely concealed by the middle and
left lobes of the liver, and passing towards the posterior side
of the abdominal cavity, where it becomes narrowed and
bent upon itself in a U shape.
7s. The intestine, partly hidden by the right lobe of
the liver; it is wider than the stomach and marked
externally with a spiral groove.
76. The cloaca (Figs. 18 and 19, ¢/), connected with the
posterior end of the intestine and situated quite in the
posterior part of the cavity: it is much larger in the female
than in the male. To bring it clearly into view it is advis-
able to remove carefully the median portion of the pelvic
girdle.
77. The spleen, a dark red lobulated body, situated
between the limbs of the U-shaped stomach.
78. The pancreas, a firm whitish gland, consisting of two
lobes, a large dorsal lobe, closely applied to the left side of
the intestine and connected by a bridge of gland substance
with the small ventral lobe, which lies to the ventral side
of the junction between stomach and intestine.
79. In adult specimens, more or less of the testes (Fig.
18, 4) (in the male) or of the ovaries (Fig. 19, ov) and
oviducts (od) (in the female) will be seen without dis-
turbing the other organs, at the sides of the abdominal
cavity, on the dorsal side of (beneath in their present
THE SKATE. 45
position) the foregoing viscera: they should be brought
into view by turning over the latter.
80, The kidneys (Figs. 18 and 19, 4) are also seen
when the other viscera are turned aside, as long, dark red
bodies, lying one on either side of the middle dorsal line
of the posterior end of the body cavity: they are often
obscured by the thick pigmented peritoneum which covers
them.
XIII. Make a median longitudinal incision from the
anterior boundary of the shoulder girdle to about
the level of the second gill cleft: take transverse
incisions from both ends of this, and reflect the
flaps made, so as to expose the pericardial cavity :
note
81. The strong fibrous partition bounding the _peri-
cardium posteriorly, and separating it from the abdominal
cavity. .
82. The heart (Figs. 17, 20, and 21), consisting of a
fleshy ventricle (v), from which is given off anteriorly,
and somewhat to the right side, the fleshy tubular conus
arteriosus (ca) ; and to the dorsal side of these (beneath
in this position) the large thin-walled sub-triangular auricle
(az), and posterior to this, the transverse, tubular, transparent
sinus venosus (5.7).
XIV. Remove the skin to a distance of about an inch
on either side of the heart, so as to expose the
gill-sacs: remove the ventral walls of the latter,
so as to expose their cavities. Make out
83. The five pairs of gill cavities, separated from one
another by complete partitions, and opening externally by
the apertures already seen.
84. The red branchial filaments attached to both
anterior and posterior walls of all the cavities except the
46 ZOOTOMY.
last, the posterior face of which is devoid of them. Each
set of filaments is a demibranch or half-gill: each
partition with its pair of demibranchs constitutes a gill.
It will be seen that there are four complete gills, and one
odd half-gill forming the first of the series.
XV. Make an incision through the skin of the head,
about an inch in front of the eyes, Ze. in the
region of the anterior fontanelle: lifting up the
edge of the incision, so as to see what you are
about, cut away the roof of the skull and the
overlying skin, until the brain and the anterior
part of the spinal cord are exposed. If no other
specimen is to be dissected, go over §§ 169—189 ;
then remove the brain by cutting through the
nerves and place it in strong methylated spirit.
If a special dissection of the nervous system is to
be made, remove to spirit at once,’ first noting
85. The dura mater, or membrane lining the cerebro-
spinal cavity, in which the brain and spinal cord he.
86. The pia mater, a delicate membrane investing
the brain and cord and containing numerous _blood-
vessels.
87. The arachnoid fluid contained in the cerebro-
spinal cavity.
88. A mass of gelatinous tissue filling up the anterior part of the
cerebral cavity.
1 For the satisfactory dissection of the brain, it is necessary for it to be
placed in spirit while fresh ; it is therefore advisable for the student to
reach this stage of the dissection by the end of the first day’s work. Fora
permanent preparation, the brain should be placed for 24 hours ina
saturated solution of zinc chloride, and then, after removal of the pia
mater, into strong alcohol, which should be changed at least once
(Giacomini’s method): the brain, either separate or 77 stfu, may then
be prepared by the glycerine jelly process (p. 2, § 1).
THE SKATE, 47
XVI. Place the animal with the ventral side upwards,
turn the lobes of the liver forwards so as to
expose the remaining abdominal viscera, and
without cutting or tearing anything, make out the
following points :—
89. The relations of the various parts of the alimentary
canal: the cesophagus or gullet enters the abdominal
cavity through its anterior wall, to the dorsal side of the
liver, and almost immediately dilates slightly to form the
stomach: this passes to the posterior boundary of the
abdomen, becomes narrowed, turns upon itself, and passes
forward to about the middle of the cavity, where it forms a
thickening—the pylorus—and becomes continuous with the
intestine: this is, in its anterior or proximal portion,
devoid of the spiral groove mentioned in § 75, and loses
it again in its posterior or distal part, shortly before it
passes into the dilated cloaca: the anterior smooth
portion of the intestine may be called the duodenum,
the middle, dilated, spirally-marked portion the colon,
and the posterior smooth portion the rectum: to the
latter is attached, dorsally, a small conical red body, the
rectal gland.
go. The mode of attachment of the alimentary canal.
The posterior part of the oesophagus and anterior part of
the stomach are suspended to the dorsal wall of the abdo-
minal cavity by a fold of peritoneum, the mesogaster:
the rectum is similarly suspended by a second fold, the
mesorectum. The greater part of the intestine, on the
other hand, is entirely unsuspended, so that there is no
mesentery proper.
gt. The fold of peritoneum—gastro-hepatic omen-
tum—which passes between the liver and stomach, and is
joined near the latter by a similar but much longer fold, the
48 ZOOTOMY.
duodeno-hepatic omentum—from the duodenum. In
these folds are contained the various vessels passing to the
liver (§ 93).
92. The attachment of the spleen to the dorsal wall of
the stomach by a broad sheet of peritoneum, the gastro-
splenic omentum.
93. The vessels! contained in the duodeno-hepatic
omentum, to see which the membrane should be put
somewhat upon the stretch. These are the bile duct
(Fig. 15, ¢0.@) to the animal’s right side, the duodenal
1 For the satisfactory dissection of the blood-vessels the fish should be
injected : if not, they may be made out by inflating with air by means
of an anatomical blowpipe. I find the following the most convenient
method for injection. Have ready four of the movable cannule usually
provided with injecting syringes, or if these are not at hand, four glass
tubes drawn out to the form shown in the annexed cut: the end a is
for insertion in the vessel, the constriction & for the
purpose of preventing any slipping of the ligature,
over the end ¢ a short piece of india-rubber tubing is
placed, and into this the nozzle of the syringe is pushed.
Make a small incision into the conus arteriosus, place
one cannula in it, directed forwards, and tie it firmly
in its place: tie the second, directed outwards, into
the sinus venosus: the third, directed forwards (ze.
towards the dorsal aorta), into the duodenal artery: the
fourth, also directed forwards, into the duodenal vein.
Fill an ordinary tumbler half full of fine plaster of Paris,
coloured with a little of the common ‘‘ French blue” cr ultramarine
of the oil shops: fill up the tumbler with water, stir well and
immediately strain the liquid through coarse muslin into a second
tumbler. Fill the syringe, and inject through all four cannulz suc-
cessively. This must be done very rapidly or the plaster will set. On
removing the syringe from a cannula, the india-rubber tube should
be plugged with a small piece of wood to prevent escape. All the
chief vessels are injected in this way : the ventral aorta and its branches
from the conus, the systemic veins from the sinus venosus, the dorsal
aorta and its branches from the duodenal artery, and the portal vein
form the duodenal vein. The caudal and renal portal veins have to be
THE SKATE, 49
and superior mesenteric arteries (Fig. 20, d, s.m) towards
the left, and the wide thin-walled portal vein (Fig. 16, 9)
between them,
Running parallel with these vessels is also 2 transparent thin-walled
lymphatic vessel, from which many of the chief lymphatics can be
injected.
94. The gall bladder (Fig. 15, 2.4), a greenish or
yellowish transparent sac, partly imbedded in the liver
between its right and middle lobes.
Fic. 15.—Raja nasuta, The gall bladder and bile ducts (half nat.
size),
ae common bile duct: ¢.d, cystic duct: g.d, gall bladder: /.4.d,
left hepatic duct : 7.4.d, right hepatic duct.
XVII. Carefully dissect away the peritoneum from the
bile duct: make a small aperture in its wall, in-
troduce a blowpipe and inflate: the gall bladder
will be distended : trace the duct in both directions
and make out
done separately: the femoral and ilio-hemorrhoidal veins also often
escape being filled. Ina preparation for demonstrating purposes it is
advisable to colour the plaster of Paris used for injecting the dorsal '
aorta with vermilion or carmine instead of French blue,
E
5° ZOOTOMY.
95. Its passage anteriorly into the gall bladder, by the
short cystic duct (Fig. 15, ¢d).
96. Its entrance posteriorly into the duodenum, im-
mediately behind the pylorus on the dorsal side. A bristle
should be passed into the duodenum through the cut end
of the duct.
97. The junction with it of the two hepatic ducts, one (Fig. 15,
1.4,.d) from the middle and left lobes, the other (7.4.d) from the right
lobe of the liver : the latter enterf the common bile duct close to its
junction with the liver, so that the cystic duct (¢.@) is very short.
XVIII. Dissect away the peritoneum from the pancreas, and
make out
98. The pancreatic duct, passing from the ventral lobe of the
gland to open into the ventral wall of the duodenum, almost exactly
opposite the entrance of the bile duct.
XIX. Dissect away the peritoneum from the blood
vessels mentioned in § 93, and trace them in both
directions, turning the stomach over to the left to
see the origins of the arteries. Note
99. The portal vein (Fig. 16, 4), passing towards the
middle lobe of the liver, and sending off branches to all
three lobes.
It is constituted distally by a gastric vein (g), which receives the
blocd from the stomach, and by a mesenteric vein (du, sf/, pn, 7),
which receives the blood from the intestine, spleen, and pancreas.
100. The ceeliac artery (Fig. 20, cz), entering the
abdominal cavity on the dorsal side of the cesophagus and
dividing into two trunks, one of which, the gastro-hepatic
artery, sends off a hepatic artery (7) to the liver and
a gastric artery (g) to the stomach, while the second or
duodenal artery (d) passes down the duodeno-hepatic
omentum, and supplies the greater part of the duodenum
and the pylorus.
THE SKATE. 51
ror. The superior mesenteric artery (Fig. 20, s.m)
entering the abdominal cavity parallel with, and a little
posterior to the cceliac.
It divides into two main branches, one of which supplies the intestine
(7), the other the pancreas (47) and spleen (s#/). The rectum is
mainly supplied by the small inferior mesenteric artery (§ 157, Fig.
20, 7,m), which passes directly from the aorta to the rectal gland.
Fic. 16,—Raja nasuta. The portal vein (one-third nat. size).
du, duodenal vein: g, gastric vein: 2, intestinal vein: #, main trunk
of portal vein : 4, pancreatic veins: sf/, splenic vein.
1oz. The ramifications of the gastric branch of the
pneumogastric nerve on the walls of the stomach (see
§ 214).
XX. Turn the liver into its natural position again, and
remove just sufficient of the shoulder girdle to
bring into view
103. The hepatic sinus (Fig. 17, 4.s),a large transverse
vessel, lying across the ventral surface of the cesophagus,
immediately in front of the anterior border of the liver: it
receives the hepatic veins by which the blood is returned
from the liver.
104. The anterior extremities of the oviducts (Fig. 19,
jit) in the female, or the rudimentary pronephric ducts
E 2
52 ZOOTOMY.
in the male (Fig. 18, pv.d, see §§ 117 and 118) The
former are attached to the dorsal (under, in the present
position,) surfaces of the shoulder girdle by a distinct
ligament.
XXI. Remove the liver, taking care not to injure
the hepatic sinus or oviducts: cut through the
stomach just beyond its junction with the ceso-
phagus: cut through the rectum just anteriorly to
the rectal gland: remove the alimentary canal
between these two points,
Wash out the contents of the alimentary canal by directing a stream
of water through it, then fill with ao’5 per cent. solution of chromic
acid, by tying one end, pouring in the acid through a small funnel or
injecting it with a syringe, and when full, tying the other extremity :
place in a vessel of the same solution for a few days: when sufficiently
hardened, cut windows in various parts and make out
105. The pyloric valve, a fold of mucous membrane extending
between the stomach and intestine, and opening towards the latter.
106, The spiral valve, commencing in the duodenum as a simple
inwardly-directed fold of the mucous membrane, and in the colon
becoming a spiral inclined plane which finally terminates at the com-
mencement of the rectum. The development of the spiral valve varies
almost indefinitely: its width may be either less than, equal to, or
greater than the semi-diameter of the gut: the plane of any part of it
may be either at right angles to the long axis of the intestine, or in-
clined to it in either direction. There is also much variation in the
number of turns of the spiral and in the character of the mucous
membrane.
107. ‘Lhe irregularly longitudinal ridges or ruge of the stomach.
108. The network of fine ridges, covering the interior of the intestine
and the spiral valve.
XXII. If the fish is not injected, make a small aperture in the
sinus venosus, introduce « blowpipe directed outwards, and
inflate.
109. If nothing has been cut, a large inflated sac will be seen in the
middle of the abdominal cavity, between the genital glands : this is the
great cardinal sinus (Fig. 17, ca.s), formed by the union in the
middle line of the two posterior cardinal veins (cd), by which the blood
Fic. 17,—Raja nasuta. The venous system, ventral aspect (one-
third nat. size).
The portal vein is not shown ; the renal rortal vein (7A) is supposed
to be removed on the right side (left in the figure), and the femoral
(fm), ilio-hemorrhoidal (77.4), &c., veins as well as part of the car-
dinal (cd) on the left. ‘The right precaval sinus (c.s) is cut open,
so as to show the apertures in its walls, The cutlines of those portions
of the auricle (az) and sinus venosus (s.v) which lie behind (dorsal
to) the ventricle (v), are dotted.
ab, veins from abdominal walls: az, auricle: 5.2, bulbus anteriosus :
br, brachial vein: ¢, caudal vein: ¢.a, conus arteriosus: cd, cardinal
vein : cd.’, posterior anastomosis of cardinal veins : ¢d.s, cardinal sinus :
epg, epigastric vein: fm, femoral vein: 4.5, hepatic sinus : 42, heemor-
rhoidal veins: 7.4, ilio-heemorrhoidal vein: 77x, inferior jugular
vein : jz, jugular vein: /y, opening of lymphatic trunk into precaval
sinus: #¢.s, precaval sinus: 7.g, renal portal vein: ».9’, factors of
renal portal vein from pelvic and lumbar regions: 7p”, branches of
renal portal veins entering kidney: sf.s, spermatic sinus: s.v, sinus
venosus : v, ventricle.
54 ZOOTOMY.
is brought back from the tail, kidneys, genital ergans, cloaca, rectum,
pelvic fins, &c. These veins run along the inner side of the kidneys
(see § 130), and enter the sinus at about the anterior extremity of those
glands : leaving the sinus, the cardinal veins are continued forwards
and curve round the gullet to join the precaval sinus (fc.s) : they are
best seen at a future stage.
XXIII. The following organs are also best observed at
this stage :—
t10. In the male, the testes (Fig. 18, #), irregularly oval
bodies, closely connected with the venous sinus, one on
either side. In the adult they have a flat ventral and a
rounded dorsal surface: the former has a granular appear-
ance, the latter is beset with small rounded elevations. In
the young condition the whole surface is quite soft and
granular. At its anterior end, even in the adult, the testis
is soft and thin, and passes into the upper end of the
epididymis (see § 114) by which its secretion is carried
off.
111. In the female the ovaries (Fig. 19, ov): these in
the young condition are indistinguishable from testes, but in
the adult state aré covered with elevations varying from the
size of the yolk of a hen’s egg downwards—the Graafian
follicles. Note the absence of any duct in direct con-
nection with the ovary, the ova having to pass into the
peritoneal cavity before reaching the aperture of the ovi-
ducts.
112. The fold of peritoneum called mesorchium in
the male, mesoarium in the female, by which the genital
glands are supported.
XXIV. Remove the genital glands and the venous
sinus, and very carefully dissect away the perito-
neum from the organs still left in the abdominal
cavity, noting
113. The kidneys (Figs. 18 and 19, 2), flat, reddish
THE SKATE, 55
Fic. 18.—Raja batis. The urinogenital organs of the male (one-
third nat. size).
The organs are supposed to be removed from the body along with a
small portion of the cesophagus (¢s), and viewed from the ventral aspect :
the right testis (¢) is removed, along with the corresponding epididymis
(epd) and all but the posterior extremity of the vas deferens (v.¢),
which, with the sperm sac (s.s) is turned outwards to display the
ureters (ur): the cloaca (¢/), the urinogenital sinus (mg.s), and the
right vesicula seminalis (v.s) and sperm sac (s,s) are laid open.
a.p, abdominal pore: ci, cloaca. epd, epididymis: 7.7, inter-renal
body: 4, kidney: @s, cesophagus: fx.d, pronephric duct: s.s, sperm
sac: s.s’, its opening into the urinogenital sinus: 4, testis: wg.f, urino-
genital papilla: ug.s, urinogenital sinus: wr, ureter: 27’, its opening
into the urinogenital sinus: v.d, vas deferens: v.s, vesicula seminalis :
v.#, its opening into the sperm sac.
56 ZOOTOMY.
brown, lobulated bodies, lying close to the dorsal wall of
the abdominal cavity, and covered, on their ventral surfaces
only, by peritoneum.
Ln the male.
114. The epididymes (Fig. 18, efd), long flat, whitish
bodies overlapping the anterior part of the kidneys, and con-
tinued forwards to the front boundary of the abdominal cavity.
The greater part of the epididymis (mesonephros or paror-
chis) has a granular appearance, and its actual tubular
structure is only seen in microscopical examination, but on
its ventral surface it is very evidently made up of a greatly
convoluted tube, which becomes more distinct and less con-
voluted near the posterior boundary of the parorchis, where
it passes into
115. The vas deferens (Fig. 18, v.@), mesonephric
duct, or duct of the testis, a convoluted tube passing back-
wards from the hinder end of the epididymis, towards the
posterior boundary of the abdominal cavity, where it
becomes dilated.
116. The sperm sacs (Fig. 18, s.s), large whitish ovoidal bodies,
in the posterior region of the abdominal cavity, and immediately
external to the posterior dilated portion of the vasa deferentia, from
which they are separated externally by so slight a groove as not to te
readily distinguishable from them. They are seen to advantage only in
fully adult specimens.
117, The coalesced remnants of the Miillerian or pronephric
ducts (Fig. 18, #7.d), consisting of a fine thin-walled tube, situated
on the ventral wall of the hepatic sinus, where it dies away at
each side, and opens in the middle line by a small aperture homo-
logous with the peritoneal opening of the oviducts in the female
(see § 118).
Ln the female.
118. The oviducts (Fig. 19, 7.4 wt), each of which
consists of two parts : a posterior, wide, thick-walled uterine
THE SKATE. 57
portion (ut), opening into the cloaca, and an anterior,
slender, thin-walled portion, or Fallopian tube (/.4)
which unites with its fellow of the opposite side on the
Fic. 19.—Raja batis. The urinogenital organs of the female (one-
third nat. size).
The organs are removed from the body along with a small portion of
the cesophagus (@s), and are viewed from the ventral aspect. The left
ovary (ov) is removed as well as the greater part of the right oviduct ;
the cloaca and the right horn of the urinary bladder are laid open.
ap; abdominal pore: ¢/, cloaca: /7.¢, Fallopian tube, or anterior
portion of oviduct : #,/’, common opening of the conjoined Fallopian
tubes into the abdominal cavity: 4, kidney: mz.d, mesonephric duct :
od.g, oviducal gland : @s, cesophagus: ov, ovary : w.4, urinary bladder:
u.p, urinary papilla: wr, ureters: wé, uterine portion of oviduct :
wt’, its opening into the cloaca.’
58 ZOOTOMY.
ventral surface of the gullet, where the two tubes have a
common oval opening (77) into the peritoneal cavity.
At the anterior end of the uterine portion of the oviduct is
a large, solid, reniform body, of a whitish hue, imbedded in
its walls: this is the oviducal gland (od.g), and secretes
the horny “purse” in which the eggs are laid: it is not
developed in very young specimens. —
rig. The urinary bladder (Fig. 19, 1.4) a bilobed
sac with thin membranous walls, situated between the
posterior ends of the oviducts: it will be better seen after
distension with air (see § 123).
X XV. Open the cloaca by a median incision along its
ventral wall, and note in it
120. The opening of the rectum.
Ln the mate.
121. A small, thin-walled tube, the urinogenital papilla
(Fig. 18, gf), projecting from the dorsal wall of the
cloaca. By inserting a blowpipe into this and inflating,
the sperm sacs and vasa deferentia will be dilated.
in the female.
122. The large, thick-lipped apertures of the oviducts
(Fig. 19, wz), one on each side of the anterior region of
the cloaca. In young specimens each of these is closed by
a fold of the mucous membrane, the hymen.
123. A small conical elevation, the urinary papilla
(Fig. 19, w#.£), situated between the oviducal apertures and
having at its apex a small opening ; by inserting a blowpipe
into this and inflating, the urinary bladder will be
distended.
Ln the male.
XXVIL_ Slit up the urinogenital papilla, cutting along a probe or
1 The following points (§ 124—127) can only be made out to advantage
in fully adult specimens.
THE SKATE. 59
blowpipe passed into it, and taking care not to go too far,
The papilla will be found to lead into
124. The urinogenital sinus (Fig. 18, zg.s), a small cavity attached
to the dorsal wall of the cloaca, into which it opens by the urinogenital
papilla: at its anterior extremity will be seen two pairs of apertures,
one pair (s.s’) ventrally situated, round, and opening into the sperm
sacs, the other pair (z7“) dorsally situated with regard to the first,
partly hidden by the projection into the sinus of the sperm sacs, of a
somewhat crescentic form, and leading into the ureters (§ 128).
XXVII. Remove all that is left of the rectum, and of that part of
the cloaca anterior to the urinogenital sinus: slit open the
sperm sacs along their ventral wall ; note
125. The greenish epithelium lining the sperm sacs, and the greenish
viscid fluid which fills them, and which consists of semen mixed with
the secretion of the sacs.
126, A crescentic, thick-lipped aperture (Fig. 18, v.s’), on the dorsal
wall of each sperm sac, just within (anterior to) the opening of the sac
into the urinogenital sinus : this aperture leads into the vas deferens.
XXVIII. Open the lower part of the vas deferens and note
127. Its expansion posteriorly into « chamber—a sort of vesicula
seminalis (Fig. 18, v.s), which has its walls produced into lamine,
dividing its cavity into a number of compartments ; at its posterior end
this dilatation of the vas deferens opens into the sperm sac by the
crescentic aperture already noticed.
XXIX. Carefully dissect one or both of the vasa
deferentia from the surrounding parts, and either
remove it entirely or turn it over to one side.
Make out
128. The ureter (metanephric duct, Fig. 18, wr), a
delicate, colourless tube, situated close to the inner edge of
each kidney ; it is made up by lesser tubes proceeding from
the several lobes of the kidney, and passes backwards to
open into the urinogenital sinus by the slitlike aperture
already noticed.
129. The inter-renal (Fig. 18, 27), a long, irregular
body of a yellow colour, lying just to the inner side of the
ureter.
60 ZOOTOMY.
The true adrenals or supra-renal bodies are small yellow masses in
connection with the sympathetic g ganglia.
130. The cardinal veins (Fig. 17, c@) lying to the ventral side of
the ureters, receiving veins from the hidneys, uniting with one another
posteriorly by a transverse anastomosis, and passing forwards to enter
the cardinal sinus (§ 109).
131. The dorsal aorta (Fig. 20, d.ae), a delicate artery
lying in the middle line between the kidneys, to which it
sends branches. (See $157).
XXX. Dissect away the skin from the ventral face of one of the
pelvic fins, and make out
132. The gland of the clasper, consisting cf a large ovoidal sac
with thick muscular walls, which leads by a widish passage at its
posterior end into the cavity of the clasper, and which receives the
secretion of the gland itself. This is seen by cutting away the ventral
wall of the sac to consist of two lobes, with a longitudinal groove
between them, in which are the numerous papilliform terminations of
the efferent ducts.
Ln the female.
XXXI. Turn over one of the oviducts and the corre-
sponding half of the cloaca to the opposite side of
the body, so as to expose one of the kidneys:
dissect out—
133. The ureters (Fig. 19 wv), delicate tubes proceeding
from the inner edge of the kidney: those coming from the
anterior part of the gland pass backwards, those from its
posterior part forwards, towards the dorsal wall of the
urinary bladder, which they enter.
134. A delicate thread proceeding forwards from each
horn of the bilobed bladder, and presenting slight enlarge-
ments at intervals: this is the parovarium (Fig. 19, m7.d)
the rudiment of the anterior part of the Wolffian body or
mesonephros of the embryo, and answering to the parorchis
in the male.
XXXII. Remove the ventral wall of the urinary bladder, and ncte
THE SKATE, 61
135. The three or four minute apertures on each side of the dorsal
wall of the bladder, by which the ureters open.
136. The adrenals, inter-renals, dorsal aorta, and cardinal
veins, which have the same relations as in the male (§§ 129-
131).
Ln both sexes.
XXXIII. Carefully dissect away the muscular tissue
immediately anterior to the heart and between the
two sets of gills, and make out
137. The synangium or bulbus arteriosus (Figs. 20
and 21, 4.2), a white dilatation, connected with the anterior
end of the conus arteriosus or pylangium (ca, § 82), and
giving off three vessels, one anteriorly, the ventral aorta
(v.a0), and one on each side, the posterior innominate
arteries (f.77). The ventral aorta passes forwards to the
level of the anterior gill cavity, and there divides into two
vessels, the anterior innominate arteries (a./z) which
are given off at right angles to the ventral aorta, one on
either side. Each anterior innominate artery soon divides
into two trunks, each posterior innominate into three ; these
five vessels are
138. The afferent branchial vessels (Figs. 20 and 21,
' a.br, 1—5), each of which goes to one of the plates by
which the gill cavities are separated from one another, passes
from the ventral to the dorsal extremity of the plate, external
to the branchial arch (see § 166), and gives off branches to
the gill filaments.
139. The hypobranchial artery (Figs. 20 and 21, Ay.dr), running
antero-posteriorly, just internal to the gills, and crossing the afferent
branchial arteries : it springs from the brachial artery (§ 157), anastomoses
with the efferent branchial arteries (§ 156), and, besides supplying the
tissue ofthe gills, sends off an anterior coronary artery (Figs, 20 and
21, a@.co) to the conus arteriosus and ventricle, and a posterior
coronary (.co), to the sinus venosus.
62 ZOOTOMY.
Fic. 20,—Raja nasuta. The arterial system, seen from the ventral
aspect (one-third nat. size).
The heart and ventral aorta (v.ao) are slightly displaced towards the
right side (left in the figure): the left afferent branchial arteries (2.7)
are removed, and the right efferent branchials (¢.67): the lett efferent
branchials are straightened out, so as to bring their ventral ends to the
THE SKATE, 63
extreme right of the figure: the left hypobranchial artery is also
displaced outwards ; that of the right side (left in the figure) (Ay.67)
is drawn zz site,
a.br, I, first, and adr. §, last afferent branchial artery: a.co, anterior
coronary artery : a@.7#, anterior innominate artery: 4.a, bulbus arterio-
sus: 67, brachial artery: ¢, caudal artery: c.a, conus arteriosus:
¢.¢, common carotid artery: ca, coeliac artery: d@, duodenal artery :
dao, dorsal aorta: e¢.ér. 1, first, and er. 9, last efferent branchial
artery : ¢.c, external carotid artery ; 7, artery to fronto-nasal process :
g, gastric artery: , hepatic artery: Ay, hyoidean artery: hy.dr,
hypobranchial artery: 2, intestinal artery : z.c, internal carotid artery:
z/, iliac artery: 7., inferior mesenteric artery: mm, artery to man-
dible: 7.67, nutrient arteries of the gills: od, oviducal arteries: f.co,
posterior coronary artery: f.7, posterior innominate artery: pv,
pancreatic arteries: 7, renal arteries: s, artery to snout: s.c/, sub-
clavian artery: 5.72, superior mesenteric artery: s#/, splenic artery :
spm, spermatic artery: v, ventricle: v.a0, ventral aorta: v7, vertebral
artery.
140. The inferior jugular vein (Figs. 17 and 21, 7.7) situated in
the dorsal wall of the pericardium, near its outer border: it brings
blood from the floor of the mouth and pericardial walls, and enters the
precaval sinus (§ 149, Figs. 17 and 21, fe.s).
aco | hybr peo
Fic. 21.—Raja nasuta. Diagram of the heart and chief blood-
vessel, from the left side (half nat. size). : :
a.br. 1, first, and a.ér. 5, last afferent branchial artery : @.co, anterior
coronary artery: az, auricle: d7.a, brachial or subclavian artery :
br.v, brachial vein: ¢.a, conus arterlosus : ed, cardinal vein: @.ao,
dorsal aorta; ¢.6. I, first, and ¢47. 9, last efferent branchial artery :
h.s, hepatic sinus : 2y, hyoidean artery: hy.6r, hypo-branchial artery :
2.ju, inferior jugular vein : 72, jugular vein: 7.dr, nutrient arteries o
the gills: Z.co, posterior coronary artery: c.s, precaval sinus: 5.v,
sinus venosus : v, ventricle : v.ao, ventral aorta.
‘
64 ZOOTOMY. -
141. The thyroid gland, a flattened rounded body, of
a deep red colour, situated immediately in front of the
anterior end of the ventral aorta.
XXXIV. Cut through the ventral aorta and posterior innominate
arteries close to the bulbus arteriosus, and turn the heart
backwards, so as to expose the pericardial cavity. Note
142, An aperture in the centre of the posterior dorsal region of the
pericardium : by passing a probe into this it will be found to lead into
a funnel-shaped cavity which soon divides into two membranous canals.
‘Ybese—the pericardio-peritoneal canals—pass backwards along the
ventral wall of the gullet, and open each by a widish aperture, thus
placing the pericardium in communication with the peritoneal cavity.
XXXV. Remove the heart entirely, by cutting through
both ends of the sinus venosus and the membrane
by which it is united to the pericardium: make
out carefully the relations of the various parts of
the heart (§ 82), then cut open, first the auricle and
sinus venosus from the dorsal side, and afterwards
the ventricle and conus arteriosus from the ventral
side. Make out
143. The thin, smooth walls of the sinus venosus.
144. The thin walls of the auricle, strengthened by a
complicated network of muscular fibres, the musculi
pectinati.
145. The large sinu-auricular aperture guarded by
the two membranous flaps of the sinu-auricular valve.
146. The circular auriculo-ventricular aperture,
guarded by the two long flaps of the auriculo-ventricular
valve, which are attached round the margins of the aper-
ture, and hang down into the ventricle.
147. The small, horseshoe-shaped cavity of the ventricle,
and its immensely thick walls, strengthened internally by
muscular ridges or columne carnez.
148. The three longitudinal rows of aortic valves in
THE SKATE. 65
the conus arteriosus, each row containing five somewhat
semilunar flaps, opening towards the synangium.
XXXVI. Pass a probe, directed outwards and backwards, into
either of the cut ends of the sinus venosus: carefully cut away
the cartilage of the shoulder girdle and other tissues until the
end of the probe is brought into view: it will be found to
have passed into
149. A small chamber, the precaval sinus (Figs. 17 and 21, gc.s),
situated in the antero-lateral angle of the abdominal cavity. In its
wall are several apertures : one, situated antero-internally, is the opening
of the jugular vein (7), by which the blood is returned from the
head: another, postero-internal in position, is the opening of the
cardinal vein (cd) already seen: a third, on the ventral wall of the
sinus, puts it in communication with the hepatic sinus.(4.s) : a fourth,
at its anterior end, leads into the sinus venosus (s.v) : a fifth, very
small, just internal to the last, into the inferior jugular vein (2.ju) : a
sixth, on the outer wall, into the brachial vein (47) and lastly, in
the middle of the dorsal wall, is a transverse aperture, guarded by two
valves, by which the contents of the chief lymphatic trunk (Fig. 17,
dy) axe poured into the sinus.
150. A sympathetic ganglion (see § 220), a whitish elongated body
about a quarter of an inch long, will be found immediately outside the
inner wall of the sinus.
XXXVII. Cut away the remainder of the ventral
portion of the shoulder girdle, and cut through
the floor of the mouth, by making an incision a
little to one side of the median line so as not to
injure the ventral aorta, through the cesophagus
and basibranchial plates (see § 41), and through
both jaws. Fasten back the two halves of the
mouth-floor thus separated, so as to expose the
whole oral cavity from beneath. Note
1st. The internal branchial clefts, five long vertical
fissures, by which the gill pouches communicate with the
cavity of the mouth.
152. The opening of the spiracle into the mouth, just in
front of the first gill cleft.
F
66 ZOOTOMY.
153. The curved hard bars which separate the gill clefts
from one another: these are the branchial arches.
154. A similar hard bar of cartilage separating the spiracle
from the first gill cleft: this isthe hyoid arch.
155. The relations of the branchial filaments to the bran-
chial arches: there is a set of filaments on both the anterior
and posterior walls of all the gill cavities except the last, the
posterior wall of which is devoid of filaments. Thus there
are nine sets of filaments or half-gills in all, one of which
occurs on the posterior face of the hyoid arch, and one on
each face of each of the first four branchial arches, the fifth
branchial arch being without filaments.
XXXVIIIL. Carefully dissect away the mucous mem-
brane from the roof of the mouth; remove the
dorsal ends of the gill arches or pharyngo-bran-
chials ; and follow out
156. The efferent branchial arteries (Figs. 20 and
21, ¢.6r. 1—g), of which there are nine, one for each demi-
branch: after leaving the dorsal ends of the gills they unite
with one another in pairs, that from the hyoidean demi-
branch uniting with that from the anterior demibranch of
the first branchial arch, that from the posterior demibranch
of the first with that from the anterior demibranch of the
second branchial arch, and so on. Four trunks are thus
formed, the last of which receives the vessel from the
posterior demibranch of the fourth branchial arch, and the
first two of which soon unite with one another, so that there
are now three main efferent branchial trunks on each
side. These takea direction inwards and backwards. The
most anterior of the three pairs unite with one another in
the middle line and form a short trunk: with this the next
pair unite and produce a somewhat larger trunk, with which,
finally, the third pair join. The longitudinal vessel thus
THE SKATE. 67
formed by the union of the efferent branchial trunks is the
dorsal aorta (§ 157).
The efferent branchial arteries unite with one another in the way
described at their ventral as well as at their dorsal ends, thus forming
complete loops, the spaces enclosed by which correspond to the bran-
chial clefts. The two arteries of each complete gill are united with one
another by a cross branch at about the middle of their length: it is
through this anastomotic branch of the last gill that the ninth efferent
artery (e.d7. 9) pours its blood into the eighth. From the junction of
the third and fourth and of the fifth and sixth arteries, short anastomotic
branches go off to the hypobranchial artery (§ 139).
157. The dorsal aorta (Figs. 20 and 21, @ao), passing
along the ventral face of the vertebral column: it gives off,
just before being joined by the third pair of efferent branchial
trunks, a large vessel from each side, which passes directly
outwards to the pectoral fin: this is the brachial or sub-
clavian artery (Fig, 20, s.c, Fig. 21, 67a). The aorta
then passes backwards in close contact with the verte-
bral column to the posterior extremity of the abdominal
cavity, giving off at about the level of the shoulder
girdle two large vessels, the coeliac (Fig. 20, cw), and
superior mesenteric (s.m) arteries (§§ 100 and 107),
then the arteries to the oviducts (ed) or epididymes, sper-
matic arteries (sf) to the testes or ovaries, a single
inferior mesenteric artery (¢.m), (§ 101), the numer-
ous small renal arteries (7) to the kidneys, and vessels to
the pelvic fins and the parietes of the body. At the end of
the abdominal cavity the dorsal aorta becomes the caudal
artery (c), which passes through the heemal arches of the
caudal vertebree (Fig. 10, 2@) to the end of the tail.
158. The caudal vein (Fig. 17, ¢), running parallel and ventral
to the caudal artery : on leaving the hzemal canal it divides into the two
renal portal veins (72), which pass to and ramify in the corre-
sponding kidneys (7f”) receiving numerous veins (77’) from the pelvic
and lumbar regions.
F 2
68 ZOOTOMY.
159. The femoral veins (Fig. 17, fm) bringing the blood from
pelvic fins : each divides into two trunks: one, the ilio-haemorrhoidal
vein (¢/.2), passes at first backwards and inwards, then forwards
along the lateral surface of the rectum and cloaca, and opening finally
into a posterior prolongation of the cardinal sinus : the second of the
two veins into which the femoral divides is the epigastric vein
(epg) ; it passes almost directly forward along the lateral wall of the
abdominal cavity, receiving veins from the abdominal walls (24), and
finally unites with the brachial vein (47).
It will be seen from Fig. 17, that the brachial, epigastric and ilio-
hzemorrhoidal veins really form one continuous trunk, opening anteriorly
into the precaval, posteriorly into the cardinal sinus, and receiving veins
from the pectoral and pelvic fins, the abdominal walls, and the rectum
and cloaca. The anterior portion of the epigastric should probably be
considered as representing the mammary vein of mammals, the two
being continuous instead of merely anastomosing.
160. The common carotid artery (Fig. 20, ¢.c), a small vessel
springing from the efferent branchial vessel of the hyoid arch: it first
passes somewhat inwards, and then directly forwards near the outer
edge of the base of the skull, sending a branch inwards—the internal
carotid artery (¢.c)—which unites with its fellow of the opposite side
to form an azygos trunk which perforates the base of the skull and is
distributed to the brain, especially to the pituitary body and saccus
vasculosus (§§ 176 and 177): the external carotid (ec) then passes
forwards and slightly outwards, and sends branches to the jaws,
snout, &c.
161. The vertebral artery (Fig. 20, vv), a small trunk arising from
the first of the three efferent branchial trunks: it passes inwards and
slightly forwards, perforates the base of the anterior vertebral plate
(§ 3), and is distributed to the brain and spinal cord, on the ventral
surface of which it forms, with its fellow, a plexus.
162, A small hyoidean artery (Fig. 20, Ay) given off from the
first efferent branchial: it passes to the dorsal side of the hyomandi-
bular and sends a branch to the pseudobranchia.
XXXIX. Remove two of the gills and make out, in
one by dissection, in the other by transverse
sections
163. -The cartilaginous branchial arch which supports
the inner edge of the gill.
THE SKATE. 69
164. The fibrous partition continued from the outer face.
of the branchial arch, and supported by the cartilaginous
branchial rays.
165. The soft vascular branchial filaments covering ,
both sides of the partition, to which they are firmly connected
along almost their whole length, their outer extremities only
being free.
166. The afferent branchial artery, running along the outer face of
the branchial arch, in the middle line: it is of considerable size at the
ventral end of the gill, but gradually diminishes towards its dorsal
end.
167. The efferent branchial arteries, two trunks smaller than the
afferent vessel, and running along the lateral edges of the arch, at the
bases of the rows of filaments. They are of considerable size at the
dorsal end of the arch, and diminish somewhat towards its ventral
end.
168. The thymus glands are exposed by the removal of the gills :
each is a whitish body, about an inch long, lying immediately dorsal
to the pharyngo-branchials,
C.—SPECIAL DISSECTION OF THE NERVOUS
SYSTEM AND SENSE ORGANS.
XL. It is advisable to take a fresh skate for the nervous
system, at least unless the subject used for the
foregoing work has been well preserved in strong
spirit. The viscera, with the exception of the
kidneys and vasa deferentia, may be removed at
once.
Expose the brain and anterior part of the spinal cord,
as directed in § XV., p. 46. Ifa preserved brain is
not available, the verification of the description of
the ventral surface must be left until the origins of
the nerves have been made out (§§ 179—189) when
the brain may be removed. Observe the following :—
70 ZOOTOMY.
169. The spinal cord (Fig. 22, my) lying in the neural
canal of the vertebral column, and, at the junction of the
latter with the skull, passing insensibly into the brain. It is
divided into a pair of dorsal and a pair of ventral
columns by deep dorsal and ventral fissures, and
is traversed through its centre by the minute central
canal.
170. The medulla oblongata or myelencephalon
(Figs. 22—25, m.o), the hindmost division of the brain :
passing forwards from its junction with the spinal cord, it
undergoes a gradual increase in diameter, and is produced
dorsally, on each side, into a greatly convoluted body, the
corpus restiforme (Fig. 22, a7). Both dorsal and
ventral surfaces of the medulla are marked with obscure
inedian grooves, continuous respectively with the dorsal and
ventral fissures of the spinal cord : the dorsal groove separates
the dorsal pyramids, the ventral groove the ventral
pyramids of the medulla.
171. The cerebellum (Figs. 22, 24, 25, cb), a median
structure, situated to the dorsal side of the myelencephalon,
and composed of two distinct lobes, a posterior, having the
form of an isosceles triangle with the apex directed back-
wards, situated between the restiform bodies, and a squarish
anterior, partly overlapping the optic lobes (§ 173). Both
lobes are marked on the surface by ridges (gyri) with inter-
vening depressions (sulci).
172. A small transparent area behind the cerebellum
(Fig. 22, 7 4), roofing over the fourth ventricle (§ 180).
173. The mesencephalon (Figs. 22—25, 0./, ¢.¢) con-
sisting on the upper surface of the two optic lobes
(0.2), ovoidal bodies, lying just in front of, and partly
overlapped by the cerebellum. The under surface of the
mesencephalon is formed by the crura cerebri (c.),
THE SKATE, 71
Fic, 22.—Raja nasuta. Dorsal view of the brain and anterior part
of the spinal cord, with the cerebral and anterior spinal nerves (half nat.
size).
On the left side the 2nd, 5th, and 7th—1oth cerebral nerves are
removed, and on the right side the 3rd, 4th, and 6th. The spinal
nerves are shown only on the left side: the distal end of the left
olfactory lobe is not shown.
Central Nervous System. my, spinal cord: mm.o, medulla
oblongata: vw. 4, fourth ventricle: ¢.7, corpora restiformia: cd, cere-
bellum: 0.4, optic lobes: ¢h, thalamencephalon : ¢.4, prosencephalon :
olf; olfactory lobes.
Nerves. /, olfactory: Z/, optic: /7Z, oculomotor: 2.7, branch of
oculomotor to internal rectus: s.7, to superior rectus: 7¢.7, to in-
ferior rectus: 7.0, to inferior oblique: /V, patheticus: V7, dorsal,
72 ZOOTOMY.
and /'>, ventral ramus of V7? orbito-nasal nerve: V2, palato-nasal
nerve: >, maxillary nerve: 773, mandibular nerve: V//?, palatine
branch of portio dura: V/ZZ>, hyomandibular branch: ¢.ty, chorda
tympani: VZ//, auditory nerve: ZX, glossopharyngeal nerve : X, vagus:
Ay, branch of glossopharyngeal to hyoid arch: 67. 1, branches of
glossopharyngeal and vagus to Ist branchial arch: 67. 2, dr. 3, 47. 4,
branches of vagus to 2nd, 3rd, and 4th branchial arches: v, ventral
(gastric and cardiac) branch of vagus: /, lateral branch of vagus: 67,
brachial plexus,
forward continuations of the ventral pyramids of the
medulla oblongata.
174. The thalamencephalon (Figs. 22, 24, 25, ¢h), a
small division of the brain just anterior to the optic lobes:
it consists of two lateral masses of nervous matter, the
thalami optici, between which is a space, covered only
by pia mater, the thalamoccele or third ventricle (v. 3).
175. The lobi inferiores (Figs. 23—25, 22) paired
ovoidal bodies on the under surface of the thalamencephalon.
176. The pituitary body or hypophysis cerebri
(Figs. 23—25, f/), a rounded structure on the ventral
surface of the brain, behind the lobi inferiores and attached
to a backward prolongation of the thalamencephalon called
the infundibulum; with it is connected anteriorly the
median artery formed by the union of the two internal
carotids (§ 160).
177. The saccus vasculosus (Figs. 23—25, 5.7, 5.0’).
a thin-walled hollow body, consisting of three lobes, two
large and paired, situated one on either side between the
pituitary body and the lobi inferiores, and a median azygos
lobe lying in the groove between the lobi inferiores.
173. The prosencephalon (Figs. 22—25, , dorsal or
posterior root of the same: J’//, VZ’, roots of the portio dura: V/ZJ/,
root of the auditory nerve.
bodies. Each bundle is seen to consist of an anterior
smaller and a posterior larger fasciculus. The former (Figs.
23, 26, and 27 V’*) goes to form the inferior ramus of the
Fic, 27.—Raja nasuta. The principal branches of the 5th, 7th, and
8th cerebral nerves (nat. size).
Va, ventral and ”», dorsal root of the fifth: 17, dorsal, and V™,
ventral ramus of the orbito-nasal nerve: V8, palato-nasal nerve : Be,
maxillary nerve: 173, mandibular nerve: pi.gu, nerve to upper jaw :
ya, nerves to the region of the nostrils: V2/, portio dura: VIZ,
auditory nerve.
first division of the fifth nerve, and the main part of its
third division, besides contributing fibres to the second
76 ZOOTOMY.
division: the latter (V°, V7Z, V7/Z) contains the remainder
of the fifth, the seventh, and the eighth nerves.
The fifth, seventh, and eighth nerves arise altogether by seven roots.
Two of these, a smaller dorsal (Fig. 26, Y’) and a larger ventral (V)
go to form the anterior fasciculus already mentioned, both arising ventro-
laterally from the medulla, The five roots forming the posterior fasci-
culus divide naturally into an anterior and 2 posterior set. The anterior
set consists of two roots, a dorsal (VZ/) and a ventral (7 7/’), together
forming the seventh nerve: the posterior set consists of three roots, a
dorsal (V'»), arising along with the dorsal root of the seventh, and two
ventral, arising close together: the uppermost ventral root unites
immediately with the dorsal root to form the remainder of the fifth
nerve (>): the lowermost ventral root (VZ/Z) constitutes the eighth
nerve.
187. The sixth pair (abducentes, Figs. 22 and 23, V7)
arise from the under surface of the medulla oblongata,
internal to the eighth. They are very fine nerves, and are
easily detached with the pia mater.
188. The ninth pair (glossopharyngei, Figs. 22, 23,
25, JX), a small pair arising from the sides of the medulla
oblongata, and passing outwards and forwards to enter the au-
ditory capsule at about the centre of its inner surface (§ 33),
189. The tenth pair (vagi or pneumogastrici, Figs. 22,
23, 25, X ), arise by several roots from the lateral regions
of the hinder part of the medulla oblongata, and pass out-
wards and backwards to leave the cranial cavity by a foramen
in the posterior part of the inner surface of the auditory
capsule (§ 33).
XLI. Remove the skin from the dorsal surface of the
head, on both sides of the cranial cavity, and by
carefully dissecting away the connective tissue
from the eye and surrounding parts, make out
190. The dorsal ramus of the orbito-nasal nerve (first
division of the fifth, Figs. 22 and 27, V%*) lying close
THE SKATE, 77
against the outer side of the skull wall, and springing from
the posterior dorsal root mentioned in § 186,
191. The superior oblique muscle of the eye, passing
from its origin at the anterior part of the skull wall to its
insertion in the antero-superior region of the eye-ball.
192. The superior rectus muscle, arising from the
skull wall, a little in front of the auditory capsule, and
passing to its insertion on the postero-superior region of the
eye-ball.
193. The internal rectus, arising immediately in front
of the superior rectus and passing to the front part of the
eye-ball, beneath the superior oblique.
194. The external rectus, arising just behind the
superior rectus and passing almost directly outwards to the
posterior region of the eye-ball.
195. The fourth nerve (Fig. 22, ZV), leaving the skull
by its numerous foramina, and spreading out in a fan-like
manner on the dorsal surface of the superior oblique
muscle.
196. The third nerve (Fig. 22, 77/7), which, after leav-
ing the skull, sends branches to the superior (s.7) and
internal (7) recti, and then curves round the posterior
edge of the former: its further course will be seen at a
later stage (§ 203).
197. The sixth nerve (Fig. 22, V7), leaving the skull
along with the fifth and seventh, and being distributed to
the external rectus muscle.
XLII. Remove the superior oblique and the superior
and external recti. Make out
198. The ventral ramus of the orbito-nasal nerve
(Figs. 22 and 27, V?") springing from the anterior fasciculus
mentioned in § 186: after leaving the skull by the trigeminal
foramen, it passes over the external rectus, under the
78 ZOOTOMY.
superior and internal recti, over the peduncle of the eye
(§ 200) and the optic nerve (§ 199), under the superior
oblique, and finally unites with the dorsal ramus as it
perforates the nasal capsule (§ 205).
199. The optic nerve (Fig. 22, 77), which, after leaving
the skull, passes almost directly outwards to the hinder
region of the eye-ball. Its extra-cranial portion is invested
with a strongly pigmented sheath.
200. The ophthalmic peduncle, an irregular stalk of
cartilage, articulated at its proximal end with the skull wall
behind the optic foramen, and at its distal end with a knob
on the sclerotic coat of the eye.
201. The inferior oblique muscle of the eye, running
parallel with the superior oblique, to the antero-inferior
region of the eye.
202. The inferior rectus, arising with the other recti,
and passing parallel with the superior rectus to its insertion
on the inferior region of the sclerotic.
203. The remaining course of the third nerve (Fig. 22,
Z/1): after curving round the superior rectus, it passes
forwards and sends branches to the inferior rectus (¢#.7) and
inferior oblique (2.0).
XLIII. Remove successive slices from the nasal cap-
sule, until the following structures are brought into
view.
204. The strongly pigmented nasal sac, filling up the
cavity of the nasal capsule.
205. The orbitc-nasal nerve (Fig. 22, ¥1) which, just
before the junction of its two rami, enters the nasal capsule,
and divides into two branches, a large one which passes
along the outer edge of the rostrum, and a small one,
which passes outwards and forwards over the roof of the
nasal sac.
THE SKATE. 79
206. The distal ends of the olfactory lobes (Fig. 22, olf),
each forming a slightly convex white band on the dorsal
surface of the corresponding nasal sac.
XLIV. Remove one of the nasal sacs, and note
207. Its cup-like form, the cavity being open below.
208. The ridges into which its lining of mucous mem-
brane is raised: they are arranged in two rows at night
angles to a central ridge.
XLV. Remove the eye with its remaining muscles, and
set it aside for future examination.' Dissect out
209. The second division of the fifth nerve (Figs. 22 and 27,
V?), arising mainly from the posterior fasciculus mentioned
in § 186, but also receiving fibres from the anterior fascicu-
lus: it passes forwards and slightly outwards, and divides
into two chief branches, an internal, the palato-nasal
nerve (/7*) and an external, the maxillary nerve (V»)
the former passing directly forwards alongside the cranial
wall and beneath the eye muscles, and the latter passing
outwards and forwards towards the antorbital cartilage
($ 35).
210. The third division of the fifth, or mandibular
nerve (/73), arising mainly from the anterior, but receiving
fibres from the posterior fasciculus: it runs parallel with the
common trunk of the second division as far as the bifurcation
of the latter, and then takes a course internal to and nearly
parallel with the maxillary nerve.
The three divisions of the fifth nerve supply between them all the
anterior part of the head: the orbito-nasal goes to the dorsal region of
the rostrum and nasal capsule, and to the gelatinous tissue in their
neighbourhood : the palato-nasal to the ventral region of the same parts,
as well as to the fronto-nasal process and the movie? it also sends
1 The eye must be dissected in the fresh condition : for directions see _
§ LIL, p. 84.
80 ZOOTOMY,
fibres to the upper jaw: the main part of the mandibular nerve goes to
the sensory tubes in front of the antorbital cartilage: the mandibular
goes to the lower jaw (outer side), but also sends a large branch to the
upper jaw. There is, however, endless variation in the distribution of
these nerves.
XLVI. Carefully slice away the cartilage forming the
roof of the auditory capsule, taking care not to
injure the membranous labyrinth (§ 213); dissect
away the connective tissue, &c., from the hyo-
mandibular, and the muscles on the floor of the
orbit, making out
211. The hyomandibular nerve, or posterior branch
of the seventh (Fig. 22, /’//*): after leaving the cranial
cavity it curves round the anterior border of the auditory
capsule, and passes almost directly outwards, over the
hyomandibular cartilage and behind the jaw muscles, break-
ing up at last into a number of fibres which are distributed
to the large sensory tubes situated in front of the gills. As
the hyomandibular nerve passes the jaw muscles, it gives off
two small branches (¢¢y), which represent the chorda
tympani of the higher animals, and are distributed to the
inner surface of the lower jaw.
212, The palatine nerve (Fig. 22, VZ/*), or anterior
division of the seventh, which separates from the common
root of the seventh soon after its exit from the skull, passes
in front of the spiracle, and breaks up into a number of
branches, some of which are distributed to the mucous
membrane of the mouth and others to the pseudobranchia.
213. The membranous labyrinth (Fig, 28) or
internal ear, a delicate apparatus enclosed within the auditory
capsule, and consisting of a large sac or vestibule (2),
and three semicircular canals, one of which is anterior
and vertical (a.s.c), another posterior and vertical (#.s.¢), and
the third horizontal (A.5.c).
THE SKATE. 81
The vestibule is a rounded sac with two small diverticula, containing
an otolithic mass which consists of minute calcareous particles bound
together by gelatinous connective tissue: from its dorsal surface pro-
ceeds a canal, the aqueductus vestibuli (¢7./), which passes through
the roof of the auditory capsule, and dilates between the latter and the
external integument into a small sac, lined with strongly pigmented
epithelium ; this opens on the surface of the head bya minute aperture.
The canals form nearly complete circles, the posterior being the largest of
the three. Each is dilated at one part of its course into an ampulla (a).
The posterior canal communicates with the vestibule in an unusual
manner, namely by a short distinct tube (x).
Fic, 28.—Raja batis. The right membranous labyrinth, seen from
the outer side (nat. size).
v, vestibule: ag.f, aqueductus vestibuli: @.s.c, anterior, f.s.¢,
posterior, and 4.s.c, horizontal semicircular canals: @,a,a, ampulle :
x, side tubulure by which the posterior canal communicates with the
vestibule : 2,#,2, branches of auditory nerve.
XLVII. Clear away the skin and muscles from the
dorsal surface of the anterior vertebral plate and
from that of the gills. Dissect out
214. The vagus or tenth nerve (Fig. 22, X ), which, after
leaving the skull by the vagus foramen, passes directly back-
wards between the inner boundaries of the gills and the
lateral ridge of the anterior vertebral plate, giving off the
branchial nerves as it goes, to the front edge of the pro-
pterygium, where it divides into two chief branches, a ventral
branch (X,z), to the stomach and heart, and a lateral branch
(X,J), which passes between the peritoneum and dorsal
G
82 ZOOTOMY.
muscles, on the dorsal side of the spinal nerves (§ 222).
The branchial nerves (dr. 2—5) are four in number, and
are given off opposite the four posterior gill clefts. Each
one, soon after leaving the vagus divides into two branches,
one of which goes to the posterior face of the gill in front of
the cleft to which it belongs, the other to the anterior face of
the gill next behind. In this way all the gill filaments
except those on the posterior face of the hyoid and those on
the anterior face of the first branchial arch (first and second
demibranchs) are supplied.
21s. The glossopharyngeal or ninth nerve (Fig. 22,
7X), seen emerging from its foramen, in front of the anterior
branchial branch of the vagus: it divides above the first gill
cleft and supplies the hyoid half-gill and the anterior half-
gill of the first branchial arch (Ay, 47.1).
216, The brachial plexus (Fig. 22, 47), lying in the
depression between the median and lateral ridges of the
anterior vertebral plate, and formed by the convergence and
subsequent union of the first sixteen or eighteen spinal
nerves: the common trunk thus formed turns round the
posterior edge of the lateral ridge, and passes outwards
behind the propterygium to the pectoral fin. Each spinal
nerve arises by two roots, a dorsal (Fig. 11, d.7) and a
ventral (v.v), the former having a ganglionic enlargement :
the two pass separately through the wall of the neural canal
(see §§ 8, 10) and unite outside it in the trunk (¢7) of the
nerve.
XLVIII. Remove carefully the greater part of the
membranous labyrinth, cut away the walls of the
auditory capsule, and make out
217. The auditory or eighth nerve (Fig. 22, VZ/7),
entering the capsule at its anterior end through the in-
ternal auditory meatus, and passing backwards, sends off
THE SKATE. 83
branches to the vestibule and ampullz of the semicircular
canals (Fig. 28, 7).
218. The course of the ninth nerve through the capsule
(Fig. 22, JX): it enters the latter by an aperture in about
the middle of its anterior wall, passes backwards and out-
wards nearly parallel with the eighth and leaves the capsule
in its postero-external region by an aperture already noticed
in the skull (§ 25).
219. The course of the vagus through the auditory
capsule (Fig. 22, X): leaving the cranial cavity it passes
through a canal excavated in the postero-internal wall of the
capsule, the outer end of the canal being the vagus foramen
(see §§ 24, 33).
XLIX. Place the fish in the supine position, find the large
sympathetic ganglion mentioned in § 150, and trace back
220. The sympathetic nerve, which consists of a longitudinal cord
on each side of the vertebral column, presenting ganglia at intervals,
and connected by rami communicantes to the spinal nerves. As
already mentioned, the adrenals or supra-renal bodies are in intimate
connection with the sympathetic ganglia,
L. Dissect away the kidneys and the peritoneum
from the dorsal wall of the abdominal cavity,
and note
221, The spinal nerves, passing to the body walls and
fins: many of them converge, and exhibit a tendency to the
formation of plexuses.
222. The lateral branch of the pneumogastric (Fig. 22,
X,/), a longitudinal nerve, lying to the dorsal side of the
spinal nerves.
LI. Make a longitudinal vertical section of a brain
hardened in spirit, and note
223. The relations of the various divisions of the brain
already seen, and of the cavities they contain (Fig. 24): the
G2
84 ZOOTOMY.
latter are seen to form a continuous series, from the
myeloccele (v. 4), which is continued behind into the central
canal of the spinal cord, through the mesoccele (ag.s) to the
thalamoccele (v. 3). The latter is further seen to send a
small prolongation forwards into the otherwise solid pros-
encephalon, and another downwards and backwards into the
infundibulum.
LII. Make out the chief structures in the eye, first
viewing from the outside,then removing successively
the sclerotic (§ 224), choroid (§ 225) and retina
(§ 227) from the flattened dorsal surface.
224. The cartilaginous sclerotic or outer covering of the
eye-ball: externally it passes into the transparent fibrous
cornea, which is the part exposed to view in the entire
animal; internally, the sclerotic is pierced by a small aperture
for the passage of the optic nerve, and is raised into a knob-
like prominence for articulation with the ophthalmic
peduncle (§ 200).
22s. The black choroid lining the sclerotic: at the
junction of the latter with the cornea, it passes into the iris,
the coloured (yellow and black) part of the eye, seen from
the outside through the transparent cornea. The iris is
pierced by a central aperture, the pupil, the upper margin
of which is produced into a sort of curtain, divided at
its free edge into several processes. Between the iris
and the cornea is a space, the anterior chamber
of the eye, filled with a watery fluid, the aqueous
humour.
226. The crystalline lens, a nearly globular transparent
body, situated immediately behind the iris.
227. The retina, a delicate, greyish-white membrane,
lying immediately within the choroid, from which it is
readily detached except at the place of entrance of the optic
THE SKATE. 85
nerve. Externally (ze towards the cornea) it ends at the
junction of the choroid and iris.
228, The vitreous humour, a gelatinous substance, fill»
ing the whole posterior chamber of the eye, or space
enclosed between the retina and the inner surface of the
lens and iris.
THE COD.
Tue CoprisH (Gadus morrhua).
Tue WHITING (G. merlangus).
THE Happock (G. aglefinus).'
A.—THE SKELETON.
I. A cod’s skeleton is readily prepared by placing the
fish, after removal of the viscera, into boiling
water for a few minutes, and thus stripping off
the flesh and other soft parts. By this process the
bones are obtained separate from one another,
with the exception of those forming the brain-case,
the high temperature causing gelatinization of the
connective tissue which unites them. The bones
should be removed one by one and placed out in
order, to dry, each being as far as possible identi-
fied and its relations to surrounding bones deter-
mined before removal. As this is a matter of
considerable difficulty in the case of the bones of
the head, it is advisable to prepare a second skull
1 These are the three commonest species of the genus Gadus brought
to the English markets : the differences between them are comparatively
unimportant (see §§ 8, 18, 19, 72, 80, 85).
THE COD. 87
by carefully dissecting away the muscles, &c.,
while fresh, without either boiling or maceration,
the bones being kept together in their natural
position by their ligaments. Of this skull it is as
well to make a longitudinal vertical section by
sawing through the brain-case a little to one side
of the middle line and cutting through the mandi-
bular and hyoidean symphyses (§§ 51 and 52) : from
the worst side, the jaw apparatus should be removed
from the brain-case by disarticulating the palatine
(§ 46, Fig. 29, 2) and the hyomandibular (§ 40,
Fig. 29, 4m). In the first skull the bones of the
brain-case may be separated from one another by
boiling for a considerable time and then gently
pulling them asunder.
It is advisable to examine the second or entire skull
before drying, so as to see its cartilaginous
portions (§§ 47, 49, &c.).1
II. In the skeleton as a whole note the following
regions :—
1. The vertebral column, consisting of (a) trunk
vertebra, bearing movable ribs which do not unite
1 Owing to the small amount of cartilage left in the adult cod’s skull,
the beginner will find some difficulty in seeing the relation between it
and that of the skate. A useful intermediate type is furnished by the
salmon or trout, in which there is a cartilaginous brain-case, quite
readily comparable with that of the skate but containing the occipital
and otic bones, basi- and pre-sphenoid, as endogenous ossifications : the
remaining homologues of the bones of the cod’s brain-case (parietals,
frontals, parasphenoid, vomer, &c.) are seen to be membrane-bones,
easily detachable without injury to the cartilage (see Parker and
Bettany, Morphology of the Skull, p. 66). The skull of the salmon
or trout should be prepared like that of the cod, by b iling ; the brain-
case, Meckel’s cartilages, &c., may be preserved by the glycerine jelly
process, described on p. 2.
88 ZOOTOMY.
below, and (4) caudal vertebree, with complete inferior
arches.
2. The skull, consisting of (2) the brain-case, formed
of a number of bones firmly united by suture; (2) a num-
ber of more or less loosely attached bones, in relation
with the brain-case, and constituting the skeleton of the
upper and lower jaws and suspensorium, the hyoidean ap-
paratus or tongue-bones, and the gill-covers; and (¢) the
branchial arches or bony framework which supports
the gills,
3. The bones of the median fins, namely, the three
dorsal fins, the two anal fins, and the caudal fin
(see § 94).
4. The bones of the pectoral fins, or fore-limbs, and
of the shoulder girdle to which they are attached
($ 95).
5. The bones of the pelvic fins, or hind-limbs, and
of the hip-girdle to which they are attached (§ 96).
III. Examine a vertebra from about the middle of the
trunk region, and make out
6. The centrum or body of the vertebra, a short bony
cylinder with deeply concave anterior and posterior ends ;
the bi-convex spaces between adjacent centra are filled in the
recent state by a gelatinous substance, the remains of the
embryonic notochord.
7. The neural processes, two plates arising vertically
one from each side of the upper surface of the centrum,
near its anterior end, and uniting with one another to form
the neural arch, from the vertex of which the long slender
neural spine springs and takes a direction upwards and
slightly backwards. From the anterior edge of each neural
process a somewhat triangular projection is continued
forwards, and answers to the anterior zygapophysis of
THE COD. 89
the higher vertebrata: there is no true posterior zygapophy-
sis, but from the hinder end of the centrum arises on each
side a small vertical process, which fits owés¢de the anterior
zygapophysis of the vertebra next behind.
8. The transverse processes, large outstanding
plates of bone, which spring one from each side of the
centrum, and pass outwards, downwards, and backwards.
The transverse processes are proportionally much larger in the
Haddock than in either of the other species.
IV. In the rest of the trunk region, the following are
the chief points to be verified :—
g. In the first vertebra or atlas the centrum is very
short from before backwards, the neural spine is vertical,
the transverse processes are absent, and the anterior zyga-
pophyses are very large and come into relation with the
posterior part of the skull (exoccipital bone, § 22); im-
mediately beneath each zygapophysis is a small articular
facet for articulation with a corresponding facet on the
exoccipital. The union between the skull and the atlas is
thus much more intimate than that between any two
vertebree, and in consequence the atlas is, in preparation,
often left attached to the skull.
10. In the next three or four vertebre a gradual transition
is seen between the characters of the atlas and those of
the typical trunk vertebra described in §§ 6—8.
11. The transverse processes in the anterior part of the
trunk region look almost directly outwards; proceeding
towards the caudal region, they gradually increase in size
and come to look more and more downwards and back- :
wards, until in the last trunk vertebra they nearly meet.
12, Between the ventral or proximal ends of contiguous:
neural arches, spaces are left : these are the intervertebral |
go ZOOTOMY.
foramina ; they serve for the transmission of the spinal
nerves.
13. The ribs, slender, flattened bones, articulated to the
distal ends of the transverse processes and curving outwards
and downwards.
14. The inter-muscular bones, shorter and slenderer
than the ribs, but otherwise resembling them : they are articu-
lated one to each transverse process on its dorsal side
and a short distance from its distal end, and curve upwards
and outwards.
V. In the caudal vertebree note
15. The hemal arch, formed by the union in the
middle ventral line of two heemal processes, springing one
from each side of the ventral surface of the centrum near
its anterior end ; from the point of union a hemal spine is
given off and passes downwards and backwards. The
heemal processes give rise to anterior zygapophyses like those
on the neural arches, and similarly articulating with small
processes from the centrum of the vertebra next in front.
16. In the anterior caudal region the hzemal are very much
larger than the neural arches, but passing back the former
diminish progressively until there is no difference of import-
ance, either in the size of the arches or the length of
the spines, between the neural and heemal aspects of the
vertebrze.
17. Following the last undoubted caudal vertebra is the
small fan-shaped hypural bone, which together with the
somewhat flattened posterior neural and haemal spines
supports the tail-fin.
VI. In the median fins make out
18. The interspinous bones of the dorsal and anal
fins, alternating with the neural and hemal spines respec-
tively, and attached to them by fibrous tissue.
THE COD. g1
In the Whiting the anterior anal fin extends in front of the caudal
region, so that most of its interspinous bones are unconnected with the
vertebrze and lie free amongst the muscles,
19. The fin-rays, attached, in the case of the dorsal and
anal fins, at their proximal ends to the interspinous bones,
and forming the actual skeleton of the fins; each is a deli-
cate, rod-like bone, transversely jointed and flexible at its
distal end (“soft fin-rays’’). In the caudal fin the fin-rays
come into direct relation with the hypural bone and the
posterior neural and hemal spines.
In the Codfish there are 13 rays to the first dorsal fin, 16 to 19 to
the second, 17—19 to the third, 18—19 to the first anal, and 17—18 to
thesecond, The formula for the fin rays is therefore, D. 13 | 16—19 |
17—19. ) goes directly forwards,
parallel with and close to the parasphenoid : the third division (mandi-
bular, V3), passes forwards, downwards, and outwards to the lower jaw,
upon reaching which it divides into two chief branches, one passing
above, the other below Meckel’s cartilage. The cutaneus quinti (V°)
arises from the main trunk, The seventh nerve takes a direction out-
wards, downwards, and backwards, and soon divides into two branches
which pass through the two foramina in the hyomandibular (§ 40) : the
anterior of these divisions soon divides again, the hindermost branch
going to the operculum, the other (chorda tympani) to the lower jaw :
the posterior division takes a curve inwards, backwards, and down-
wards, reaches the inner side of the epihyal, and passes along the inner
face of the hyoidean arch,
194. The sixth pair of nerves (abducent, VI), each
arising by two delicate roots from the ventral surface of
the medulla oblongata.
195. The eighth pair of nerves (auditory, VIII), each
arising by three large roots from the lateral surface of
the medulla ; these pass directly outwards to the auditory
organ.
196.. The ninth (glossopharyngeal, IX) and tenth
(vagus or pneumogastric, X) nerves, arising together
from the lateral surface of the medulla; the vagus arises by
two large roots which pass outwards and backwards and
join one another just before leaving the cranial cavity; the
glossopharyngeal arises by one main root, a little posterior
to the anterior root of the tenth, to the ventral side of
which it passes to make its exit from the skull.
On leaving the skull, the glossopharyngeal divides into two branches,
the anterior and smaller of which goes to the pseudobranchia, the
posterior to the anterior face of the first branchial arch.
The vagus, on leaving the skull, sends off branchial nerves which
supply the branchial arches in the same manner as in the skate (p. 81,
§ 214),.it then divides into two trunks, one passing ventralwards and
128 ZOOTOMY.
supplying the heart and stomach, the other becoming the lateral or
cutaneous nerve, the distribution of which has been already seen (§ 99).
The anterior root of the vagus gives off a small nerve which joins the
cutaneus quinti (X°).
XXXVII. Lift up the cerebellum and cut it away close
to its attachment ; note
197. The dorsal surface of the medulla oblongata, and
the cavity (fourth ventricle, v. 4) inclosed between it and
the cerebellum.
198. The lobi posteriores (79), a pair of rounded
elevations on the anterior part of the floor of the fourth
ventricle, and between them a large transverse comunissure
(cm') passing from one side of the medulla to the other,
and in a dorsal view giving the fourth ventricle the appear-
ance of two distinct cavities ; that these are continuous may
be seen by passing a guarded bristle beneath the commissure.
XXXVIII. Carefully lift up the posterior edges of the
opticlobes and remove enough of them to display
thoroughly the cavity thus laid bare: observe
199. The optic ventricles, large cavities in the optic
lobes, continuous with one another in the middle line so
as to form in reality a single cavity: the roof of this, just
removed, is very thin, its floor extremely thick.
200. The tori semicirculares (4s), two somewhat
kidney-shaped elevations, situated, one on each side on the
floor (crus cerebri) (cc) of the optic ventricle.
201. The fornix of Gottsche (£G), a somewhat shield-
shaped mass, situated between the tori semicirculares, and
formed as an infolding of the posterior wall of the optic
lobes.
202. A valve-like plate of nervous matter («), formed as
an infolding of the anterior wall of the optic lobes, and
overlapping the anterior end of the fornix of Gottsche.
THE COD. 129
203. The aqueduct of Sylvius (ag.s) a median pas-
sage continuous behind with the fourth ventricle and covered
by the fornix of Gottsche ; it is best made out by passing
a guarded bristle forwards from the fourth ventricle and
then removing the fornix of Gottsche ; it is in free com-
munication with the optic ventricle. The anterior end of
the aqueduct of Sylvius is all that represents the third
ventricle (v. 3).
XXXIX. Make a longitudinal vertical section of
another brain, and observe
204. The relations of the parts already seen, particularly
those of the fourth ventricle, aqueduct of Sylvius, and optic
ventricle. ;
205. The downward continuation of the rudimentary third
ventricle in front of the anterior truncated termination of the
crura cerebri ; in this way the infundibulum (77) is formed ;
it extends backwards and downwards between the lobi in-
teriores, and to its anterior and inferior wall the pituitary
body is attached.
THE LIZARD.!
Tue Green Lizarp (Lacerta viridis),
Tue Sanp Lizarp (ZL. agilis).
THE ScaLy Lizarp (Zootoca vivipara).
(A).—THE SKELETON.
I. The skeleton of the lizard may be prepared either
by maceration, z.e. by allowing the roughly cleaned
bones to soak in water until the remaining tissues
are decayed, or by plunging for a few seconds
into boiling water: in either case, the muscle,
connective tissue, &c., still adhering, is afterwards
dissected off until the bones are clean. It is
advantageous to have two skeletons: in one the
bones, with the exception of the skull, are not
separated from one another, and the whole
skeleton is set out and dried in the natural posi-
tion: the skull should be removable, and it is as
1 The following description applies strictly to the Green Lizard,
which although not an actual British species, is very common in Jersey ;
it is larger than the indigenous forms, and is readily obtained of the
dealers in natural history objects. The distinguishing characters of the
three lizards will be found on p. 156, § 124.
THE LIZARD, 13
well to make a longitudinal vertical section of it
with a fret-saw. In the other skeleton the bones
should be disarticulated, the vertebree being strung
on a string or wire, as separated, so as not to
disturb their order, and the other bones placed
out in proper position on a card: the skull
should be boiled for + to $ an hour, and its con-
stituent bones gently pulled apart. This second
skeleton will of course bear more prolonged macera-
tion or boiling than the first or “‘ natural” skeleton.
In both cases the hyoidean apparatus (§ 79-83
Figs. 39-40), must be dissected out with great care,
as it partly consists of delicate cartilages: con-
siderable care is also required in cleaning the
sternal ribs (§ 23). For the study of the chondro.
cranium a specially prepared skull is necessary :
(see § VI. p. 143.)
II. Observe the general composition of the skeleton
as follows:
1. The vertebral column, consisting of numerous
separate vertebrz, divisible into (2) a cervical region
of eight vertebr, forming the skeleton of the neck; (4) a
thoracico-lumbar region of twenty-two vertebre, forming,
with the ribs and sternum, the skeleton of the trunk: (¢)a
sacral region of two vertebre, giving attachment to the
pelvis: and (d@) a caudal region, consisting of a variable
number of vertebre supporting the tail.
2. The skull, articulated to the first cervical vertebra,
and consisting of (a2) the brain-case and upper-jaw:
(2) lower-jaw, composed of two separate rami : and (¢)
the hyoidean apparatus supporting the tongue.
3. The ribs, springing in pairs from many of the vertebra :
they become marked in the posterior cervical region, attain
K 2
132 ZOOTOMY.
their maximum size in the anterior thoracic region, where
they are united to the sternum (§ 4), and undergo a gradual
reduction in size in the posterior thoracico-lumbar region.
4. The sternum and shoulder-girdle, together forming
an inverted arch of mingled bone and cartilage in the
anterior thoracic region, to the vertebree of which the sternum
is united by ribs.
5. The fore-limb, articulated to the shoulder-girdle,
6. The pelvis or hip-girdle, attached to the sacral
vertebre.
7. The hind-limbs, articulated to the pelvis.
III. Observe the following points in the vertebral
column :
8. The characters of one of the anterior thoracic vertebre :
it consists of a ventral cylindrical portion, the centrum,
concave in front, convex behind (proccelous), from which
rises up on each side a vertical plate, the neural process
or neurapophysis: this, uniting with its fellow in the
middle dorsal line, incloses the neural arch, which is
produced at its apex into a short, backwardly directed
neural spine.
9. The zygapophyses, horizontal processes, two anterior,
given off one from each side of the anterior border of the
neural arch, and two posterior, similarly related to its posterior
border: the anterior pair bear smooth articular facets on
their dorsal surfaces, the posterior pair on their ventral
surfaces.
10. The capitular facets, one on each side of the
vertebra, at the junction of the centrum and neural arch
and close to the anterior border of the latter : they serve for
the articulation of ribs,
11. The mode of articulation of successive vertebra :
each fits by the concave anterior face of its centrum against
THE LIZARD. 133
the convex posterior face of the centrum next in front,
while its anterior zygapophyses are overlapped by the pos-
terior zygapophyses of the preceding vertebra.
12. The intervertebral foramina, spaces between the
neural arches of successive vertebrae, due to the fact that
each neurapophysis is notched, slightly in front, more deeply
behind.
13. The cervical vertebre, with the exception of the
first two, resemble the thoracic in essential respects, but are
proportionally shorter from before backwards.
14. A sub-vertebral wedge-bone (autogenous hy-
papophysis) is developed in connection with the ventral
face of the centrum of the third cervical vertebra at its
anterior end: it forms a small downwardly directed process,
its anterior face furnishing part of the concave anterior
surface of the vertebra.
15. The second cervical vertebra or axis, distinguished
by the short conical odontoid process projecting forwards
from the anterior face of its centrum, and constituting
a separate ossification or os odontoideum. ‘The axis,
like the succeeding vertebra, has a sub-vertebral wedge-bone,
16. The atlas, or first cervical vertebra, a ring-like bone,
consisting of three separate ossifications, one ventral, re-
presenting part of the centrum, the others dorso-lateral,
representing separate neurapophyses: between the latter
stretches, in the fresh state, a transverse horizontal ligament,
the space above which represents the neural arch of the
atlas, while between it and the ventral ossification fits the
odontoid bone, representing the dorsal portion of the
centrum of the atlas. The anterior face of the atlas presents,
ventrally, a smooth articular facet for the occipital condyle
of the skull (§ 31).
17. The posterior thoracico-lumbar vertebre differ but
134 ZOOTOMY.
little from the anterior or true thoracic, save for the fact that
their centra are somewhat shorter.
18. The sacral vertebre, distinguished by their short
centra, and by the presence of large, expanded, outwardly
directed transverse processes, against which the ilia
(§ ror) abut: these processes are formed as distinct
ossifications, and represent sacral ribs. The curvature of
the posterior face of the centrum of the first, and of the
anterior face of the centrum of the second sacral vertebre,
is somewhat less marked than in the other vertebre: the
posterior convexity of the second sacral is more than usually
pronounced.
19. The anterior caudal vertebra resemble the sacral,
but have longer centra, slenderer transverse processes, and
longer neural spines.
20. The chevron bones, attached to the ventral faces
of the centra of many of the anterior caudal vertebrae: each
is Y-shaped, the paired upper limbs of the Y articulating
with facets immediately beneath the posterior convexity of
the centrum, while the stem or lower-limb is free and takes
a direction downwards and backwards.
21. The posterior caudal vertebra undergo a_ gradual
simplification of structure towards the distal end of the tail,
being finally reduced to small rod-like centra.
In all the caudal vertebree but a few of the antcrior ones, there is
a transverse vertical zone of the centrum which remains unossified, and
along which the vertebra readily separates: many lizards lose their
tails by the parting of the tissues across one of these weak places, and
a new tail is formed, the supporting axis of which is not divided into
vertebrx, but consists of an unjointed calcified rod.
IV. Make out the characters of the ribs and sternum
as follows :—
22. The sternum, (Fig. 39, p.157, sf), a rhomboidal plate
THE LIZARD. 135
of cartilage, with a small central fontanelle, and produced
posteriorly into two slender flattened cornua (s¢’): with the
antero-lateral edges of the sternum the shoulder-girdle
articulates (§ 84), to its postero-lateral edges and cornua the
sternal ribs are united (§ 23).
23. The five anterior thoracic ribs: each consists of a
dorsal bony portion (vertebral rib) articulated to the
corresponding vertebra by an undivided head, and of a
ventral cartilaginous portion (sternal rib) attached to the
sternum, The first three sternal ribs are united with the
postero-lateral edges of the sternum, the fourth and fifth
with its cornua (see Fig. 39).
24. The posterior thoracic ribs do not meet the sternum,
and undergo a gradual diminution in size from before back-
wards, the sternal rib being finally reduced to a small
‘cartilaginous tip to the vertebral rib (see Fig. 39).
25. The cervical ribs, occurring in connection with all
but the first three cervical vertebrae: those belonging to the
fourth and fifth vertebrze are short and flattened, the others
resemble the thoracic ribs, but do not reach the sternum.
V. In the skull, note—
26. Its general shape : it has a somewhat pyramidal form,
the base of the pyramid being represented by the hinder
surface, the apex by the anterior extremity.
27. Its dorsal surface is formed by a large number of
roofing bones, in which it is often difficult to distinguish
the sutures or lines of junction between the bones from
the depressions marking the insertions of the overlying
epidermic scales.
28. The roofing bones are continued over the lateral
surfaces of the skull, bounding the orbits or cavities for the
eyes, and joining with the bones which. constitute the
alveolar margin along which the teeth are ranged.
136 ZOOTOMY.
29. On either side of the anterior extremity of the skull is
an aperture, the anterior nasal fossa, in which, in the
undried skull, are seen the cartilages bounding the external
nares (§ 70, Fig. 37).
30. The foramen magnum (Fig. 37, fm), a median
rounded aperture on the hinder surface of the skull, leading
into the brain cavity.
31. The occipital condyle (Figs. 35 and 37, 0.0), a
rounded surface beneath the foramen magnum, articulating
with the atlas.
32. The posterior temporal foss@, two large vacuities,
one on either side of and above the foramen magnum: they
are bounded above and on the outside by the roofing bones,
and on the inner side by the bones which limit the foramen
magnum and form the actual roof of the brain cavity.
33. The parotic process (Fig. 37, p.0c), a horizontal
bar of bone, extending on each side directly outwards from
the side wall of the brain-case and bounding the posterior
temporal fossa below: the part of the wall of the brain-case
from which it springs lodges the organ of hearing, and is the
auditory capsule.
34. The posterior nasal fossz, small paired apertures
on the ventral surface of the snout, at about the level of the
front edge of the orbit.
35. The palatine foramen, a large oval aperture, on
each side, just behind the posterior nasal fossa, and internal
to the hindermost teeth. @
36. The inferior temporal fossa, a large vacuity,
separated by a bony bar (the transpalatine, § 61) from
the palatine foramen, and bounded externally by a number of
small scale-like bones which continue backwards the
alveolar margin.
37. The glenoid surface, for the articulation of the
THE LIZARD. 137
lower jaw ; a pulley-shaped surface, forming the hinder angle
of the inferior temporal fossa, and borne by a curved bone
the quadrate (§ 53).
38. The basis cranii, a broad plate forming the floor of
the brain-case, and continued forwards in the perfect skull
by the interorbital septum (Figs. 35 and 37, z0.s), a
plate of cartilage forming a median vertical partition between
the orbits (§ 69).
Fic, 35.—Lacerta agilis. Longitudinal vertical section of the
skull (after W.K. Parker, slightly altered) & 4. ‘he cartilaginous
parts are distinguished by dotting, the membranous spaces by cross-
hatching.
als, alisphenoid: 4.0, basioccipital: 4.f¢, Dasipterygoid : 6.5, basi-
sphenoid : ¢.0, exoccipital : ¢f.0, epiotic ; ¢.f¢, epipterygoid: fo, fon-
tanelle: /v. frontal: z.0.5., interorbital septum: x2, nasal: 0.c, occi-
pital condyle : of.0, opisthotic : pa, parietal : pa.s, parasphenoid : p.mzx,
premaxilla: pr.0, prootic: s.m#x, septo-maxillary: s.2, septum nasi;
5.0, supraoccipital : ve, vomer . I—XII, foramina for exit of the cere-
bral nerves.
39. The tympano-eustachian fossa, a depression just
external to the basis cranii and bounded by the quadrate :
against its dorsal wall lies a small rod of bone, the
columella auris (§ 65, Fig. 36).
138 ZOOTOMY.
40. The parietals (Fig. 35, #2), flat paired bones, fused
together in the middle line, and forming the posterior median
portion of the skull roof: they are perforated in the middle
line by a small aperture or fontanelle (/s) : each parietal
sends off from its postero-external angle a process which
passes outwards, downwards, backwards, and comes in con-
tact with the outer end of the parotic process.
4t. The frontals (/7), immediately in front of the
parietals, to which they are articulated by a straight
transverse coronal suture: anteriorly they terminate at
about the level of the front border of the orbit: they are
separated from one another by the delicate median frontal
suture : in front each frontal gives off a descending process,
which, passing vertically downwards, forms part of the
anterior wall of the orbit.
42. The nasals (za), paired bones extending from the
anterior border of the frontals to the posterior border of the
anterior nasal fossa.
43. The premaxilla (p.m), a median bone forming the
extremity of the snout: it consists of an alveolar portion
bearing the four anterior teeth of each side, and of a nasal
process, which extends upwards, between the anterior nasal
fossx, to meet the nasals.
44. The maxillse, paired bones, continued backwards
from the outer ends of the premaxilla along the sides of the
skull: each consists of an alveolar portion bearing the
remainder of the teeth, a narrow palatine plate, extending
horizontally inwards from the bases of the teeth, and an
ascending process, which extends upwards between the orbit
and the anterior nasal fossa, articulating with the nasal
and prefrontal (§ 48), and forming the lateral wall of the
snout.
45. The jugals, paired bones, each articulated to the
THE LIZARD. 139
corresponding maxilla, and forming the posterior half ot
the ventral boundary of the orbit, and the ventral half of its
posterior boundary : a process of it extends forwards, within
the maxilla, almost to the anterior boundary of the orbit:
its posterior inferior region is produced into a blunt, back-
wardly-directed spur (see § 47).
46. The postorbitals, roofing bones, articulating one
with the outer border of each parietal.
47. Between the outer border of the postorbital, the anterior border
of the quadrate, and the posterior border of the jugal, lie a number of
small, irregular, scale-like bones, which form a continuous bony sheet
behind the orbit, covering the posterior portion of the jugal, to see which
they must be removed.
48. The prefrontal, a small bone, intercalated on each
side between the anterior lateral region of the frontal and the
ascending process of the inaxilla, and extending downwards
to the anterior border of the orbit.
49. The supraorbitals, two rows of small bones form-
ing the upper boundary of each orbit: the inner row,
articulating with the outer border of the frontal, and extend-
ing between the prefrontal in front and the postorbital
behind, consists of four bones, of which the foremost and the
hindmost are considerably smaller than the intermediate
ones: the outer row consists of five small bones,’ the
hindmost of which forms the upper part of the posterior
border of the orbit, while the others bound its dorsal
border.
so. The lacrymal, a small bone perforated by an
aperture for the lacrymal duct, situated just within the
anterior boundary of the orbit, and articulating externally
with the ascending process of the maxilla.
gi. The supratemporals, two bones on each side, of
which the first overlaps the posterior edge of the postorbital,
140 ZOOTOMY.
while the second is a small sickle-shaped bone, closely
applied to the outer surface of the external process of the
parietal.
52. The squamosal, a similar bone to the second or
hinder post-temporal: it lies external to the Jatter and
beneath the first post-temporal, which must be removed to
show it.
53. The quadrate, a stout bone articulating dorsally
with the parotic process, and furnishing at its distal end the
glenoid surface for the articulation of the mandible: it is
strongly curved, convex anteriorly, and hollowed out behind.
54. The basioccipital (Fig. 35, 4.0), a median bone
forming the posterior part of the basis cranii, and furnishing
the middle third of the occipital condyle (g.c).
55. Large paired bones forming the lateral boundaries
of the foramen magnum, furnishing the outer thirds of the
occipital condyle, and continued outwards as the parotic
processes : each consists of the ankylosed exoccipital, (¢.0)
(posterior portion), and opisthotic (0f.0) (anterior portion).
56. A median bone completing the foramen magnum
above, and continued upwards as the vertical sagittal
crest to the parietals: the median portion of this bone is
the supraoccipital (5.0), its lateral portions represent the
epiotics (ef.0.).
57. The prootics (7.0), paired bones continuing for-
wards the combined exoccipitals and opisthotics with which
they articulate posteriorly, thus forming the anterior half of
the side walls of the brain-case: above they articulate with
the epiotics.
58. The pro-, epi-, and opisthotics together form the
auditory capsule: the cavities for the three semi-
circular canals can be seen through them (Fig. 37, @.5.c,
p50, 4.5.0).
THE LIZARD. 141
59. The basisphenoid (Fig. 35, 4.5), continuing forwards
the basioccipital, with which it articulates by a straight
transverse suture, and thus forms the front half of the basis
cranii: its lateral edges give off the outstanding basiptery-
goid processes (4.p/), its front edge is continued into
a delicate bony style, the parasphenoid (2.5), which
underlies the posterior portion of the interorbital septum.
60. The pterygoids, elongated paired bones on the
ventral surfaces of the skull, forming the inner boundaries
of the inferior temporal fossee: each articulates with the
corresponding basipterygoid process, is continued back-
wards and outwards as a process which applies itself against
the inner face of the quadrate, and is continued forwards
to about the middle of the inner edge of the palatine
foramen, sending off at the hinder boundary of that fora-
men a short, outwardly directed process.
61. The transpalatine, or os transversum, a stout
bone extending between the maxilla externally and the
pterygoid internally, and forming, with the process of
the latter mentioned at the end of the last paragraph,
the postero-external boundary of the palatine foramen.
62. The palatine, a flat bone continuing forwards the
anterior process of each pterygoid, and with it completing
the inner boundary of the palatine foramen: anteriorly
it sends a process outwards to the maxilla, thus completing
the palatine foramen in front, and is continued forwards
for a short distance, furnishing the hinder boundary of the
posterior nasal fossa.
63. The vomers (vo), paired bones lying close to one
another in the middle line, in front of the palatines, by
which they are embraced posteriorly, while in front they
articulate with the premaxilla and maxilla ; they are strongly
convex below, concave above.
142 ZOOTOMY.
64. The epipterygoid (¢.f7.) (so-called columella), a
slender rod of bone, lying just in front of and external to
the anterior edge of the prootic: below it articulates with
the pterygoid, above with the prootic.
65. The columelia auris (Fig. 36),a small rod of
combined bone and cartilage, lying in the dorsal wall of the
tympanic recess : its inner end. is inserted into the fenestra
ovalis, a small aperture between the prootic and opisthotic,
while its outer end is, in the entire head, fixed to the inner
surface of the tympanic membrane.
Fic, 36.—Lacerta agilis. The culumella auris (after W. K. Parker)
x 14. The cartilaginous parts are dotted.
e.st, extra stapedial: 7.s¢, infra-stapedial: m.s¢, medio-stapedial :
s.st, supra-stapedial : s¢. stapes.
The columella auris consists of the following distinct parts which
are only to be made out by careful dissection of an entire head: (a) the
stapes, (s/), a small cartilaginous nodule in the fenestra ovalis: (4) the
medio-stapedial (w.s/), a bony bar connected with the stapes, the
ossification from it extending into the latter: {c) a cartilazinous rod
continuous with the distal end of the medio-stapedial, sending eff a
downwardly directed process, the infra-stapedial (2.57), and expanding
at its outer or free extremity into a bar set transversely to the rest of the
columella like the head of a hammer : the lower somewhat pointed end
of this bar is the extra-stapedial (¢.st) : its dorsaiextremity, the supra-
stapedial (s.5¢) is blunt and rounded, and gives off a process which
becomes connected with the auditory capsule.
66. The vagus foramen (Fig. 35, IX, X, XI,), a small
aperture in the combined exoccipital and opisthotic, behind
THE LIZARD. 143
and below the fenestra ovalis, and serving for the passage
of the gth, roth, and r1zth cerebral nerves: the 12th
nerve makes its exit by two small condylar foramina in
the posterior part of the exoccipital (XII).
67. A notch (V) in the anterior border of the prootic,
converted into a foramen in the complete skull by the
membranous side-walls of the anterior moiety of the brain-
case (§ 69); it transmits the 5th and 7th nerves: behind
and below it and also in the prootic is the internal
auditory meatus for the exit of the 8th nerve (VIII).
VI. The foregoing sections, with the exception of the part of § 65
in small type, can be made out on the dried skull: for the
following sections prepare a second skull with great care,
giving special attention to the preservation of the interorbital
septum : boil it in water for a few minutes, and then carefully
remove the roofing bones, the premaxilla, maxilla, vomers,
palatines, transpalatines, and pterygoids: note
68. By the removal of the above-mentioned membrane-bones, the
primordial skull or chondrocranium (Fig. 37) is left, and is seen
to consist of cartilage containing certain endogenous ossifications or
cartilage bones, namely the basi-, ex-, and supraoccipital, the basi-
sphenoid, and the pro-, epi-, and opisthotic.
69. The interorbital septum (igs. 35, 37. 2.0.5), a median vertical
plate of cartilage continued forwards from the anterior border of the
basisphenoid to the junction of the palatines and vomers, whence it
further extends as the septum nasi (s.7) to the end of the snout,
forming the partition between the na-al sacs; the dorsal edge of the
interorbital septum closely underlies the anterior part of the brain,
and gives off, on each side, a partly cartilagincus partly membranous
plate, directed upwards and cutwards, which, uniting behind with the
prootic, above with the skull roof, and in front with the descending
processes of the frontals, furni hes a side-wall to the anterior part
of the brain-case : the interorbital septum and its wings have in trans-
verse section the form ofa V. Paired ossifications in the posterior part
of the membrano-cartilaginons: kull wall. represent the alisphenoids (a/.5).
yo, The nasal capsules (Fiz. 37, 7a), rounded cartilaginous enclo-
sures, lying one on either-side of the septum nasi, of which they are lateral
developments ; each consists of a roof which springs from the dorsal edge:
144 ZOOTOMY.
of the septum, passes almost directly outwards, and then bending down-
wards, furnishes the lateral wall of the capsule, finally turning inwards
towards the base of the septum to form its floor. Each capsule is per-
Fic. 37.—Lacerta viridis. The chondrocranium from above (after
W.K. Parker) X 4. The cartilaginous parts are dotted, the mem-
branous spaces cross-hatched.
al.s, alisphenoid : a.s.c, position of anterior semicircular canal : ¢.7,
external nares : ¢f, epiotic: e.f¢, epipterygoid: 4m, foramen magnum:
fo, fontanelle: 4,s.c, position of horizontal semicircular canal: 2.0.5,
interorbital septum: a, nasal capsule: o.c¢, occipital condyle: f.oc,
parotic process: /r.0, prootic: Z.s.c, position of posterior semicircular
canal; s.2, septum nasi: s.0, supraoccipital,
forated by the anterior nares in front, by the posterior nares below,
by the foramen for the olfactory nerve behind, and above by a cres-
centic slit, the olfactory fenestra,
THE LIZARD. 148
zi. A cartilaginous process, the inferior turbinal, passes inwards
from the anterior part of the lateral wall of the olfactory capsule,
and serves to inerease the surface of the olfactory mucous membrane.
72. The septo-maxillary (Fig. 35, s.#x), a small (paired) nodule
of bone, attached to the side of the nasal septum near its anterior
termination. :
VII. In each ramus of the mandible make out the
following bones :—
73. The articular, forming the proximal end of the
jaw, and furnishing both the cavity for articulation with the
quadrate, and the backwardly produced angle or angular
process of the mandible: from its anterior or distal end,
which is enclosed in a sheath formed by the dentary (§ 76)
the slender Meckel’s cartilage is continued forwards
to the symphysis or point of junctien of the two rami.
74. The angular, a splint-like bone covering the ventral
edge and the lower half of the outer surface of the articular,
but leaving the angular process exposed.
75. The supra-angular, similarly related to the dorsal
edge and the upper half of the outer surface of the articular.
76. The dentary, forming the main part of the distal
portion of the mandible and bearing all the teeth.
77. The splenial, a flat splint applied to the inner face
of the dentary, and fitting, at its hinder end, into a notch
between the articular and the angular.
78. The coronary, a small somewhat conical bone,
forming the upwardly directed coronoid process im-
mediately behind the last tooth: it articulates with the
articular, dentary, and splenial.
VIII. The hyoid apparatus (Figs. 39 and 40) consists
of the following parts :—
79. The body of the hyoid or basi-hyal (Fig. 40,
b,hy), a median flattened rod of cartilage, pointed in front.
80. The anterior cornua (a.co), paired rods of cartilage,
L
146 ZOOTOMY.
extending from the basi-hyal at first outwards and forwards,
and then, almost immediately, outwards and backwards,
curving round the gullet, and finally coming in close
contact with the ventral surface of the auditory capsule.
The short ventral portion of the anterior cornu is the
hypo-hyal, the next considerably expanded portion is
distinguished as the cerato-hyal, the dorsal slender part
is the stylo-hyal.
31. The middle cornua (m.co), paired rods springing
from the basi-hyal just posterior to the anterior cornua, to
which they run more or less parallel: the proximal ends are
ossified. The middle cornua represent the first branchial
arch,
82. The posterior cornua (f.co), paired cartilaginous
rods, springing from the posterior edge of the basi-hyal, and
passing backward and slightly outwards: they represent the
hypo-branchial region of the second branchial arch (see
description of the skate’s branchial arches p. 38, § 41).
$3. A small curved cartilaginous rod attached by fibre to
the dorsal end of each middle cornu: it probably represents
the dorsal or epibranchial region of the second branchial
arch.
1X. In the shoulder-girdle note
54. The coracoids (see dotted outline in Fig. 39), flat
paired bones articulating with the antero-lateral edge of the
sternum: each furnishes the central half of the glenoid
cavity for the articulation of the humerus, and is divided
by a large fenestra into an anterior bar, the precoracoid,
and a posterior portion, the coracoid proper.
85. The scapule, articulating each with the outer
extremity of the corresponding coracoid, and forming the
dorsal half of the glenoid cavity.
86. The suprascapule, continuous with the expanded
THE LIZARD, 147
dorsal extremities of the scapula, and passing’ inwards
towards the vertebral column: they expand gradually to the
dorsal edge, and consist, like the sternum, of partly calcified
cartilage, the remainder of the shoulder-girdle being formed
of true bone.. ;
87. The interclavicle, a cruciform bone, having a long
posterior limb directed backwards over the ventral ‘surface
of the sternum, a short anterior limb, and long lateral limbs
passing directly outward a little anterior to the level of the
glenoid cavities.
83, The clavicles, flat curved bones, articulating in the
middle central line with one another, and with the anterior
limb of the interclavicle, and passing at first directly
outwards, then outwards and upwards to the anterior border
of the suprascapula to which they are united by fibrous tissue,
_X. In the fore-limb make out the following :—
89. The general composition of the limb: it consists of
a proximal division (skeleton of the brachium, § 117 ) con-
taining a single bone, the humerus; a middle division
(skeleton of the antebrachium), containing two bones,
a smaller, internal; the radius, and a larger, external, the
ulna; and a distal division the manus, consisting of a
carpus or wrist, and of five digits.
go. The position of these parts: the humerus is directed
from its proximal or attached end, backwards, upwards, and
outwards ; the ulna and radius pass, from their articulation
with the humerus, downwards and slightly forwards; the
manus has its digits directed forwards and outwards.
gi. If the limb is extended at mght angles to the long
axis of the trunk, it presents a dorsal and a ventral
surface, an anterior or pre-axial and a posterior or
post-axial border; the radius is then seen to be pre-
axial and the ulna post-axial. In the ordinary position the
L2
148 ZOOTOMY.
pre-axial border of the humerus is external, and in the fore-
arm, the distal end is rotated in such a way that while the
pre-axial’ border looks forwards and outwards at the
proximal end of the fore-arm, it looks directly inwards at
its distal end: the manus, being rotated with the fore-arm,
has its pre-axial border inwards.
92. The humerus, an elongated bone, consisting of a
shaft of true bone and of proximal and distal extremities or
epiphyses of calcified cartilage. Its proximal end or
head is rounded, and articulates with the glenoid cavity:
on the pre-axial or radial border the shaft is produced into
a large process, the radial tuberosity, on its post-axial
or ulnar border into a smaller ulnar tuberosity, the latter
being partly formed by the proximal epiphysis. At the distal
end of the humerus is the pulley-like trochlea, divided
into a smaller radial and a larger ulnar articular surface: the
distal end of the shaft has its pre-axial border produced into
the external or radial condyle, its post-axial border into
the internal or ulnar condyle, both processes im-
mediately proximal to the trochlea.
93. The radius, a slender bone consisting of an ossified
shaft and of two calcified epiphyses: the proximal end or
head is disc-shaped and slightly excavated for articulation
with the humerus, the distal extremity is wide from side to
side, concave for articulation with the carpus, and produced
pre-axially into the radial styloid process,
94. The ulna, also formed of shaft and epiphyses; its
proximal end is produced into a blunt upwardly-directed
process, the olecranon, which, along with the actual
proximal end of the bone, furnishes the concave sigmoid
cavity, or articular surface working over the trochlea of the
humerus. The distal end of the ulna is convex and
articulates with the carpus.
THE LIZARD. 149
95. The carpus, consisting of ten small nodular bones,
or rather calcified cartilages; three of these form a proximal
row, the radiale, articulating with the radius, the ulnare,
with the ulna, and the minute intermedium between
them : five others of much smaller size form a distal row
and give attachment one to each of the metacarpals (§ 96) ;
these are called carpalia, and are distinguished by numbers,
that on the radial or preaxial side being carpale 1: a
ninth bone—the centrale,—forms by itself a middle row,
being intercalated between the radiale, ulnare, and second,
third, and fourth carpalia: the tenth bone—the pisiform
or accessory ossicle—is attached to the post-axial side
of the distal epiphysis of the ulna.
-96. The bones of the digits: the first or pre-axial digit
(pollex) consists of three bones, a metacarpal, articulating
with the first carpale, followed by two phalanges ; the
second of a metacarpal and three phalanges ; the third of
a metacarpal and four phalanges; the fourth of a meta-
carpal and five phalanges ; and the fifth of a metacarpal and
three phalanges.
97. The distal or ungual phalanges have something the
form of the horny claws which they support : the remaining
phalanges and the metacarpals are rod-like bones, each
consisting of a bony shaft and a calcified proximal epiphysis,
the distal extremity of the bone being ossified from the shaft.
XI. Observe the characters of the pelvis as follows :—
98. It consists of two tri-radiate bones, the ossa in-
nominata, the dorsal limbs of which articulate with the
sacrum, while the two ventral limbs. unite, each with its
fellow of the opposite side, in the middle line.
99. The acetabulum, a rounded concave pit, at the
junction of the three limbs of the innominate bone, and
serving for the articulation of the femur (§ 1 10).
150 ZOOTOMY.
roo. Each limb of the os innominatum is a separate
bone, the three meeting in the acetabulum in the tri-radiate
suture.
to1. The ilium or dorsal ossification of the innominate
bone: it is an irregular rod, flattened from side to side, and
passing from its sacral articulation downwards and forwards
to the acetabulum, of which it forms the dorsal third.
1oz. The pubis or antero-ventral pelvic bone: it is
somewhat flattened from above downwards, and forms the
antero-ventral third of the acetabulum, whence it takes a
direction downwards, forwards, and inwards to meet its
fellow in the median symphysis pubis (see dotted
outline in Fig. 39).
103. The prepubis, a small rhomboidal nodule a
calcified cartilage, situated in the middle line between the
anterior ends of the pubis.
104. The ischium, or postero-ventral pelvic bone, an
irregular flattened bone, forming the postero-ventral third of
the acetabulum, and passing downwards and inwards to meet
its fellow of the opposite side in the symphysis ischii, a
strip of calcified cartilage being interposed between the two
bones.
to5. The foramen cordiforme, a heart-shaped space
bounded by the pubes in front, and the ischia behind : in the
recent state a median ligament divides it into paired
obturator foramina.
106, The os cloaca, a small rod of bone passing horizontally back-
wards from the symphysis ischiiin the ventral wall of the cloaca (§ 176).
XII. In the hind limb note
107. Its general composition : it consists of three divisions;
a proximal, consisting of a single bone, the femur ; a middle
division or crus, consisting of two bones, a, larger internal,
the tibia, and a smaller, external, the fibula; and a distal
THE LIZARD. 151
division or pes, consisting of a tarsus or ankle, and of five
digits: ;
108. The position of the bones: the femur is directed
from its proximal end forwards, upwards, and outwards ; the
tibia and fibula pass from their articulation with the femur
almost directly downwards; and the digits are directed
forwards and outwards.
109. If the limb is extended at right angles to the long
axis of the trunk, it presents, like the fore-limb (§ 91),
dorsal and ventral surfaces, and pre- and post-axial borders :
it is then found that the tibia is pre-axial, and the fibula
post-axial, and that, in the ordinary position of the parts, the.
pre-axial border, in all three divisions of the limb, is internal.
110, The femur, a stout, slightly-curved bone, consisting
of shaft and epiphyses, the proximal epiphysis being, how-
ever, hardly distinguishable in the adult. The proximal end
of the bone is produced into a prominent ovoidal head for
articulation with the acetabulum ; below and internal (pre-
axial) to the head is a large process representing the lesser
trochanter; the post-axial greater trochanter is almost
obsolete. The distal end of the bone is pulley-shaped, and
forms internal (pre-axial) and external (post-axial)
condyles for articulation with the tibia. Immediately above
(proximal to) the external condyle is a process serving for the
articulation of the fibula, and answering to the external
tuberosity.
111. The tibia, a stout, greatly-curved bone, consisting
of shaft and epiphyses: along its anterior (dorsal) face runs
the longitudinal cnemial ridge, which is especially
pronounced at the proximal end, giving the bone a triangular
transverse section: the proximal end presents two surfaces,
the internal and external tuberosities, for articulation
with the condyles of the femur.
152 . ZOOTOMY.
112. The fibula, a slender bone also consisting of shaft
and epiphyses: its proximal end or head is narrow, and
articulates with the external ‘tuberosity of the femur: its
distal end is widened laterally for articulation with the,
calcaneum (§ 114).
113. Between the femur and the tibia is a thin, cartilaginous plate,
incompletely divided into two portions which answer to the internal
and external semi-lunar fibro-cartilages of man : each half contains
two calcifications or sesamoid bones which, in the dried skeleton,
are seen to be interposed two between each femoral condyle and the
corresponding tibial tuberosity. A large sesamoid bone is situated to
the outer side of this cartilage, and is interposed between the head of
the fibula and the external tuberosity of the femur. There is also a
small sesamoid attached to the ventral surface of the femur, just above
(proximal to) the external condyle. ;
114. The tarsus, consisting of three bones divisible into
a proximal and a distal row : the proximal row consists of a
single large bone, the tibio-fibulare, representing the
ankylosed tibiale or astragalus and fibulare or cal-
caneum ; it presents two concave articular surfaces on its
proximal side for the tibia and fibula ; distally it articulates
by a somewhat pulley-shaped surface with the distal tarsals.
Of these latter—the tarsalia—only two are separate bones
in the adult; one of these (tarsale 3) being a small,
calcified nodule in contact with the proximal end of the
third metatarsal, the other (cuboid or tarsale 4) a larger
bone giving attachment to the fourth and fifth metatarsals.
The first and second tarsalia are ankylosed in the adult with the
proximal ends. cf the corresponding metatarsals ; the fifth tarsale is
absent.
115. The bones of the digits correspond in number and
form to those of the manus, each consisting of a metatarsal
with two, three, four, five, and three phalanges respectively :
THE LIZARD. 153
the metatarsal of the first or pre-axial digit (hallux) and
that of the second articulates with the tibial side of the
tibio-fibulare, the remaining metatarsals with the tarsalia,
as described above (§ 114).
B. Directions for Dissection.
XIII. Make out the following external characters :—
116. The elongated, flat-sided trunk, separated in front
by a slight constriction or neck, from the pyramidal, some-
what depressed head, and. passing behind into the
cylindrical tapering tail, which, in uninjured specimens,
may be nearly twice as long as the head and trunk together.
117. The fore-limbs, springing one on each side from
the anterior end of the trunk, towards its ventral aspect :
when extended at right angles to the trunk, each is seen to
present a dorsal and a ventral aspect, an anterior or pre-
axial, and a posterior or post-axial border ; and to consist of
three divisions, a proximal, the upper arm, or brachium, a
middle, the fore-arm, or antebrachium, and a distal, the
hand, or manus; the latter is terminated by five clawed
digits, of which the first, or pre-axial, is the shortest, and is
distinguished as the thumb, or pollex ; the fifth, or post-axial
digit, is next in size, then comes the second, while the
third and fourth are of nearly equal length (cf. §§ 8997).
118. The hind-limbs, springing one on each side from
the posterior end of the trunk, towards its ventral aspect -
they present the same surfaces and borders as the fore-limbs,
and are similarly divisible into three regions: a proximal,
the thigh or femur; a middle, the shank or crus; and a
distal the foot, or pes : the latter, like the hand, is terminated
154 .ZOOTOMY.
by five clawed digits; of these the first is the shortest,
the second and fifth are of nearly equal length ; the fifth,
however, being the slenderer, and appearing shorter from
the fact that it arises nearer the proximal extremity of
the hand ; the third is considerably longer than the second,
and the fourth slightly longer than the third (cf. §§ 107
—II5).
119. The large mouth, the gape beginning at the end of
the snout and extending backwards nearly to the auditory
apertures (§ 122).
120, The nostrils, or anterior nares, small, rounded
apertures, situated one on each side of the snout, a short
distance from its anterior end.
121, The eyes, situated one on each side of the head,
about midway between the corresponding nostril and
auditory aperture (§ 122): each is guarded by a short, thick
upper eyelid, and a deep, thin lower eyelid, which,
when the eye is closed, covers the greater part of it: within
the eyelids is the thin, transparent nictitating membrane,
which springs from the anterior corner of the eye and shuts
backwards over the eye-ball.
122. The auditory aperture, situated a little posterior
to the extremity of the gape, and nearly as large as the
exposed portion of the eye: stretched over it, a little below
the general level of the head, is the thin tympanic
membrane.
123. The vent, or cloacal aperture (Fig. 39, <2), a
large transverse cleft at the root of the tail.
124. The exoskeleton, consisting of a closely-fitting
armour of epidermic scales: those on the dorsal surface
of the trunk are small, hexagonal in outline, and indistinctly
keeled ; on the ventral surface they are large and are arranged
in eight longitudinal series ; forming the anterior edge of the
THE LIZARD. 155
vent is a large pre-anal plate; the scales on the tail are
elongated, keeled, and arranged in definite transverse series,
giving the tail a ringed appearance ; on the limbs the pre-
axial scales are for the most part large, the post-axial small ;
ae
T. y i —A. Lacerta
ie Of face, sete Ha denies inane Wich enlarged).
After Schreiber.
on the neck they are small, except at its junction with the
trunk, where there is a transverse fold bounded anteriorly by
larger scales; on the head, the scales are for the most part
large, ‘and have a very definite arrangement characteristic
156 -ZOOTOMY.
of the species, many of them receiving distinctive names.
Along the ventral edge of the thigh is a row of apertures
(pori femorales) of a-series of cutaneous glands.
The genus Lacerta is distinguished from Zootoca by the following
characteristics :—Lacerta is oviparous ; it has two small posterior nasal
scales bounding the nostril behind, and teeth on the palate. Zootoca is
viviparous, it has only one posterior nasal scale, and no palatine teeth.
The colouring of the three species is also characteristic. Lacerta
viridis is either green or bluish-green, lighter beneath, more or less
extensively marbled with black, and sometimes having either white
spots, or one or two white streaks on each side. Lacerta agilis
is brown above with black spots, green on the sides, and white beneath.
Zootoca vivipara is olive above, with a white-edged blackish streak on
each side and a central black streak ; the ventral surface is orange and
blue (in summer) spotted with black.
XIV. Place the animal in the supine position (ventral
surface upwards), and make a median incision
through the skin from the chin to the anterior
border of the vent : carefully separate the skin from
the underlying muscles and reflect it right and left ;
this is a matter requiring considerable care,
especially in a fresh specimen, since some of the
muscles are inserted into the ventral scales (§ 124)
and are with difficulty separated from them: the
rectus lateralis (§ 125) is almost certain to be
reflected with the skin. Note
125. The rectus abdominis (Fig. 39, ~7, 7./, m7), a
longitudinal paired muscle which, with its fellow of the
opposite side, forms the median ventral portion of the
muscular body wall. It is divided by transverse fibrous
bands, or inscriptiones tendinez, into segments, the
longitudinal fibres of which are inserted into the anterior
edges of the median ventral scales.
The rectus abdominis consists of three portions: a ventral portion
(rectus ventralis, 7.2’) arising from the last sternal rib and inserted into
the ischium : an external portion (rectus lateralis, 7.7} beginning as a
thin sheet of fibres between the skin and the pectoral muscle (§ 127)
THE LIZARD. 157
O#L
Fic. 39.—Lacerta viridis. The chief muscles of the ventral aspect
of the body (nat. size). On the right side the skin is reflected out-
wards along with the rectus lateralis (7./) and superficial layer of the ex-
ternal oblique (2. ¢x). :
158 ZOOTOMY. A
The position of the hyoidean apparatus, clavicles, interclavicle, cora-
coid, and right half of the sternum, and of the pubes and ischia, are indi-
cated by dotted outlines. On the left side (right in the figure), the my-
lohyoid (7.4y), pectoral (f), and external oblique (.ex) muscles are
removed, as well as the posterior part of the rectus ventralis (rz): by
the removal of the pectoral the left half of the sterum (s¢) is exposed.
ét, biceps : c/, cloacal aperture: ¢.#27, ceratc-mandibularis : a, del-
toid: ¢.7, external intercostal: .y, mylo-hyoid: mx, mandible :
e.ex, obliquus externus, superficial portion: o,ex’, deep portion of
the same: o.4y, omo-hyoid: 0.7, obliquus internus: #, pectoralis :
fer, peritoneum : 7,2, rectus internus: 7./, rectus lateralis : 7r.U, rectus
ventralis : s.c.#, sterno-cleido-mastoideus: s.hy, sterno-hyoideus : sr,
serratus : s/, sternum ; sé’, its posterior prolongations.
and joining the preceding portion at its insertion: and an internal and
posterior portion (rectus internus, 7.7) of triangular form, lying
between the ventral portion and the peritoneum, attached behind to the
puboischiatic ligament and gradually thinning out in front.
126. The obliquus externus (0.x, 0.ex’), a thin sheet
of muscle lying external to the rectus, and with its fibres
taking a direction downwards and backwards (the animal
being supposed to be in the normal attitude).
Tt consists of two layers, a superficial one (0.ex) arising by slips from
the vertebral ribs, and with its fibres ending against the outer border of
the rectus lateralis, with which it becomes indistinguishable posteriorly ;
and a deep portion (9.ex’) lying within (dorsal to) the pectoral, and
similarly related to the rectus ventralis.
127. The pectoralis (f), a large paired muscle arising
from the sternum and sternal ribs, which it largely covers :
the fibres of its anterior part pass outwards and backwards,
those of its posterior portion outwards and forwards, those of
its middle region directly outwards, and, converging, are
inserted into the ventral aspect of the humerus, thus forming
the chief depressor of the arm.
128. The mylo-hyoid (m.hy), a strong sheet of trans-
verse muscular fibres passing from ramus to ramus of the
lower jaw.
THE LIZARD. 159
XV. Cut through the origins of both pectoral muscles
and reflect them outwards: dissect away the
external oblique and note
129. The ribs and sternum, and their relation to the
body walls (see §§ 22-25 and Fig. 39).
130. The external intercostal muscles (¢.2), filling
up the interspaces between the ribs: their fibres run from
any given rib backwards and slightly downwards to its
successor.
131. The obliquus internus (0.2), a thin sheet of
muscle lying between the intercostals externally and the
rectus ventralis internally, and exposed by the removal of
the external oblique : its fibres pass downwards and forwards.
XVI. Make a longitudinal incision through the rectus
ventralis, a litile to one side of the median line,
taking care not to injure the epigastric vein
(§ 138): continue the incision backwards to the
pubes, and forwards by cutting through the
sternum and interclavicle: carefully separate the
epigastric vein from the surrounding tissues and
reflect the body walls. Note
132. The ccelome or body cavity, containing the viscera,
extending in front to about the level of the interclavicle, and
behind continued beyond the anterior boundary of the pubes
as the pelvic cavity.
133. The peritoneum (parietal layer), a thin membrane
lining the ccelome: in the posterior half of the cavity it is
deeply pigmented, in the anterior half colourless, the
boundary line between the black and colourless portions
being perfectly sharp.
134. The liver (Fig. 40, 77), a large, brownish organ,
occupying about the middle third of the body cavity, and
imperfectly divided into right and left lobes.
160 ZOOTOMY.
Tic. 40.—Lacerta viridis. A dissection from the ventral aspect,
showing the alimentary, circulatory, respiratory, and urinogenital organs
(nat. size). The liver (/7) is divided longitudinally (see § XVIII), and
THE LIZARD. 161
its two halves displaced outwards: the alimentary canal is drawn out
to the animal’s left ; the cloaca, with the urinary bladder and posterior
ends of the vasa deferentia, is removed, as also is the right corpus
adiposum. ;
@.co, anterior cornu of hyoid: az, azygos, or cardinal vein: J.hy,
body of hyoid : ¢, caudal vein: c.ad, corpus adiposum : ¢.7, cceliaco-
mesenteric artery, the branches of which have no reference letters, to
avoid confusing the figure, (see § 159) : ce, ceecum: ¢7, carotid artery :
dao, dorsal aorta: du, duodenum: e¢.ju, external jugular vein: ef,
epididymis : efg, epigastric vein : fa, femoral artery : fv, femoral vein :
g-6, gall-bladder: 7.7, internal jugular vein: 2/, ileum: 2.7, inferior
mesenteric arteries : £, kidney : /.ao, left aortic arch: /.az, left auricle:
Zg, lungs: dr, liver: m.co, middle cornu of hyoid: Z.a, pulmonary
artery : Zc, pericardium: 7.co, posterior cornu of hyoid : 7, pancreas :
Pl, pelvic vein: Z4.c, postcaval vein: A¢.v, portal vein: #.v, pulmonary
vein: 7, rectum: 7.au, right auricle: 7.4.a, right hepatic artery: sc,
sciatic vein : sc/.a, subclavian artery : sc/.v, subclavian vein : sf/, spleen :
st, stomach: s.v, sinus venosus: 74, thyroid gland: ¢7, trachea: /s,
testis: v, ventricle.
135. The gall-bladder (g.d), an ovoidal sac, situated at
the lower margin of the right lobe of the liver, and having,
in the fresh state, a green colour, due to the contained bile.
136. The intestine (dz, zl), forming several coils in the
posterior third of the ccelome.
137. The corpora adiposa (c.ad), paired masses of fat,
of somewhat semilunar shape, lying immediately in front
of the anterior boundary of the pelvis, between the peritoneal
and muscular layers of the body-wall.
138. The epigastric or anterior abdominal vein
(epg), a median ventral vessel, running along the inner face
of the body wall, between the peritoneum and the rectus
abdominis: posteriorly it is formed by the union of two
pelvic veins (/), which are attached to the inner borders
of the corpora adiposa and receive veins from them:
anteriorly the epigastric vein enters the left lobe of the liver
on its posterior face : two other abdominal veins bring blood
from the ventral body wall, and enter the liver on its ventral
face at about the junction of its right and left lobes.
M
162 ZOOTOMY.
139. The heart (v, v.az, /.au), situated a short distance
in front of the liver and enclosed in a delicate membrane, the
pericardium. (For the characters of the heart see §$ 197
—200.)
140. The postcaval vein (g7<), a large vessel, usually
gorged with blood, passing from the anterior border of the
liver forwards to the right side of the heart.’
141. The lungs (/g), two transparent, thin-walled sacs
lying one on each side of the postcaval vein between the
heart and the liver (see § 213).
142. More or less of the reproductive organs can
usually be seen even without moving the intestines: by
turning the latter aside the testes of the male (§ 166) and
the ovaries (§ 169) and oviducts (§ 170) of the female,
are displayed.
143. A large vein is also seen, by turning aside the
intestines, lying between the testes or ovaries, and passing
forwards to the postero-dorsal region of the liver; this is the
hinder part of the postcaval (pt).
XVII. Dissect away the mylo-hyoid (.Ay) and under-
lying muscles (amn, ohy, s.hy, Gc.) until the
following structures are laid bare:
144. The trachea (/r), an annulated tube lying in the
middle ventral line of the throat.
1 The injection of the lizard’s vascular system is conveniently done
as follows : Render the animal insensible with chloroform : lay bare the
heart as directed (§ XVI), taking care not to injure the epigastric vein :
slit open the pericardium, and cut off the apex of the ventricle (§ 197).
When the bleeding has stopped, pu h a cannula through the wound into
the cavity of the ventricle and thence into the right aorta (§ 199), and tie
it in place by a ligature round the base of the ventricle. A warm
solution of gelatine coloured with carmine, vermilion, or French blue
{ultramarine) is the best injecting medium ; it is firm enough to pass
through capillaries, so that the whole vascular system, with the excep-
tion of the pulmonary vessels, can be injected at one operation.
THE LIZARD. 163
145. The thyroid gland (7), a whitish, transversely
elongated body on the ventral wall of the trachea, a short
distance in front of the heart.
146. The right precaval vein (Fig. 43, p. 172, pr.0),
situated in the lateral region of the neck, and passing back-
wards towards the right side of the heart (see § 200): it is
formed by the union of three veins; the internal jugular
(Figs. 40 and 43 zw), coming from the lateral region of the
head and bringing blood from the brain, &c. ; the external
jugular (¢.ju), situated in the middle ventral line of the
throat, and at its hinder end turning to the right to join the
internal jugular; and the subclavian (scv), bringing
blood from the right fore-limb.
147. The left precaval, formed by the union of the
left internal jugular and left subclavian veins: the left
external jugular is absent.
148. The position and relation of the hyoidean apparatus
(S$ 79-83).
XVIII. Make a longitudinal vertical incision through
the liver, beginning at its anterior border, a little to
the left (the animal’s left, your right) of the post-
caval, and passing backwards to the right of the
epigastric vein and gall-bladder: in this way the
whole postcaval is left uninjured on the right side,
and the gall-bladder, with its duct (§ 165), and portal
(§ 161) and epigastric veins, on the left.1. Note
149. The stomach (Fig. 40, s¢), hitherto concealed
beneath the liver: it is a tubular organ, of slightly greater
diameter than the intestine, and with thick, muscular walls.
1 This method of dissection is adopted because of the connection of
the liver to the dorsal body-wall by blood-vessels (§§ 163, 164), which are
ruptured if the liver is turned forwards in the ordinary way : in fresh, un-
injected specimens there will of course be a good deal of bleeding, but this
objection does not apply either to injected or to spirit specimens,
M 2
164 ZOOTOMY.
150. The divisions of the intestines: there is no dis-
tinction between the duodenum (dz) or section immediately
succeeding the stomach and the ileum (¢/), or remainder
of the small intestine : the latter, after one or two turns,
passes into the large intestine, or rectum (7), dis-
tinguished by its greater diameter and by having its anterior
end produced on the left side into a small blind pouch or
cecum.
151. The pancreas (fz), an elongated, whitish gland,
situated in the loop between the stomach and duodenum,
and continued forwards to the posterior face of the left lobe
of the liver.
152. The gastro-hepatic omentum, a thin sheet of
peritoneum extending from the dorsal surface of the liver to
the ventral surface of the stomach, and continued backwards
by the duodeno-hepatic omentum, which similarly
connects the liver with the first loop of the intestine.
153. The mesogaster, a fold of peritoneum connecting
the stomach with the dorsal body-wall.
154. The mesentery, a similar fold suspending the small
intestine.
155. The mesorectum, a backward continuation of the
mesentery suspending the rectum.
156. A similar fold attached to the free or dorsal edge of
the right lobe of the liver.
157. The spleen (sf/), a small, red body, lying in the
mesogaster, near the posterior end of the stomach.
158. The dorsal aorta (d.ao), an unpaired longitudinal
artery lying in the middle dorsal line.
159. The cceliaco-mesenteric artery (cm), given off
from the dorsal aorta at about the level of the anterior end
of the right testis, or ovary, and soon dividing into two
trunks, an anterior, the coeliac artery, supplying the
THE LIZARD, 165
stomach, spleen, pancreas, duodenum, and left lobe of the
liver ; and a posterior, the superior mesenteric artery,
which supplies the ileum.
160, The inferior mesenteric arteries (i.m), three small vessels
arising from the aorta at about the level of the pubes and supplying the
rectum,
161. The portal vein (#7), a large vessel lying in the
duodeno-hepatic omentum, parallel to the pancreas: it
receives gastric veins from the stomach, and small
pancreatic veins from the pancreas, and at its distal end
is formed by the union of splenic and mesenteric veins
from the spleen and intestine réspectively.
162, The separate gastric portal veins, two or three small vessels .
taking blood directly from the stomach to the liver.
163. Two small veins taking blood from the dorsal body-wall to the
right lobe of the liver ; by dissecting off the peritoneum they are seen to-
spring from the azygos (cardinal) vein (az), a longitudinal trunk lying .
on the right side of, and close to the vertebral column, which receives
blood from the dorsal region of the trunk, intercostal spaces, &c., and
joins the precaval close to the entrance of the subclavian.
164. The right hepatic artery (7.4.2), a small vessel springing from
the dorsal aorta, and passing parallel to the veins mentioned in § 163 -
to the right lobe of the liver.
165. The common bile-duct, running parallel to the portal vein
and opening posteriorly into the duodenum : at its anterior end it is
formed by the union of the cystic duct from the gall-bladder and the
hepatic duct from the liver itself.
Ln the male :—
166. The testes (Figs. 4o and 41, ¢), two white ovoidal
bodies, that on the right side situated just posterior to the
right lobe of the liver, that on the left somewhat further
back.
167. The epididymis (¢), a whitish, elongated body
attached to the inner face of each testis, and extending
backwards into the pelvic cavity (see § 190).
166 ZOOTOMY.
168, The mesorchium (Fig. 41, s.0), 2 fold of peri-
toneum suspending each testis to the dorsal body-wall: 2
similar fold (4.2) supports the epididymis, and is attached
in front along the line of junction of the colourless and
pigmented regions of peritoneum (§ 133).
a mso
i |
lic, 41.—Lacerta viridis. The male urinogenital organs (nat. size).
‘The ventral wall of the cloaca is removed, the bladder is turned to the
animal’s right, and the peritoneal covering of the left testis and
epididymis is dissected away.
él, urinary bladder : 6 2g, fold of peritoneum supporting epididymis :
cl‘, anterior, and c/*, posterior, division of cloaca: 24, epididymis: 4,
lhidney : #73.0, mesorchium: /, copulatory organs, of which the right is
shown retracted (2) and the left everted (J) : 7.7, retractor muscle of latter:
y, ridge separating anterior and posterior divisions of cloaca : c¢, rectum :
ret', its opening into the cloaca; /, testis: z.g, urinogenital papilla and
aperture: zd, vas deferens,
THE LIZARD. 167
Ln the female :—
169. The ovaries (Fig. 42, ov) situated further back
than the testes, the left being partly within the pelvic
cavity: their surface is raised into hemispherical elevations,
due to the ova.
Fic. 42.—Lacerta viridis. ‘[he female urinogenital organs (nat.
size), The ventral wall of the cloaca, the urinary bladder, the posterior
end of the left oviduct, and the peritoneal investment of the left ovary
and oviduct are removed.
b.lg, broad ligament: c/*, an‘erior, and ¢/?, posterior, division of
cloaca: 4, kidney : 7s.0, mesoarium : od, left oviduct : ca’, its peritoneal
aperture : od”, aperture of right oviduct into the cloaca: ov, ovary:
ur, aperture of ureter.
168 ZOOTOMY.
170. The oviducts (0d), delicate, plaited tubes, lying
dorsal and external to the corresponding ovaries, and
extending backwards into the pelvic cavity : for their further
characters see § 194.
171. The mesoarium (s.0), a fold of peritoneum sus-
pending each ovary to the dorsal body-wall.
172. The broad ligament (4/g), a fold similarly
suspending the oviduct: its anterior line of attachment
corresponds with the junction between the colourless and
pigmented regions of the peritoneum (§ 133).
In both sexes :-—
173. The postcaval vein can now be seen to be formed
by the union of two veins lying within and parallel to
the epididymes or oviducts, and of which the right is
considerably larger than the left (Fig. 40).
174. The whole extent of the lungs can now be seen:
they extend backwards to about the level of the gall-bladder,
the right fitting into a notch on the dorsal face of the right
lobe of the liver.
175. The pleura, a fold of peritoneum connecting each
lung with the dorsal body-wall.
XIX. Dissect off the muscles covering the ventral
surface of the pelvis, and cut away the median
portion of the pubes and ischia: also dissect away
the muscles attached to the inner surfaces of these
bones, portions of which will still be left obscuring
the contents of the pelvic cavity. Note
176. The cloaca (Fig. 41, c/}, ¢?) or posterior division
of the alimentary canal, passing insensibly into the rectum
in front, and opening behind by the vent.
177. The urinary bladder (4/7), a thin-walled sac
attached by its posterior extremity or neck to the ventral
THE LIZARD. 169
wall of the cloaca, and having a bilobed free anterior
“extremity or fundus.
178. The kidneys (Figs. 4o— 42, 2), two dark, reddish-
brown bodies, situated between the dorsal wall of the pelvic
cavity and the rectum: their anterior ends are about on a
level with the corpora adiposa, their posterior ends reach
back a little beyond the level of the vent : they are irregular
in shape, adapting themselves to the form of the cavity in
which they lie, and their tapering posterior ends are closely
applied to one another: they are covered by peritoneum on
the ventral face only’: each consists of two lobes, an anterior
and a posterior.
179. The pelvic veins (Fig. 40, #7) have already been
seen (§ 138) attached to the edges of the corpora adiposa :
traced backwards, each is seen to pass across the ventral
face of the corresponding kidney, and to be united with its
fellow to form a single trunk: this latter, which by its
bifurcation forms the pelvic veins, is the caudal vein (¢) ;
it lies along the ventral aspect of the caudal vertebrae and
brings back blood from the various tissues of the tail.
180. The principal renal portal vein, arising from the
pelvic vein at the point where it turns outwards across the
ventral face of the kidney: it enters the anterior lobe of the
kidney, supplying it with venous blood: the posterior lobe
is supplied by smaller renal portal veins springing from the
hinder part of the pelvic veins.
181. The femoral (fv) and sciatic (sc) veins, two
trunks, the former from the anterior, the latter from the
posterior region of the leg, and opening into the corres-
ponding pelvic vein. ,
182. The two trunks which-by their union form the
postcaval vein (§ 173): the right is considerably the
larger and is directiy continued into the postcaval, while
170 ZOOTOMY.
the left crosses over to the right side to join its fellow at
about the level of the origin of the cceliaco-mesenteric
artery: each trunk receives renal veins from the corres-
ponding kidney, and unites with its fellow just anterior to
the bifurcation of the caudal vein.
183. The femoral artery (fa), passing outwards to
the hind limbs between the femoral and sciatic veins : its
origin from the dorsal aorta is best seen at a later stage.
XX. Cut through the stomach a short distance behind
the heart, and through the rectum a little anterior
to its junction with the cloaca, and remove the
alimentary canal between these two points: open
the various parts of it by longitudinal incisions,
and note
184. The rugee of the stomach, strong longitudinal ridges
into which its mucous membrane is produced, and the
pyloric valve, an annular ridge of mucous membrane
narrowing the aperture between the stomach and duodenum.
185. The vaivule conniventes, delicate longitudinal
ridges on the mucous membrane of the small intestine.
186. The ileo-czecal valve, an annular ridge of
mucous membrane narrowing the aperture between the
small and large intestines, and projecting into the latter.
187. The aperture of the bile-duct in the duodenum.
XXI. Dissect away the peritoneum from the kidneys
and reproductive organs, and open the cloaca by
a ventral longitudinal incision a little to one side
of the middle line, so as not to injure the bladder.
Make out
188. The division of the cloaca by an incomplete ridge
of mucous membrane (Figs. 41 and 42,7) into two sections,
an anterior (c/’) receiving the rectum and a posterior (c/*)
opening externally by the vent.
THE LIZARD. 171
189. The aperture of the urinary bladder in the ventral
"Wall of the anterior division of the. cloaca.
In the male -—
190. The vasa deferentia (Fig. 41, v.@), convoluted
tubes, continuous with the epididymes in front, and passing
backwards to the dorsal wall of the cloaca.
191. The urinogenital apertures (w.g), minute aper-
tures each on the apex of a small papilla on the dorsal wall
of the posterior division of the cloaca.
192. By turning aside the cloaca the ureters may be seen
as delicate tubes situated between the pelvic and renal veins,
and uniting posteriorly with the vasa deferentia.
193. The copulatory organs (), vascular eversible
sacs, lying on the ventral side of the tail, immediately
beneath the skin, and opening into the posterior part of the
cloaca. When everted each is seen to be a somewhat
cylindrical body, with a dilated and bifid apex.
In the female :—
194. The paired apertures of the oviducts (Fig. 42, ed”)
in the dorsal wall of the hinder division of the cloaca, just
posterior to the dividing ridge: anteriorly the oviducts open
into the ccelome by wide apertures (0@”).
195. The apertures of the ureters (wz), small oblique
slits in the dorsal wall of the cloaca, a little posterior to the
oviducal apertures.
196. The ureters themselves are situated as in the male
(§ 192).
XXII. Lay open the pericardium and observe
197. The ventricle (Figs. 40 and 43, 7), a fleshy conical
structure, having its pointed apex directed backwards and
connected to the pericardium by a fine ligament.
198. The right (rau) and left (/aw) auricles, thin-
172 ZOOTOMY.
walled chambers, situated anterior to the ventricle, to the bagg,
of which they are united.
199. The three great arteries, springing from the
base of the ventricle, and passing forwards between the
auricles, closely bound together with connective tissue :
when the latter is dissected away they are seen to have a
twist to the left. Of the three, the pulmonary artery
(Figs. 43 and 44, /.a), lying to the animal’s left, and the
left aorta (/.ac) to the right, are situated ventrally at their
origin, while the right aorta (7.a0) is dorsal to the other
Fic. 43.—Lacerta viridis. The heart, from the dorsal side (X 3).
er, carotid artery: ¢.7v, external, and 2.72, internal jugular vein: ao,
left aorta: az, left auricle: ~.a, pulmonary artery: r.c, right, and
pr.¢, left, precaval vein: ff.c, postcaval vein: 2.7, pulmonary vein:
r.ao, vight aorta : v.az, right auricle: s.a, sinu-auricular aperture: s.c/,
subclavian vein ; s.v, sinus venosus, cut open to show the sinu-auricular
aperture : v, ventricle.
two ; traced forwards the pulmonary artery is seen gradually
to assume a dorsal position, the left aorta becoming ventral
and to the left, the right aorta ventral and to the right.
200, The sinus venosus (s.7’), a chamber situated to
the dorsal side of the right auricle, and seen by turning the
heart aside ; it receives the three great veins ; the right
THE LIZARD. 173
ne]
ecaval ( gr.c) passing directly backwards, the postcaval
. directly forwards into it, while the left precaval (r.c),
on reaching the neck, turns medianwards and passes across
the dorsal wall of the left auricle.
201. The division of the pulmonary artery as it pierces
the front wall of the pericardium into a right and left trunk,
each of which passes at first outwards and then backwards
to the corresponding lung.
202, The pulmonary veins (4.v), bringing the blood
from the lungs, and uniting into a short common trunk
which enters the left auricle on its dorsal wall.
Fic. 44.—Lacerta viridis. The aortic arches, supposed to be
removed close to their origin from the heart (nat. size). ,
cr, carotid artery: d.ao, dorsal aorta: /.ao, left aortic arch: p.a, pul-
monary artery: 7.20, right aortic arch : s.c/, subclavian artery.
203. Leaving the pericardium, the two aortic arches
(Fig.,44) separate from one another, the right arch turning
to the right side, the left to the left: traced outwards they
are seen to bend round the cesophagus and to unite with one
another on the ventral face of the vertebral column to form
the dorsal aorta (¢.ao).
204. The carotid arteries (cr), arising together from
the right aorta just where it diverges from the left: each
carotid passes outwards, parallel with the corresponding
aortic arch, with which, at its distal end, it anastomoses
174 ZOOTOMY,
(ductus Botallt): shortly before this union the carotid arte,
proper is given off and passes forwards to the head. i
205. The subclavian arteries (s.c/), arising from the
right aortic arch just before its junction with the left, and
passing directly outwards to the fore-limbs.
XXIII. Remove the heart, and open its various
cavities under water: first placing it on its ventral
face and opening the sinus venosus from the dorsal
side, and afterwards placing it on its dorsal face
and opening the auricle and ventricle from the
ventral side. Note
206. The thin, smooth walls of the sinus venosus.
207. The sinu-auricular aperture (Fig. 43, s.aw), a
transverse slit placing the sinus venosus in communication
with the right auricle, and guarded by the two-lipped sinu-
auricular valve.
208, The septum auricularum, a vertical partition
separating the auricles from one another.
209. The musculi pectinati, forming a network on
the inner surface of the walls of the auricles.
210, The auriculo-ventricular aperture, placing
both auricles in communication with the ventricle, and
divided into two by the free edge of the septum auricu-
larum : guarding the aperture is the auriculo-ventricular
valve, consisting of two semi-lunar flaps, a right gand a
left, placed back to back in such a way that each shuts
across one half of the auriculo-ventricular aperture.
211. The thick, spongy walls and small cavity of the
ventricle.
212. The origins of the great arteries: the pulmonary
artery arises to the left of the two aorta, and its aperture is
separated from theirs by a muscular partition: the apertures
of the aortic arches are in the same vertical plane, that of
THE LIZARD. 175
ve left being ventral to that of the right: all three arterial
ertures lie to the left of the auriculo-ventricular aperture.
XXIV. By the removal of the heart, the lungs are
thoroughly exposed; note in them the following
points :—
213. Each lung is a fusiform sac, very thin in its posterior
half, much thicker anteriorly: on cutting it open, the wall
is seen to be raised into a network of delicate ridges, pro-
ducing a honey-combed appearance: the network is closer
and the ridges more marked at the anterior than at the
posterior end of the lung.
214. The bifurcation of the trachea into two very short
tubes, the bronchi, which communicates each with the
corresponding lung by a small aperture a short distance
from its apiculate anterior end.
215. The complete cartilaginous rings of the trachea and
bronchi.
XXV. Slit up what remains of the gullet along one
side, and continue the incision forwards, through
the floor of the mouth, close alongside the inner
edge of the mandible; turn aside the floor of the
mouth so as to expose the oral cavity: if the
latter is not sufficiently displayed, part of the
mandible may be cut away with bone forceps.
Observe
216.°The tongue, a narrow, elongated, fleshy organ on
the floor of the mouth, bifid in front.
217. The glottis, or aperture of the trachea into the
mouth, a small longitudinal slit, placed at the summit of a
rounded prominence in which are contained the cartilages
of the larynx.
218. The small, conical teeth, arranged in a single series
round the upper and lower jaws (premaxillary, maxillary,
176 ZOOTOMY.
and mandibular teeth) : there is also a small patch of teeth.
on each side of the roof of the mouth (palatine teeth). “=
219. The posterior mares, considerable apertures
situated a little behind the end of the snout and
separated from one another by a vertical partition
supported by the vomers (§ 63).
Slightly in front of the posterior nares are two minute slit-like aper-
tures, each leading into a small pigmented sac (Jacobson’s organ)
lying under the nasal sac. The relations of these parts are best seen in
a transverse section of the snout.
220. The Eustachian pits ; large paired diverticula of
the dorsal wall of the pharynx, continuous with the tym-
panic cavities, which are bounded externally by the
tympanic membranes.
221, The position of the columella auris in the tympanic cavity,
and its relations to the fenestra ovalis and tympanic membrane, may
now be made out (see § 65, p. 142). Also remove an eye and note a
series of thin scale-like bones (sclerotic plates) surrounding the border
of the sclerotic.
XXVI. Break away the roof of the skull with bone
forceps so as to expose the brain: this may be
done without first dissecting off the skin which
adheres very closely to the subjacent bones. Re-
move the brain, taking especial care not to injure
the olfactory lobes (§227, Fig. 45, o/f), and, after
preservation in spirit, place it under water in a
small dissecting dish, and make out its parts as
follows :—
222. The medulla oblongata (Fig. 45, 1.0), or pos-
terior division of the brain, continued insensibly behind
into the spinal cord: it is about double the diameter of
the cord, and exhibits a strong ventral flexure.
THE LIZARD. 177
Fic. 45.—Lacerta viridis. The brain; A, from above, with the
left cerebral hemisphere (c.2) and optic lobe (0./) opened; B, from
beneath; ¢, from the left side ; D, in longitudinal vertical section.
N
178 ZOOTOMY.
a.c, anterior commissure: ag.s, aqueduct of Sylvius: ¢4, cerebellunagg:,
é.¢, crura cerebri: ¢.4, cerebral hemispheres : ch.f, choroid plexus : ig
corpus striatum: /.w, foramen of Monro: zu, infundibulum: m.o,
medulla oblongata : o.c, optic chiasma: 0./, optic lobes: o/f, olfactory
lobes: 0.4, optic tracts: o.v, aperture between aqueduct of Sylvius
and optic ventricle : #.c, posterior commissure : px, pineal body: pu’,
pituitary body: v3, third ventricle: v.4, fourth ventricle: 7—A/J,
cerebral nerves,
223. The cerebellum (cd), a small semicircular flap
covering the anterior part of the medulla oblongata on the
dorsal side.
224. The fourth ventricle (v7.4), a cavity on the
dorsal surface of the medulla, roofed over in front by the
cerebellum, but for the rest of its extent covered only by
the pia mater, a delicate membrane investing the brain
and spinal cord.
225. The optic lobes, or corpora bigemina (o./),
two large rounded elevations on the dorsal surface of the
brain, immediately in front of the cerebellum: they consti-
tute the dorsal portion of the mid-brain, the ventral
region of which answers to the crura cerebri (¢.c).
226. The cerebral hemispheres (¢./), large, pyramidal
paired masses, immediately in front of the optic lobes,
against the anterior faces of which they abut closely: they
are in close contact with one another by their flat inner
faces, and are pointed in front.
227. The olfactory lobes (o/f) paired, club-shaped
bodies continued forwards from the anterior ends of the
cerebral hemispheres: from their dilated anterior ends are
given off the olfactory (first cerebral) nerves to the nasal
sacs.
228. The pineal body (x), a small, rounded mass in
the middle line of the dorsal surface of the brain, at the
junction of the cerebral hemispheres and optic lobes.
229. The pituitary body (7)), a rounded mass situated
THE LIZARD. 179
yin the middle line of the ventral surface of the brain, imme-
“diately under the pineal body, and attached to an elevation,
the infundibulum.
230. The thalamencephalon, seen by slightly separat-
ing the posterior ends of the cerebral hemispheres as a
rounded median mass, interposed between the hemispheres
and the optic lobes: the infundibulum is a ventral, back-
wardly-directed prolongation of the thalamencephalon.
231. The optic chiasma (0.c), an x-shaped body situated
immediately anterior to the infundibulum, and consisting
of the optic tracts (0./), which pass backwards and slightly
upwards on either side of the infundibulum to the anterior
ventral region of the optic lobes, and of the optic (second)
nerves (II), which, becoming free from the brain, pass
forwards and outwards to the eyes.
232, The third nerve (III), arising from the ventral surface of the
mid-brain.
233. The fourth nerve (IV), arising from the dorsal surface of the
medulla oblongata, just in front of the cerebellum.
234. The fifth nerve, or trigeminal (V), arising from the ventro-
lateral region of the medulla.
235. The sixth nerve (VI), a small nerve arising from the ventral
region of the medulla, not far from the middle line.
236. The seventh nerve (VII), arising in common with the eighth
from the lateral surface of the medulla, just posterior to the fifth.
237. The eighth, or auditory nerve (VIII), arising in common
with the seventh.
238. The ninth nerve, or glossopharyngeal (IX), arising imme-
diately behind the eighth, and at a somewhat lower level.
239. The tenth nerve, or vagus (X), arising just posterior to the
ninth, by three or four separate roots.
240. The eleventh nerve, or spinal accessory (X1), arising from
the spinal cord, and passing forwards, receiving fibres as it goes, to the
medulla cblongata, which it finally leaves immediately behind the
vagus.
241. The twelfth nerve, or hypoglossal (XII), arising a little
behind the eleventh from the ventral surface of the medulla.
N 2
180 ZOOTOMY.
XXVII. Carefully cut into the cerebral hemisphere and,
optic lobe of one (say the left) side,! and remove
the roof of the cavities exposed : observe:
242. The optic ventricle (Fig. 45, a), a small cavity in
the thick-walled optic lobe: in its inner wall is a small
aperture (0.v), which leads from the aqueduct of Sylvius
(§ 246).
243. The lateral ventricle, a considerable cavity
in the cerebral hemisphere, extending in front into the
olfactory lobe: its dorsal and inner walls are thin ; its ventro-
lateral wall is greatly thickened so as to form a well-marked
eminence, the corpus striatum (4s).
244. The choroid plexus (c/.f), a plaited fold of con-
nective tissue, abundantly supplied with blood-vessels, lying
in the postero-internal angle of the lateral ventricle.
245. Traced downwards, the choroid plexus is seen to
pass through the foramen of Monro (D, fm), a small
aperture in the posterior part of the inner wall of the lateral
ventricle, and communicating with the third , ventricle
(§ 248): to see it the corpus striatum must be drawn aside.
XXVIII. Remove the left half of the cerebellum and
enough of the left optic lobe and cerebral hemi-
sphere to bring into view
246. The aqueduct of Sylvius (ag.s), a passage
bounded below by the crura cerebri and above by the optic
lobes, in free communication with the fourth ventricle pos-
teriorly, and communicating by the small lateral apertures
already seen (§ 242) with the optic ventricles, with which it
forms the ventricle of the mid-brain, or mesoccele.
247. The optic thalami, paired masses of which the
thalamencephalon is composed.
) If another specimen is to be dissected, this may be done on both
sides, and a longitudinal section (¢ NXIX) made of the second brain.
THE LIZARD. 181
1 pe 248. The third ventricle (v. 3), a narrow vertical slit
between the optic thalami, continuing forwards the aqueduct
of Sylvius: it communicates in front by the foramen of
Monro (fim), already seen (§ 245), with the lateral ventricle.
249. The anterior commissure (a.c), a small, trans-
verse band of white nerve fibres, passing transversely
between the two optic thalami, below and somewhat in front
of the foramen of Monro.
250. The posterior commissure ( #.c), a similar trans-
verse band connecting the optic thalami at their junction
with the mid-brain.
XXLX. Cut away the remainder of the left side of the
brain so as to get a longitudinal vertical section of
the whole organ (Fig. 45, D). Note:
251. The continuity between the fourth ventricle, aque-
duct of Sylvius, and third ventricle, and the precise position
of the apertures leading into the lateral and optic ventricles.
252. The downward continuation of the third ventricle
into the infundibulum.
253. The general relations of the parts seen in the
previous dissection.
THE PIGEON,
(Columba livia.)
A.—THE SKELETON.
I. Two skeletons should be examined, one of an adult
bird, the other of a nestling two or three weeks
old, the latter being especially useful for the skull,
sacrum, pelvis, &c., which, owing to the early
ankylosis of the bones, cannot be satisfactorily
made out in the adult. The adult skeleton is best
prepared by maceration, that of the nestling may
be either macerated for a short time, or subjected
to the action of boiling water for a few seconds:
it must be kept in alcohol or glycerine and water,
or prepared by the glycerine jelly process. In the
adult skeleton the cervical vertebree (§ 1) should
be separated from one another and strung together
in order: the limb bones should be separated on
one side, on the other left attached by their liga-
ments: the ribs (§ 25) are best separated at the
junction of their vertebral and sternal portions,
the former being left attached to the vertebra, the
latter to the sternum ; a longitudinal vertical sec-
tion should be made of the skull with a fine
fret-saw.
THE PIGEON. 183
II. Notice, first of all, the general composition of the
skeleton: it consists of:
1. The vertebral column, distinguishable into (a)
thirteen or fourteen cervical vertebra, forming the
skeleton of the neck, and the last two of them bearing well-
developed ribs, which do not unite with the sternum; (4)
the four anterior thoracic vertebrae, all united with one
another and bearing ribs which articulate with the sternum ;
(c) the compound sacrum, consisting of several vertebra
ankylosed together, and giving attachment to the pelvis; of
these ankylosed vertebrz the first is thoracic, bearing ribs
which unite with the sternum, the next two or three are
lumbar, the next three or four sacral, and the remaining
six caudal; (¢) the free caudal vertebrz, about six in
number ; and (e) the pygostyle or ploughshare bone, a
laterally compressed plate, forming the posterior termination
of the vertebral column.
2. The skull, consisting of (a) the brain-case and upper
jaw; (0) the lower jaw or mandible ; and (c) the hyoid
or tongue-bone.
3. The sternum, a broad, keeled plate, giving attach-
ment to the five pairs of thoracic ribs.
4. The skeleton of the wings or fore-limbs, articulat-
ing with the shoulder-girdle, which consists of two bones
on each side, the ventral one articulating with the sternum,
and connected with its fellow by the U-shaped furcula or
merrythought.
s. The skeleton of the hind-limbs or legs, articulating
with the pelvis or hip-girdle, the two halves of which are,
in the adult, firmly united with the sacrum.
III. Examine the last cervical vertebra, and make out
the following parts :
6. The centrum or body of the vertebra, elongated
we
184 ZOOTOMY.
from before backwards, flattened from above downwards at,
its anterior end, almost square in section posteriorly: its
anterior and posterior faces by which it articulates with the
preceding and succeeding vertebra respectively are cylin-
droidal, the anterior face being concave from side to side and
convex from above downwards, the posterior face convex
from side to side and concave from above downwards.
7. The neurapophyses, upwardly directed processes,
rising one on each side from the dorsal surface of the cen-
trum, and meeting with one another in the middle line above,
forming the neural arch, thus helping to close in the
neural canal in which the spinal cord is contained. Each
neurapophysis is slightly excavated in front, considerably
excavated behind, so that in the articulated vertebral column
a series of intervertebral foramina are left between
successive neurapophyses and serve for the exit of the
spinal nerves.
8. The neural spine, a median vertical plate arising
from the dorsal surface of the neural arch.
g. The anterior zygapophysis, a stout forwardly
directed process, arising from the front edge of each neura-
pophysis and bearing a flat articular facet which looks
upwards and inwards, and is overlapped by the posterior
zygapophysis of the vertebra next in front.
to. The posterior zygapophysis, a similar, back-
wardly directed process arising from the hinder edge of each
neurapophysis: it bears an articular facet which looks
downwards and outwards, and overlaps the anterior zygapo-
physis of the vertebra next behind.
11. The transverse process, a stout, outwardly
directed rod springing from the outer face of each neurapo-
physis: it bears on its under surface a small tubercular
facet for the tubercle of the rib (§ 14).
THE PIGEON. 185
12, The capitular facet, a small articular surface on the
lateral surface of the centrum near its anterior end, and
giving articulation to the head of the rib (§ 14).
13. The hypapophysis, a vertical downwardly directed
process, proceeding from the middle vertical line of the
centrum.
14. The ribs, small curved bones articulating, one on
each side, with the vertebra, and tapering from their proxi-
mal to their distal ends. The proximal end is divided into
two processes, one ventral, the head or capitulum, which
articulates with the capitular facet on the centrum, the other
dorsal, the tubercle, which articulates with the tubercular
facet of the transverse process.
15. The uncinate process, a small flat plate of bone
given off from the posterior border of each rib, and directed
backwards and upwards.
IV. In the remaining cervical vertebrze note:
16. The gradual diminution from behind forwards of the
neural spines, transverse processes, and hypapophyses, and
the gradual elongation of the centra as far as about the third
or fourth vertebra.
17. In the penultimate vertebra the rib is much smaller
than in the last, has no uncinate process, and its proximal
end is indistinctly divided into head or tubercle.
18, The absence of free ribs in the remaining vertebree :
the apparent transverse process is, however, perforated by
an aperture, the vertebrarterial canal, for the passage of
the vertebral artery (Fig. 54, p. 232, v7), and the part of the
‘transverse process external to this aperture represents a
cervical rib, the head and tubercle of which have anky-
losed with the centrum and transverse process respectively.
19. The characters of the second vertebra or axis; it is
considerably reduced in all dimensions: the anterior zyga-
186 ZOOTOMY.
pophyses are very small and placed low down on the arch:
the anterior face of the centrum is somewhat excavated and
gives off dorsally a conical peg, the odontoid process,
which bears an oblique articular facet on the ventral surface
of its free end, for articulation with the atlas (§ 20).
In the young bird the odontoid is a separate bone,
20. The characters of the first vertebra or atlas: it is
very small and is reduced to a mere ring, the centrum being
no thicker than the arch: the centrum is crescentic, the
concavity of the crescent being upwards, and bearing an
articular facet for the odontoid process of the axis, the two.
together forming a concave articular cavity for the occipital
condyle (§ 35): there are no anterior zygapophyses and the
posterior zygapophyses are small.
21. The mode of articulation of contiguous centra: they are united
by rings of cartilage, their adjacent faces being separated by a closed
space (synovial capsule) : each intervertebral ring is produced inwards
into a thin plate of cartilage, the meniscus, which is perforated in the
centre, and forms a vertical partition dividing the synovial space into an
anterior and a posterior divi-ion: a delicate ligamentous cord, the
ligamentum suspensorium, passes from centrum to centrum through
the aperture in the meni-cus,
V. In the thoracic vertebrz note:
22. The fusion of the first four into a single mass by
the ankylosis of the centra, zygapophyses, and transverse
processes.
23. The fusion of the fifth with the compound sacrum:
its large transverse processes abut against the ilia, with
which the proximal ends of its ribs are also united.
24. The large hypapophysis of the first thoracic
vertebra, dividing below into two divergent laminz.
25. The thoracic ribs: each is divided into two parts
by a transverse articulation,—a dorsal section, the vertebral
‘THE PIGEON. 187
rib, having all the characters of the last cervical rib ($$ ry,
15), a ventral section, the sternal rib, a straight flat
bone, making an obtuse angle with the vertebral rib, and
articulating at its lower end with a facet on the sternum.
Vic, 46.—Columba livia, The sacrum of a nestling (about fourteen
days old), viewed frorn beneath (x 2).
On the left side (right of the figare) the first two caudal ribs (c.7) are
removed, so as to show the dorsal transverse processes (/7.p") : the sub-
sequently ossifying membrane which fills up the intervals between the
transverse processes is also removed on the same side: the last thoracic
vertebra is not shown, not yet haviug united with the sacrum.
The cartilaginous parts are dotted.
c.1, ossified centrum of first, and ¢.7, of seventh caudal vertebra :
¢.7, first caudal rib: 4.1, centrum of first, and 73 of third lumbar
vertebra: 5.1, centrum of first, and s.3 of third sacral vertebra: ir /,
transverse process of first lumbar, ¢.g’, of second sacral, and ¢r.2",
of first caudal vertebra,
VI. In the remaining vertebre entering into the com-
position of the compound sacrum make out:
26. The two or three lumbar vertebra (Fig. 46, 21—
7. 3), immediately succeeding the fifth thoracic: each has a
stout wide body, short strong transverse processes abutting
188 ZOOTOMY.
against the ilia (§ 107), rudimentary neural spine, and no
hypapophysis.
27. The three or four sacral vertebre (s5.1—s.3),
closely resembling the lumbar, but having transverse pro-
cesses, in the form of thin flat plates passing outwards from
the dorsal ends of their neural arches and abutting against
the ilia: in the adult, the transverse processes of succes-
sive vertebrae are fused together, the original spaces between
them being marked only by two rows of small apertures.
28. The first caudal vertebra (¢1), like the sacral,
but having, in addition to the lamellar transverse processes
springing from its arch, a pair of strong outstanding pro-
cesses—caudal ribs (c7)—from its centrum, which also
abut against the ilia: a distinct passage is left between the
two processes.
29. The remaining ankylosed caudal vertebra, six in
number: in these the centrum becomes progressively
smaller, and in all but the first of them (second caudal)
there is no distinction between rib and transverse process.
30. In the young bird the sacrum is a continuous carti-
lage, in which the constituent vertebrae are only marked by
the transverse processes, and by the median ventral ossifi-
cations for the centra (Fig. 46).
VII. In the remainder of the vertebral column, note:
31. The free caudal vertebra, each having a short
centrum, a well-marked spine, and long, flat, outstanding
transverse processes: in the last two there is alsa a
distinct hypapophysis.
32. The pygostyle or ploughshare bone, an irregular
vertical plate of bone, with its axis almost at right angles to
that of the free caudal vertebree : it forms the hinder termi-
nation of the vertebral column and supports the uropygium
(§ 121, p. 209).
THE PIGEON. 189
Fic. 47.—Columba livia, The skull of a young bird (about six
weeks old). A, from above; B, from beneath ; C, from the left side
(nat. size).
The cartilaginous parts are distinguished by dotting.
al.s, alisphenoid : an, angular: ar, articular: 6.0, basioccipital :
@, dentary: é0, exoccipital: e, aperture of Eustachian tube: fm,
foramen magnum: fy, frontal: 7.0.5, interorbital septum : x, jugal:
Zc, lacrymal : /b.5, lambdoidal suture : #7. eh, mesethmoid : mx, maxilla:
mx.p, maxillo-palatine process: xa, ma‘, na", nasal: o.c, occipital
condyle: or fr, orbital plate of frontal: ga, parietal: ga.s, para-
sphenoid : #v, palatine : p.m, premaxilla: g¢, pterygoid : gu,quadrate :
S.an, supra-angular : 5.0, supraoccipital : sg, squamosal: ‘zy, tympanic
cavity : II—XII, foramina for cerebral nerves. ;
190 ZOOTOMY.
VIII. In the skull make out:
33- The rounded brain-case, greatly encroached upon
in front by the large orbits or cavities for the eyes, and
continued in front into the slender tri-radiate beak.
34. The foramen magnum (Fig. 47, fm) a large
rounded aperture in the ventral wall of the hinder end of
the brain-case.
35. The occipital condyle (o.c), a small hemispherical
elevation on the lower or anterior margin of the foramen
magnum.
36. The lambdoidal ridge, a transverse ridge, a little
above and parallel to the upper border of the foramen mag-
num: it serves for the attachment of some of the muscles
of the neck,
37. In the young bird the foramen magnum is bounded
by four distinct bones, one ventral, the basioccipital (4.0),
one dorsal, the supraoccipital (s.0), and a pair lateral,
the exoccipitals (e.0); the supraoccipital is bounded above
by the lambdoidal suture (/d.s), which separates it from
the parietals, and is represented in the adult by the lamb-
doidal ridge.
38. A median longitudinal groove on the dorsal surface of
the skull, passing behind into a low ridge which unites with
the centre of the lambdoidal ridge : it marks the position of
the obliterated suture between the right and left parietals
and frontals,
39. In the young bird the parietals (fa) and frontals
(/r) form two distinct pairs of bones, the former extending
a short distance forward from the lambdoidal suture, while
the frontals furnish all the anterior part of the roof of the
brain-case, and are continued forwards between the orbits,
to each of which the corresponding frontal furnishes a
supraorbital ledge.
THE PIGEON. 19I
40. In the young bird the antero-ventral region of each
side of the brain-case is formed by a separate bone, the
Squamosal (sg), bounded by the frontal and parietal above
and behind, by the alisphenoid (§ 42) in front, and by the
exoccipital below.
41, At the posterior margin of each orbit the curved side-
walls of the skull turn sharply inwards, forming a thin plate
of bone—the orbital plate—which constitutes at once the
anterior wall of the brain-case and the posterior wall of the
orbit.
42. In the young bird the orbital plate consists of two
parts,—an upper and smaller portion, the orbital plate of
the frontal (o7,/r), an inturned portion of the latter
bone, and a lower and larger portion, forming a distinct
bone, the alisphenoid (a/.s).
43. The interorbital septum (¢2.s.), a thin vertical plate
of bone separating the orbits from one another, and uniting
posteriorly with the orbital plates.
44. The anterior part of its interorbital septum consists,
in the young bird, of a separate bone, the mesethmoid
(m.eth), the posterior part representing the presphenoid.
45. In the dried skull the orbits are placed in com-
munication with one another by two large vacuities, or
interorbital fenestra, situated one above the other, and
occurring partly in the orbital plates, partly in the inter-
orbital septum: in the recent state they are filled in
by membrane,
46. In the membrane filling the uppermost interorbital
fenestra there is a median aperture, the olfactory fora-
men, for the transmission of the olfactory nerve from the
brain : this is continued on each side by a groove, visible in
the dried skull, which runs along the dorsal edge of the
interorbital septum and, at its anterior end, passes into an
192 ZOOTOMY.
aperture, which communicates with the nasal cavity, and
serves for the passage to that cavity of the olfactory nerve.
47. In the membrane filling the lower interorbital
fenestra there is a median aperture, the optic foramen
(11), for the transmission of the optic nerves from the brain
to the eyes.
48. The tympanic cavity (4), an irregular depression,
just behind the postero-inferior angles of the orbit, its
opening looking upwards and forwards: it is bounded by
the squamosal above, by the exoccipital behind, and by the
basitemporal (§ 50), beneath.
49. The parasphenoid (2.5), or basisphenoidal
rostrum, an elongated thickened rod of bone, pointed in
front, underlying the interorbital septum with which it is
completely ankylosed in the adult: in the young bird it is a
separate bone. At its base, it bears, on each side, a small
facetted basipterygoid process, for the articulation of
the pterygoid (§ 62).
50. The basis cranii, or floor of the skull, extending
from the lower margin of the foramen magnum to the base
of the parasphenoid, and bounded externally by the lower
margin of the tympanic cavity: in the young skull the
hinder part of the basis cranii is formed, as already seen
(§ 37), by the basioccipital ; in front of this isa large median
‘bone, the basisphenoid, underlaid and concealed in the
entire skull by the basitemporal, a large flat plate of
membrane bone, which extends forwards to the base of the
parasphenoid and outwards so as to form the ventral walls
of the tympanic cavities.
51. The anterior edge of the basitemporal projects over the base of
the rostrum in the form of a delicate lamina of bone, between which
and the rostrum is a small space into which the two Eustachian tubes
open: a bristle may therefore be passed from this common Eustachian
aperture (¢z) into either tympanic cavity (§§ 298, 318).
THE PIGEON. 193
52. The character of the cranial bones as seen in a longi-
tudinal section of the skull: they consist of a dense but
very thin outer layer or external table, of a similar inner
layer or internal table, and of an intermediate spongy
substance or diploé: the latter is especially thick in the
anterior part of the frontals and in the basi- and para-
sphenoid.
53- The hollows on the inner surface of the brain-case
for the lodgment of various parts of the brain: the basis
cranil is deeply concave from before backwards for the re-
ception of the medulla oblongata (Fig. 58, m0): in the
frontal region, or dorsal portion of the brain cavity, is the
large cerebral fossa for the reception of the cerebral
hemisphere (Fig. 58, ¢.4); below this and separated from it
by a well marked horizontal ridge of bone is the rounded
optic fossa for the optic lobe (Fig. 58, 0./); behind and
below these two hollows is the cerebellar fossa for the
cerebellum (Fig. 58, ), limited in front by a ridge—the
tentorial ridge—which passes obliquely upwards and
backwards from the basis cranii to meet its fellow of the
opposite side in the roof of the skull somewhat anterior to
the lambdoidal ridge.
54. The auditory capsule, a considerable thickening
of the brain-case just external to the foramen magnum, and
encroaching upon the optic and cerebellar fosse: it is
limited above by a well marked semicircular ridge, which
indicates the position of the anterior semicircular
canal, a swelling at its anterior end marking the position of
the ampulla of that canal (see figure of cod’s auditory
organ, p. 123): within the arch of this canal is another
ridge, indicating the inner (anterior) portion of the pos-
terior semicircular canal.
The position and relations of the three semicircular canals are best
re)
194 ZOOTOMY,
seen by cutting away with a penknife the outer table of the cranial
bones in the auditory region, and then carefully removing the diploé ;
the canals are surrounded by a dense layer of bone, which, isolated
in the way described, forms the bony semicircular canals, precisely
corresponding in form and position with the contained membranous
canals. The anterior canal is considerably larger than the other two ;
the plane of the posterior canal is at right angles to that of the anterior,
and its ampulla is on its lower or outer (= posterior) end; owing to
this peculiarity in the position of the posterior canal, it crosses at right
angles the horizontal canal, which has the normal position (see descrip-
tion of cod’s auditory organ, pp. 122, 123, § 182).
55. In the young bird the main part of the auditory
capsule is formed by a single distinct bone, the prootic:
two other ossifications are however formed, one upper
and posterior, the epiotic, which early fuses with the supra-
occipital, another ventral and posterior, the opisthotic,
which becomes united with the exoccipital.
56. A little below the swelling for the ampulla of the
anterior semicircular canal, on the inner surface of the skull,
are two small apertures, for the passage of the seventh
(facial) and eighth (auditory) cerebral nerves.
57. Below these apertures, and separated from them by a
ridge of bone, is a small oval fossa with an aperture (1x, x)
at the bottom of it, which leads directly on to the outer
surface of the skull, and serves to transmit the ninth
(glossopharyngeal), tenth (vagus), and eleventh (accessory)
cerebral nerves,
58. A small aperture within and behind the above is the
condyloid foramen (x11); it also leads on to the exterior
of the skull and transmits the twelfth (hypoglossal) cerebral
nerve.
59. Immediately below the optic fossa are two adjacent
apertures which lead on to the anterior surface of the
orbital plate, and serve for the passage of the fifth nerve
(trigeminal),
THE PIGEON. 195
60, The quadrate (gz), a short, stout, irregular bone,
articulating by a double head with two facets in the dorsal
region of the tympanic cavity, the upper of the two facets
being furnished by the squamosal, the lower by the prootic:
from its articulation, the quadrate takes a direction down-
wards and forwards; its inner border sends off a large
pointed ascending process directed upwards, inwards,
and forwards, while its distal end forms a transverse cylin-
droidal articular surface or condyle for the mandible.
61. The columella (Fig. 48), a small and delicate rod
of bone, having its expanded inner end fixed in the fenestra
Fic, 48.—Columba livia. The columella auris (x 8).
The cartilaginous parts are dotted.
est, extra-stapedial ; z.s¢, infra-stapedial: s.s¢, supra-stapedial: s¢,
stapes.
ovalis, a small aperture in the inner wall of the tympanic
cavity, while its cartilaginous outer end is fixed, in the entire
head, to the inner surface of the tympanic membrane (see
§ 317, p. 250.)
The columella consists of a slender bony rod, having at its inner end
an oval plate of bone, the stapes (s7), and at its outer end a tri-radiate
cartilage: the central division of the latter, forming the direct con-
tinuation of the stapedial rod, is the extra-stapedial; the second
division, situated dorsally, is the supra-stapedial (s.s¢); the third,
central in position, the infra-stapedial (z.s¢) ; the supra- is connected
with the extra-stapedial by an oblique bar of cartilage.
62. The pterygoids (Fig. 47, A¢), short, stout, paired
bones on the base of the skull, each articulating behind
02
196 ZOOTOMY.
with a facet on the inner edge of the corresponding quadrate,
and passing inwards and forwards to the rostrum, a small
facet on its inner surface articulating with the basiptery-
goid process (§ 49).
63. The palatines (£/), large paired bones passing for-
wards from the anterior ends of the pterygoids: their poste-
rior ends are scroll-like, their anterior ends slender and free
in the young bird, but ankylosed in the adult with the
maxillz (§ 67).
64. The vomer, a small median bone, lying between the
palatines at the anterior end of the parasphenoid.
65. The lacrymal (/), a considerable bone forming the
anterior wall of each orbit, and articulating above with the
corresponding frontal.
66. The premaxillze (gmx), paired bones forming the
greater part of the beak, and completely ankylosed with one
another in the adult: the anterior or free ends of the united
bones form the strong pointed extremity of the beak, from
which three processes are given off on each side: the first
of these, the nasal process, passes upwards and back-
wards on the dorsal aspect of the beak, fused with its
fellow of the opposite side, to join the anterior edge of the
frontals; the palatine process extends backwards and
slightly outwards on the ventral aspect of the beak, and is
fused in the adult with the corresponding palatine ; and the
maxillary process passes backwards and _ outwards,
external to the palatine process, forming the edge of the
beak, and uniting posteriorly with the maxilla.
67. The maxillee (mx), continuing backwards the max-
illary processes of the premaxillze, to which they are anky-
losed in the adult: anteriorly the inner edge of each is
produced into an inwardly-directed, spongy mass of bone,
the maxillopalatine process (mx), which is ankylosed
THE PIGEON. 197
in the adult to the maxilla: the remainder of the maxilla
forms a very slender rod of bone.
68. The jugal (/z), a slender bone, continued backwards
from the hinder end of the maxilla, with which it is ankylosed
in the adult,
69. The quadrato-jugal, a similar bone to the jugal,
to which it is fused in the adult, and from which it is
continued backwards, its posterior end being attached by
ligament to the outer edge of the quadrate just above its
condyle.
70. The nasal (za), a long, forked bone, fitting against
the anterior edge of the frontal, and having a short external
process (za”) which extends obliquely downwards and for-
wards to the maxilla, and a longer anterior process (za’)
which passes forwards external and parallel to the nasal
process of the premaxilla.
“1, The anterior nasal fosse, large vacuities one on
ach side of the beak, bounded above by the internal pro-
cesses of the nasals and nasal processes of the premaxille,
below by the maxillz, and behind by the external processes
of the nasals.
72. In the fresh state, the mesethmoid (§ 44) is continued forwards to
the end of the beak by a plate of cartilage, the septum nasi, which
forms a median vertical partition between the nasal cavities: it is
produced on each side into scroll-like masses of cartilage, the
turbinals,
IX. In the lower jaw note:
73. The complete fusion, in the adult, of its two halves
or rami in a short median symphysis.
74. The posterior half of each ramus can be separated as
2 distinct bone which fits by a jagged edge into the
corresponding anterior portion: in the young bird, this
proximal portion of the mandible consists of three separate
198 ZOOTOMY.
bones; a stout irregular articular (a7), furnishing the
articular cavity for the quadrate, and continued forwards
into a slender Meckel’s cartilage ; a splint-like bone, the
angular (az), covering the ventral edge of the articular
and Meckel’s cartilage; and the supra-angular (s.an)
similarly related to their upper edge.
75. From the inner face of the distal portion of each
ramus a thin splint, the splenial, can be separated even
in the adult: the remainder of the distal portion is the
dentary (d).
X. Observe in the hyoidean apparatus :
76. The body of the hyoid, consisting of three distinct
portions: the first or glosso-hyal, is cartilaginous and
arrowhead-shaped, the second or basi-hyal, is a short
stout bone, articulating in front with the glosso-hyal, and
behind separated by a cartilaginous interval from the third
portion or basi-branchial, which consists of a slender
bony rod with a free cartilaginous extremity. :
77. The anterior cornua, short, paired, cartilaginous
rods, proceeding backwards and outwards from the posterior
end of the glosso-hyal, like the barbs of the arrowhead.
78. The posterior cornua, slender paired rods, spring-
ing from the cartilaginous junction between the basi-hyal
and basi-branchial, and curving backwards, outwards, and
upwards: each consists, first, of a proximal or ventral
portion, a slender bony rod, the cerato-branchial ; this
is connected at its distal end with a similar rod, the epi-
branchial, which terminates distally in a slender pointed
cartilage.
XI. Make out the characters of the sternum as
follows :
79. The body or corpus sterni, a horizontal boat-
shaped plate of bone, its right and left halves inclined to
THE PIGEON, 199
one another so as to include an obtuse dihedral angle, the
transverse sternal angle.
80. The middle xiphoid process, a narrow, flat,
median plate, forming the hinder. end of the corpus
sterni.
81. The internal xiphoid processes, flat paired
plates proceeding outwards and backwards from the corpus
sterni at the point of origin of the middle xiphoid process,
with the posterior border of which they are connected by
narrow bridges of bone: two large fenestree, covered in the
recent state by membrane, are thus enclosed between the
middle and internal xiphoid processes.
82. The external xiphoid processes, similar to but
much larger than the internal xiphoids, and passing back-
wards and outwards from the lateral borders of the corpus
sterni, about half way between its anterior end and the
origin of the internal xiphoids.
83. The costal border, or that part of the outer edge
of the sternum lying anterior to the external xiphoid process :
it is produced in front into a forwardly directed costal
process, and presents four facets for the articulation of the
sternal ribs.
84. The manubrium or rostrum sterni, asmall blunt
median prolongation of the anterior border of the corpus
sterni.
85. The pneumatic aperture, a small aperture on the
dorsal surface of the corpus sterni about a centimetre behind
its anterior border: through it the interclavicular air-sac
(§ 164, p. 218) communicates with air spaces in the bone,
these spaces can be seen as a delicate transparent network
by holding up the sternum to the light.
86. The coracoid grooves, deep paired fossze on the
anterior border of the body of the sternum, extending
290 ZOOTOMY.
from near the middle line immediately ventral to the
rostrum, outwards and slightly backwards to the costal
processes.
87. The keel or carina sterni, a median ventral plate
of bone, running along the whole middle ventral line of the
corpus sterni from the base of the rostrum to the middle
xiphoid process: its depth is about equal to the breadth of
the body of the sternum.
88. In a bird about three or four weeks old, the sternum is formed of
three distinct bones : one median, the lophosteon, ossifying the central
part of the body and the keel, and an external pair, the pleurostea,
forming the lateral parts.
XII. In the shoulder girdle note:
89. The coracoids, paired rod-like bones, articulating by
their laterally expanded ventral ends with the coracoid grooves
of the sternum, and passing forwards, upwards, and slightly
outwards: each coracoid is somewhat depressed from above
downwards, and presents at its upper end a thickened head:
immediately below the head on the dorsal side of the bone
are two facets for the articulation of the scapula: on the
inner border at about the same level is a facet for the head
of the furcula ($ 91), and on the outer border a large
demi-facet which forms the anterior half of the glenoid
cavity for the articulation of the wing: towards the inner
border of the upper end of the coracoid is a groove passing
into a canal which opens on the upper surface of the head
between the scapular facets, and serves for the passage of the
tendon of the subclavius ($ 326, p. 252): this cavity, being
completed by the articulation of the scapula (§ 90) and the
furcula (§ 91) with the coracoid, is known as the foramen
triosseum.
1 In the young chick a separate pair of ossifications, the metostea,
Gives rise to the internal and external xiphoid processes,
THE PIGEON, 201
go. The scapula, a sabre-shaped bone, articulated
immovably to the corresponding coracoid, so as to make
with it a somewhat acute angle—the coraco-scapular
angle, and passing backwards over the ribs: its proximal
or anterior end is expanded, and presents two facets for
articulation with the coracoid, and, externally, a large demi-
facet which completes the glenoid cavity.
gi. The furcula, or ‘ merrythought,” a V-shaped bone,
articulating by a facet on the outer surface of each of its
extremities with the facet already seen on the corresponding
coracoid, and passing backwards and downwards, its angle
being connected by ligament with the carina sterni.
92. In the young bird, the furcula consists of separate paired bones,
the clavicles, with a small median ossification, the interclavicle,
XIII. Note in the fore-limb :
93. The general composition of the limb: it consists of a
proximal division, the brachium, containing a single bone,
the humerus; a middle division, the antibrachium,
containing two bones, a larger, the ulna, and a smaller, the
radius ; and a distal division, the manus.
94. The position of the parts: in the position of rest the
three divisions are bent upon one another in the form of a
Z ; extended for flight, they are almost in the same straight
line: in the latter case the limb presents a dorsal and a
ventral surface, pre-axial or anterior, and post-axial
or posterior, borders; the radius is then seen to be pre-
axial, and the ulna post-axial. In the position of rest, the
humerus extends backwards from its articulation with the
shoulder girdle, undergoing at the same time a slight
rotation, so that its dorsal surface looks inwards and
upwards, and its pre-axial border outwards and upwards ;
the antibrachium has its dorsal surface directed outward
202 ZOOTOMY.
and its pre-axial border upwards; in the manus the dorsal
surface looks upwards and the pre-axial border downwards
and forwards.
35. The humerus, an elongated bone, consisting of a
cylindrical shaft and of two extremities: the proximal
extremity presents a rounded elevation or head for articula-
tion with the glenoid cavity, a triangular process, the greater
or radial tuberosity on the pre-axial side, and an irregular
elevation, the lesser or ulnar tuberosity on the post-
axial side: on the distal surface of the latter is a deep
excavation leading to the pneumatic foramen which
communicates with a large air-cavity in the shaft of the
bone. The distal end of the humerus has a pulley-like
surface or trochlea, with two raised articular surfaces, one
—the radial tubercle—pre-axial and set obliquely, the
other—the ulnar tubercle—post-axial and nearly at right
angles to the first: just external and proximal to the radial
tubercle is a small roughened elevation, the radial condyle;
the ulnar condyle is similarly related to the ulnar
tubercle.
96. The radius, a straight slender bone, articulating by
its discoid concave proximal extremity or head with the
radial tubercle of the humerus: its distal end bears an oblique,
elongated convexity for articulation with the carpus; it is not
pneumatic.
97. The ulna, a curved bone, having its concave side
towards the radius which it considerably exceeds in thick-
ness: its proximal end presents a concave surface, the
sigmoid cavity, set obliquely to the shaft for articulation
with the humerus, and is produced beyond this facet, post-
axially, into a short, blunt process, the olecranon 3 a short
process is also given off from the dorsal and pre-axial region
which partly embraces the head of the radius,
THE PIGEON. 203
98. The carpus, or proximal division of the manus, con-
sisting of two short bones, the smaller (radiale, Fig. 49,
cp.1) articulating with the radius, the larger (ulnare, ¢f.2)
with the ulna.
99. The metacarpus or middle division of the manus,
consisting of (a) a large cylindrical bone, the second meta-
carpal (mcf.2); (2) a slender curved bone, the third
metacarpal (c.3), on the post-axial side of the second,
to which it is ankylosed at its extremities, its shaft remaining
Fic. 49.—Columba livia. The left manus of a nestling (about four-
teen days old), viewed from the outer (dorsal) surface (x 2).
The cartilaginous parts are dotted.
cp.t, radial, and ¢f.2, ulnar carpal: mcp.1, first, mcp.2, second, and
mcp.3, third, metacarpal: ~/.1, phalanx of pollex: £4.2, proximal, and
ph.2’, distal phalanx of second digit : #%.3, phalanx of third digit : ra,
radius : 2#/, ulna.
free; (c) the first metacarpal (mc.1), forming merely a
projecting process on the pre-axial border of the proximal
end of the second.
100. The phalanges, forming the distal division of
the manus: one pointed bone (4.1), attached to the
204 ZOOTOMY.
rudimentary first metacarpal is the single phalanx of the first
digit or pollex: the second digit has two phalanges, the
proximal one (/.2) being flattened and very thin on its
post-axial side, the distal one (f/.2’) pointed and concave
dorsally: the third metacarpal bears a single pointed
phalanx (f/.3).
tor. In the young bird the metacarpals are distinct bones
with cartilaginous epiphyses.
XIV. Make out the characters of the pelvis or hip
girdle as follows :
toz, It consists of two paired bones, the ossa inno-
minata (Fig. 50), more or less extensively ankylosed to
aw
aly ul
Fic. 50.—Columba livia. Left os innominatum of a nestling
(fourteen days), viewed from without (x 2).
The cartilage is distinguished by dotting.
ac, acetabulum: a.¢r, anti-trochanter: 7, pre-, and zi’, post-
acetabular portion of ilium: zs, ischium: 7.5.f, ilio-sciatic foramen :
ob.f, obturator fissure : fz, pubis.
the sacrum in the adult, but easily separable in the young
bird.
103. The acetabulum (Fig. 48, ac), a rounded articular
cavity on the outer surface of each os innominatum, per-
forated by an aperture, and serving for the articulation of the
leg: its postero-dorsal region is prolonged into a distinct
facet, the anti-trochanter (a./r).
THE PIGEON. 208
104. The ilio-sciatic foramen (7.s,/), a large aperture
immediately posterior to the acetabulum.
ro5. The pubis (fz), a slender’ bony rod, forming the
ventral part of the acetabulum and the ventral border of
the post-acetabular portion of the innominate bone: it is
separated from the rest of the bone by a long cleft, the
obturator fissure (02./).
106. The ischium (7s), consisting of that part of the
post-acetabular portion of the innominate bone which lies
above the obturator fissure and below and behind the ilio-
sciatic foramen : at the acetabulum it is ankylosed with the
anterior end of the pubis.
107. The rest of the os innominatum is formed by the
ilium (7, 7/’), which consists of pre- and fost-acetabular
portions, the former (7/) ankylosed at the ventral boundary
of the acetabulum with the pubis, the latter (2?’) ankylosed
with the ischium in the postero-dorsal region of the
acetabulum, as well as behind the ilio-sciatic foramen.
108. In the young bird the os innominatum consists of
a distinct mass of cartilage of the same shape as the adult
bone, in which the ilium, ischium, and pubis are formed.
as separate ossifications, which unite with one another at a
later period.
XV. In the leg make out:
109. Its general composition : it consists of a proximal
division, containing a single bone, the femur; a middle
division, the crus or shank, containing a large bone, the
tibio-tarsus, and a small and imperfect one, the fibula;
and a distal division, the pes, formed of a cylindrical
bone, the tarso-metatarsus, to which four digits are
attached.
110. The position of the parts: the femur is directed
downwards and forwards from its articulation with the
206 ZOOTOMY.
pelvis ; the crus is directed downwards and slightly back-
wards, the tarso-metatarsus downwards and slightly forwards,
three of the digits are directed forwards and rest with their
whole lower surface on the ground, while the remaining toe
—the hallux or first digit—is directed backwards, and
slightly raised from the ground at its proximal end.
11x. If the leg is extended outwards at right angles to the
body it is seen to present, like the fore-limb, dorsal and
vental surfaces and pre-axial and post-axial borders: in the
natural position of the parts the pre-axial border is internal
throughout: the whole limb ; the primitively dorsal surface
looks upwards and forwards in the femur, forwards and
slightly downwards in the crus, forwards and slightly upwards
in the tarso-metatarsus, and upwards in the digits.
112, The femur, a cylindrical bone consisting of shaft
and extremities: the proximal extremity is produced on
the pre-axial (inner) side into a rounded elevation or head,
the axis of which is at right angles to that of the shaft, and
which serves for articulation with the acetabulum: post-
axially is a large irregular elevation, the great trochanter,
and between it and the head on the actual proximal end of
the bone is a facet which works against the anti-trochanter
(§ 103). The distal end of the femur is pulley-like, and
formed of two condyles; of these the outer or post-
axial condyle is deeply grooved in its ventral region, thus
furnishing the fibular fossa for the articulation of the
fibula; the rest of the outer and the whole of the inner
condyle articulates with the tibio-tarsus.
113. The tibio-tarsus, a cylindrical bone about half as
long again as the femur: its shaft, together with the proximal
extremity, corresponds to the tibia ; its distal extremity re-
presents the proximal portion of the tarsus, and therefore
really belongs to the pes. The proximal extremity bears
THE PIGEON, 207
two slightly concave articular surfaces for the condyles of the
femur, and is produced in front (dorsally) into a prominent
cnemial crest divided into two diverging plates. The
distal extremity is pulley-shaped, and its transverse axis is
inclined at an angle to that of the proximal extremity: the
two condyles of which the distal pulley is formed are
more prominent on the anterior (dorsal) than on the
posterior face of the bone, thus differing from the very
similar condyles of the femur.
Fic, 51.—Columba livia. Left tarso-metatarsus of an unhatched
embryo, with the distal end of the tibio-tarsus, viewed from the
anterior (dorsal) face (x 5).
The tarsal cartilages (¢/.1, #.2) are represented as separated from
the tibia and metatarsus respectively.
The cartilaginous parts are dotted.
mtl,2, second, mtl.3, third, and wzt/.4, fourth metatarsal: zz, tibia :
#7.1, proximal tarsal cartilage, afterwards fusing with tibia: ¢/.2, distal
tarsal cartilage, afterwards fusing with metatarsus.
114. In a pigeon embryo towards the end of incubation,
the distal end of the tibio-tarsus is a separate cartilage, the
proximal tarsal cartilage (Fig. 51, ¢/.1) : its separateness
in the cartilaginous state distinguishes it from an epiphysis,
which is a distinct ossification in a continuous cartilage.
208 ZOOTOMY.
115. The patella, a small nodule of bone in front of
the knee-joint, connected by ligament with the femur and
tibio-tarsus.
116. The fibula, aslender bony rod attached to the outer
(post-axial) side of the tibio-tarsus: its proximal end articu-
lates with the fibular fossa in the outer condyle of the femur:
distally it undergoes a gradual diminution in diameter and
finally fuses with the tibio-tarsus.
117. The tarso-metarsus, a cylindrical bone articulated
to the distal end of the tibio-tarsus, its proximal end bearing
two concave surfaces for the condyles of the latter bone:
behind (ventrally) it is produced at its proximal end into a
strong crest, on either side of which is a small foramen
passing through to the somewhat concave anterior face of
the bone: its distal end is trifurcate, the middle division
being the longest, and each bearing a pulley-like surface
for the articulation of one of the toes. That part of the
tarso-metatarsus which lies above (proximal to) the two
foramina represents the distal tarsals : in the remainder of
the bone, the two foramina and trifurcate distal ends indicate
a division into three longitudinal parts, the second, third,
and fourth metatarsals. The joint between the tibio-
tarsus and tarso-metatarsus is conveniently known as the
mesotarsal articulation, being between the proximal
and distal tarsals.
118. In an embryo towards the end of incubation, the
proximal extremity of the future tarso-metatarsus is a
separate cartilage, the distal tarsal cartilage (Fig. 51,
#.2) and the remainder is formed of three separate long
bones, (metatarsals, m7z/.2, md/.3, m#l.4), in close contact save
at their distal ends.
119. The hallux, or first pre-axial digit, consisting of a
separate metatarsal, united by ligament to the inner border
THE PIGEON, 209
of the tarso-metatarsus near its distal end, and of two
phalanges, a proximal and a distal, the latter modified for
the support of a claw.
120, The three forwardly directed toes, representing the
second, third, and fourth digits, and having their metatarsals
united to form the tarso-metatarsus: the second digit, or
irinermost of the three, consists of three phalanges, the next
of four, and the fourth or outermost of five, the distal pha-
lanx in each case being modified for the support of
a claw.
B.—DIRECTIONS FOR DISSECTION,
XVI. Either pluck the feathers from one side of
the bird, leaving the other side untouched, or
better, have two birds for comparison, one entire,
the other plucked: note the following external
characters :
r2t. The division of the body into head, neck, trunk,
and limbs: the relatively great length of the neck: the
absence of a true tail, the body terminating posteriorly
in a short obtusely conical process, the rump or
uropygium.
122. The great influence of the external covering of
contour feathers or penne in determining the contour
of the body, the form of the plucked bird being altogether
different from that of the entire one.
123. The filoplumes, small, hair-like feathers, situated
between the contour feathers, and exposed by the removal
of the latter in the plucked bird.
124. The rounded form of the cranial portion of the
head, and the production of the facial portion into a
P
210 ZOOTOMY.
beak, devoid of feathers but covered with a strong, horny
sheath, except at the base, where there is on each side a
tumid naked area of skin, the cere.
128. The mouth, bounded above and below by the
upper and lower divisions of the beak (upper and lower
mandibles of ornithologists).
126. The nostrils, or external nares, oblique, slit-
like, paired apertures immediately in front of the cere.
127. The eyes, situated a little posterior to the angle of
the mouth: each is provided with an upper and a lower
eyelid, both devoid of feathers, and with a nictitating
membrane, which is easily found in the anterior angle
of the eye, and can be pulled backwards over the eye as a
whitish, semi-transparent membrane.
128. The auditory aperture, situated a short distance
below and behind the eye, of a rounded form, and lead-
ing into a canal, the external auditory meatus: in the
entire bird the auditory aperture is quite concealed by the
feathers.
129. The flaccid condition of the skin about the neck,
due to the more or less empty condition of the crop
(§ 150).
130. The breast of the bird, formed by the muscles
covering the sternum: the keel of the latter (§ 87) can be
felt as a median bony ridge extending from a short distance
behind the root of the neck to within 11 inches of the
posterior extremity of the body.
131. The soft, ventral, abdominal walls behind the
posterior edge of the sternum, bounded externally and
posteriorly by the pubes (§ 105).
132. The vent, or cloacal aperture, a considerable
transverse cleft with tumid lips, situated on the ventral
surface of the hinder end of the trunk.
THE PIGEON. 2i1
133. On the dorsal surface of the conical posterior extremity of the
trunk is a small papilla on the apex of which opens the duct of the
uropygial or oil-gland (§ 296, p. 247).
134. The division of the fore-limb or wing into a
proximal portion, the brachium or upper arm, a middle
portion, the antibrachium or fore-arm, and a distal portion,
the manus or hand, the three divisions being bent upon
one another when at rest in the form of a Z: the absence of
distinct digits, except in the case of the pollex or thumb,
which forms a small projection on the pre-axial (§ 94) border
of the manus at its proximal end.
135. The alar membrane, a fold of skin, extending
between the proximal end of the fore-arm and that of the
hand on the pre-axial side.
136. The division of the hind-limb into a proximal
portion, the thigh or femur, a middle portion, the shank or
crus, and a distal division, the foot or pes; the latter
consists of a proximai stem, the tarso-metatarsus, and of
four digits, the first (pre-axial, § 111) of which is directed
backwards, and all of which terminate in strong claws.
137. The arrangement of the feathers on the neck and
trunk: they are not continuous, but forma number of
feather-tracts or pteryle, separated by featherless
spaces or apteria: the former being indicated in the
plucked bird by the scars left by the removal of the
feathers.1 Along the dorsal surface runs the spinal tract,
the cervical portion of which is particularly well marked,
1 The pterylosis, or feather arrangement, is better made out in the
sparrow than in the pigeon, as in the latter the feather tracts tend
to run together: in the sparrow, on the contrary, the spinal tract is
almost linear, broadening out only in the lumbar region; the ventral
tract consists of two very narrow bands separated by an inferior space
occupying nearly the whole of the pectoral region ; the lateral spaces are
also very large.
P 2
212 ZOOTOMY.
and bifurcated posteriorly: on the ventral surface is the
ventral tract, divided in the region of the trunk into two
lateral portions separated from one another by the median
inferior space: throughout the greater part of its extent
the ventral is separated from the spinal tract by the lateral
spaces, one on either side of the trunk and neck.
138. The arrangement of the tail feathers : attached along
the posterior edge of the rump are twelve large rectrices
or tail quills, the position of which is indicated by well
marked scars in the plucked bird: the proximal ends of the
rectrices are covered both above and below by smaller
feathers, the tail coverts, attached to the upper and under
surface of the rump.
139. The arrangement of the feathers on the wing: along
the post-axial edge of the antibrachium and manus is
attached a row of about twenty large remiges or wing
quills, of which those attached to the manus are the
primaries, those attached to the antibrachium the
secondaries: their position is clearly indicated in the
plucked bird by large scars. Both on the upper and under
surface of the wing the remiges are largely covered by the
upper and under wing coverts, which also form the entire
feathery covering of the upper arm: on the dorsal surface of
the latter the feathers are arranged in a well marked
humeral tract; the secondary upper wing coverts spring
from an alar tract. A special tuft of feathers springs
from the pollex, and constitutes the ala spuria or bastard
wing.
140. The arrangement of the feathers on the leg: there is
a well defined femoral tract on the dorsal surface of the
thigh, and a weak crural tract on the shank.
141. The absence of feathers on the pes, which is covered
instead by horny scales: these are especially large on the
~
aa
THE PIGEON. 213
anterior (dorsal) surface of the tarso-metatarsus and on the
dorsal surface of the toes,
XVII! In one of the large quill feathers make out the
following points:
142, The stem, or scapus, consisting of a proximal
portion, the tube or calamus, which is cylindrical and
hollow or nearly so, and of a distal portion, the shaft or
rachis, which is somewhat quadrate in section, grooved on
its ventral? side, and formed internally of a white, pith-like
substance.
143. The barbs, delicate tapering processes, flattened in
a direction at right angles to the long axis of the feather and
attached in two rows one on each side of the rachis: they
constitute, taken together, the vane or vexillum of the
feather.
144. The inferior umbilicus, a small aperture at the
proximal end of the calamus, by which the feather-papilla
enters the latter.
145. The superior umbilicus, a small oblique aperture
at the junction of the calamus and rachis, putting the
cavity of the former in communication with the exterior.
XVIII. Cut off a small piece of the vane and examine it under a
moderately high power of the microscope, taking care to
distinguish between the dorsal and ventral surfaces, and the
proximal and distal ends of the piece. It is advisable to soak
the fragment for a short time in alcohol, so as to remove the
air, and then to examine in glycerine, Note:
146, The barbules, small pointed processes, attached obliquely in two
rows one on each side of the barbs, to which they are related in the
same way as are the latter to the rachis: they are so disposed that the
1 It will probably be found convenient, in practice, to omit Sections
XVII—XIX until the dissection of the soft parts is completed, and to
proceed from § 141 to Section XX., p. 214. ;
2 That is, the lower side in the case of the remiges and rectrices, or
the inner side in the case of the ordinary contour feathers.
214 ZOOTOMY,
distal barbules of any given barb overlap and cross at an angle the
proximal barbules of the barb next in advance,
147. The hooklets, minute curved processes on the distal barbules,
by means of which the latter are hooked on to the proximal barbules of
the next succeeding barb: the proximal barbules themselves are devoid
of hooklets.
XIX. Pluck out a filoplume and examine it in the same way:
note :—
148. The delicate stem, showing no distinction between calamus
and rachis.
149. The rudimentary vane, consisting of a few barbs with simple
disunited barbules.
XX. In the plucked bird, thrust a blowpipe into the
mouth and loop a string round the base of the
beak immediately behind the cere, tightening it
just enough to hold the blowpipe in place and
prevent the escape of air: inflate until the neck
and abdomen are greatly swelled owing to the
distension of the crop (§ 150) and the air-sacs
($ 159): withdraw the blowpipe, at the same time
tightening the ligature: then knot the latter to
prevent its loosening.
By this method both crop and air-sacs are inflated
simultaneously without injury to any of the
structures to be afterwards examined: if in the
course of dissection one or other should collapse
—which is certain to happen sooner or later—cut
across the trachea ($ 151) and inflate the crop from
its anterior and the air-sacs from its posterior end,
ligaturing as before.!
1 Ifit is desired to make a careful dissection of the air-sacs, dissect
away the muscles from the humerus, and cut that bone across a short
distance from its distal end: slip over the cut end a piece of indiarubber
tubing, to the other end of which is fixed a short glass tube: fix the
latter in a vertical position: make an incision into the trachea and
insert a cannula directed backwards, tying it securely : inject slowly with
THE PIGEON. 215
Make a longitudinal incision through the skin over the
keel of the sternum, and continue the incision
backwards to the vent and forwards to the throat :
dissect away the skin from the whole ventral
surface of the body and reflect it right and left,
being especially careful in removing it from the
crop, to which it is closely adherent. Note :—
150. The cesophagus or gullet, a wide thin-walled
tube, lying along the ventral aspect of the neck, and
enlarging posteriorly into a bilobed dilatation, the crop:
both gullet and crop are now unnaturally distended.
rs1. The trachea, a narrow tube, surrounded’ at short
intervals with bony rings, which give it an annulated
appearance: it lies on the ventral side of the anterior end of
the gullet, but soon crosses to the left and passes to the
dorsal side of the crop.
152. The jugular veins, large vessels, usually gorged
with blood in a freshly killed bird, running one on each side
of the neck, dorsal to the crop: each jugular is seen to
receive feeders from the gullet and crop, as well as from a
more or less extensive venous plexus in the skin of
the neck.
153. The pecteralis major, a large muscle forming
the greater part of each side of the breast: its fibres are
readily seen to arise from the carina sterni and from the
clavicle, and to pass forwards and outwards, converging
as they go, to the ventral aspect of the humerus (see
§ 327, P. 252).
154. The abdominal muscles, forming the soft fleshy
plaster of Paris or gelatine (see p. 48, § 162) until the injecting fluid rises
in the glass tube. When the plaster or gelatine has set, remove the india-
rubber tube from the humerus, and proceed as directed in the succeeding
paragraphs,
216 ZOOTOMY.
ventral walls of the body between the posterior edge of the
sternum and the pubes.
155. The rectus abdominis, a narrow paired muscle formed of
longitudinal fibres, forming with its fellow the median portion of the
ventral abdominal wall: it extends from the posterior border of the
sternum to the pubis ; its posterior portion is tendinous.
156. The obliquus externus, a broad sheet of muscle forming the
lateral portion of the abdominal wall, and extending, in front, over the
posterior ribs: the muscle proper, consisting of fibres directed down-
wards and backwards, only extends about half way between the
posterior border of the sternum and the pubis, but is continued back-
wards to the latter bone by a strong sheet of connective tissue or
aponeurosis,
157. The obliquus internus, situated beneath the external oblique,
which must be removed to show it: it is almost co-extensive with the
external oblique, and like it, its posterior portion is aponeurotic : its
fibres are nearly longitudinal in direction.
158. Thetransversus abdominis, lying beneath the internal oblique
and formed of transversely directed fibres, which are seen through the
posterior or aponeurotic portions of the obliqui.
XXI. Make a median longitudinal incision through
the abdominal walls from the posterior edge of
the sternum to the vent: from the anterior end of
this cut make transverse incisions along the
posterior border of the sternum, taking care not
to cut too deeply and so injure the air-sacs
(§ 159): carefully reflect the flaps of muscle thus
separated, and note:
159. The (abdominal) posterior air-sacs, one on
either side of the body-cavity or ccelome now exposed :
they are transparent thin-walled sacs, unnaturally distended
with air, and largely concealed at present by the great
omentum (§ 161) and the viscera (§ 162).
160. The posterior-intermediate air-sacs, lying one
on each side immediately in front of the corresponding
THE PIGEON, 217
abdominal sacs: to see them the edge of the sternum must
be slightly raised.
161. The great omentum, a sheet of membrane,
loaded with fat, which covers the contents of the abdomen ;
by carefully lifting it the posterior air-sacs will be better
displayed.
162. Some of the abdominal viscera (liver, intestine,
&c.) can also be seen at this stage of the dissection, but are
best examined later (§ 171, &c.).
XXII. Carefully dissect away the crop from the
anterior surface of the sternum and_ pectoral
muscles, taking care not to injure the inter-
clavicular and prebronchial air-sacs (§ 164) : make
a longitudinal incision through either of the great
pectoral muscles close to the carina sterni,—the
incision should be about half an inch deep at the
anterior end of the carina, gradually diminishing
in depth as it is continued backwards, and must
be made with considerable care, so as not to
injure the subclavius muscle (§ 166): continue
the incision forwards, gradually separating. the
pectoralis major from the furcula, and from the
posterior end of the incision continue it outwards
so as to separate the muscle from the corpus
sterni: when these attachments, together constitut-
ing the origin of the pectoralis, are cut through,
the muscle will come away quite easily from the
underlying parts: reflect it outwards, taking care
not to injure the pectoral vessels ($ 168) or the
axillary air-sacs (§ 165), and note:
163. The distal portion of the gullet, passing backwards
from the crop, of which it looks like a middle lobe, to reach
the body-cavity.
218 ZOOTOMY.
164. The interclavicular air-sac, situated at the
bottom of the pit bounded at the sides by the furcula and
pectoral muscles, in front by the crop and by the carina:
it is distinctly bilobed, being formed by the fusion of two
sub-bronchial air-sacs, and extending on either side of
the gullet: immediately dorsal to each of its lobes is one of
the paired prebronchial air-sacs.
165. A prolongation of the interclavicular air-sac on each
side into the corresponding axilla, placed just external
to the coracoid, and covered immediately by the pectoralis
major.
166. The subclavius or pectoralis secundus, a
broad flat sheet of muscle, arising from the dorsal portions
of the keel and median portions of the body of the sternum:
it is a bi-pinnate muscle, that is, is divided longi-
tudinally by a tendinous band to which the fibres of either
side converge: anteriorly it is seen to pass forwards and
outwards between the furcula and the axillary prolongation
of the interclavicular air-sac.
167. The coraco-brachialis longus, a small muscle
lying external to the anterior portion of the subclavius, and
passing forwards and outwards dorsal to (beneath in the
present position) the axillary portion of the interclavicular
air-sac.
168. The pectoral arteries and veins, large vessels
distributed to the pectoral muscles, and, at present, pre-
venting further reflection of the pectoralis major.!
1 The injection of the pigeon’s vascular system is best performed in
the following way. As soon as the bird, killed with chloroform or
potassic cyanide, is dead, pluck the breast, expose the pectoral vessels of
one side as directed in Section XN NII., cut through these vessels as near as
possible to the reflected pectoralis major, and allow to bleed. All this
should be done with the greatest rapidity, as birds’ blood coagulates
very quickly, and it is essential to success to allow as much as possible
THE PIGEON, 219
XXIII. Ligature the pectoral vessels, if the subject is
not injected: cut through the origin of the sub-
clavius and reflect it: cut away the greater part of
both pectoralis and subclavius, leaving a recognis-
able portion of the anterior end of each still
attached to the upper arm: do the same on the
other side,,thus exposing the whole sternum as
well as the greater part of the coracoids and
furcula: make a longitudinal cut, with strong
scissors, through one side of the sternum parallel
and close to the keel, and extending to about the
middle of the latter: gradually cut or break away
the posterior part of the body of the sternum
external to this incision until the following
structures can be seen:
169. The anterior-intermediate air-sac, immediately
in front of the corresponding posterior-intermediate (§ 160).
170. The falciform ligament, a median vertical sheet
of peritoneum, attached along the middle line of the sternum,
and passing dorsalwards among the viscera (§ 185).
to escape. Remove the corpus sterni on the same side, so as to expose
the heart and see the origin of the pectoral vessels (§ 168): insert a
cannula into the pectoral artery through the incision already made, tie
securely, and inject towards the heart: in this way the whole of the
arterial system is filled. The systemic veins may be injected from the
pectoral vein, but better results are obtained by injecting from the
coccygeo-mesenteric vein (§ 197), the cannula being injected backwards,
or towards the renal portal veins : the severed pectoral vein should first
be tied or clamped with bull-dog forceps. It will probably be found
necessary to inject the precavals (§§ 243, 245) and their feeders separately :
this is best done by making an incision in one of the jugulars (preferably
that of the side on which the pectorals have already been cut) near its
proximal end, and injecting forwards. The portal system is best
injected from the coccygeo-mesenteric vein (§-197), the cannula being
directed forwards,
220 ZOOTOMY.
In the uninjured state the falciform ligament is continued backwards
attached to the middle ventral line of the abdomen.
XXIV. Cut through the other side of the sternum in
the same way: lift up the keel, and gradually
extend both incisions forwards, using bone-forceps
when necessary, until the whole of the central part
of the sternum is removed: cut through each
coracoid at about its middle and remove its
ventral portion: also remove the furcula, and
enough of the lateral regions of the sternum, with
the sternal ribs, to bring all the viscera into view:
note, without disturbing anything :
171. The reddish-brown liver, occupying the middle
region of the ccelome, and consisting of a large right and a
small left lobe.
172. The heart, very large in proportion to the size of
the animal, lying in the middle line in front of the liver, and
enclosed in a thin membrane, the pericardium.
173. The duodenum, a pinkish, U-shaped loop of
intestine, passing from beneath the edge of the right lobe
of the liver to the posterior end of the ccelome, and
consisting of a left or proximal and a right or distal limb.
174. The pancreas, a compact reddish gland, lying
between the two limbs of the duodenal loop.
175. One or two loops of the ileum (the chief part
of the small intestine) are seen towards the right of the
ccelome.
176. The gizzard, a hard oval body, on the left
side of the body, just posterior to and partly concealed by
the liver.
177. The distal end of the trachea, curving round the
left side of the crop to reach the ventral aspect of the
gullet, and almost immediately dividing into the two
THE PIGEON. 221
bronchi, which pass outwards and backwards to the lungs
(§ 181).
178. The cavity in which the posterior end of the trachea
and the bronchi lie is the interclavicular air-sac (§ 164),
the ventral wall of which is destroyed by the removal of the
sternum,
179. The sterno-tracheal muscles, paired slender
bands, easily mistaken for arteries, passing from the ventral
side of the trachea outwards and backwards to the inner
surface of the sternum.
180. The epigastric or anterior abdominal vein, a
small vessel, taking blood from the great omentum, and
passing forwards in the falciform ligament towards the
anterior border of the liver (see § 253, p. 240).
181, The lungs, dark-red, spongy bodies, seen by turn-
ing aside the heart: they are closely applied to the dorsal
wall of the anterior part of the ccelome.
182. The kidneys (§ 214) and the reproductive
organs (§§ 209—213), seen by turning aside the intestines
in the dorsal region of the posterior part of the ccelome.
XXV. Make a median incision through the skin on the
dorsal surface of the head, and reflect it to right or
left, so as to expose the skull: beginning a little
behind the eyes, cut away the thin cranial roof
with a scalpel or pocket-knife, taking great care
not to injure the brain, which is in close contact
with the bone (consult Fig. 58, p. 255): proceed
until the whole of the roof of the skull and the
arches of the first two or three vertel re are
removed: when the whole of the dorsal and
lateral surfaces of the brain are clear, cut through
the spinal cord a short distance behind the
brain: lever up the front of the brain with the
ZOOTOMY.
h
iS)
w
handle of a small scalpel, and cut through, one by
one, the nerves which pass from its lower surface;
remove the whole organ and place it in strong
alcohol or in a saturated solution of zinc chloride
for subsequent examination (see § LV., p. 254).
XXVI. If time permit, continue backwards the incision
through the skin, and cut away the arches of all
the remaining vertebrae so as to expose the whole
spinal cord: in any case, remove the skin from
the middle region of the back just between the
thighs, and cut away the arches of the middle
sacral vertebrae, so as to expose about an inch of
the cord in that region: note : ,
183. The lumbar enlargement of the cord, and the
divergence ofits dorsal columns, which enclose a diamond-
shaped depression, the sinus rhomboidalis, produced
by the widening of the central canal of the cord, and
covered only by its investing membrane or pia mater.
184. If the whole cord is exposed, the brachial enlargement will
be seen between the shoulders as well as the very great proportional
length of the cervical region of the cord.
XVII. Place the subject once more in the supine
position (ventral surface uppermost), and make
out the following points by merely turning the
viscera about, and without cutting or tearing
anything:
185. The relations of the falciform ligament (§ 170):
in front it becomes attached to the pericardium: at its
dorsal edge the two layers of which it is composed diverge,
forming two lamine, of which the right passes across the
duodenum and becomes attached to the posterior surface of
the right lobe of the liver, forming the duod- no-hepatic
omentum, while the left becomes attached to the peri-
THE PIGEON, 223
toneal investment of the gizzard : both layers are continued
backwards as the great omentum (§ 161).
186. The characters of the liver: its division into a
large right and a small left lobe: its free backwardly directed
ventral border: its anterior surface, hollowed out for the
reception of the heart : its posterior surface, hollowed by two
grooves on the right lobe for the duodenum, and by a deep
fossa on the left lobe for the gizzard.
187. The gastro-hepatic omentum, a sheet of
peritoneum connecting the gizzard with the left lobe of
the liver.
188. The mesogaster, a sheet of peritoneum connecting
the gizzard with the dorsal body wall.
189. The mesentery, a greatly folded sheet of peritoneum
supporting the coils of the intestine, and connecting them
with the dorsal body wall.
190. The posterior portion of the intestine, passing along
the middle line of the dorsal body wall towards the vent,
and suspended by a sheet of peritoneum, the meso-
rectum : about an inch in front of the vent are two small
lateral elevations, the czeca, on the walls of the gut,
marking the distinction between the small intestine
in front of them, and the large intestine or rectum
behind.
191. The cloaca, a somewhat dilated chamber, open-
ing externally by the vent, and connected in front with
the rectum : its form and relations are best seen by inflating
with air from the vent.
XXVIII. Dissect away the great omentum, turn for-
ward the lobes of the liver and dissect out the
following structures :
192. The right bile duct, a delicate, whitish tube,
proceeding from the posterior surface’ of the right lobe
224 ZOOTOMY.
of the liver, near its dorsal margin, and passing backwards,
in the duodeno-hepatic omentum, to open into the distal
limb of the duodenum, at about the junction of its middle
and distal (anterior) thirds.
193. The left bile duct, a much wider and shorter tube
than the right; also arising from the right lobe of the liver,
and passing backwards to open into the proximal limb of
the duodenum, about half an inch beyond the pylorus
(see §§ 204, 207).
194. The portal vein, a large vessel, usually gorged
with blood, lying in the duodeno-hepatic omentum between
the two bile ducts ; it receives blood from the intestines and
spleen, and from the right side of the gizzard, and divides
into two branches, one of which enters each lobe of the
liver.
The portal vein is formed by the union of three chief veins: the
gastro-duodenal, receiving blood from the right side of the gizzard, the
duodenum, and the last loop of the small intestine (§§ 173-176); the
superior mesenteric, from the main part of the small intestine
(jejunum and ileum, § 204) ; and the inferior mesenteric or coccygeo-
mesenteric (§ 197), from the posterior portion of the small intestine,
the rectum, and the cloaca, ©
195. The three pancreatic ducts: of these one leaves
the right side of the anterior end of the pancreas, and
passes forwards and to the right, to enter the intestine
a short distance beyond the termination of the distal
limb of the duodenum ; the other two usually spring from
about the middle of the gland, also from its right border,
and pass slightly forwards, more or less parallel with one
another, to enter the duodenum at about the middle of its
distal limb.
196. The left gastric veins, two small vessels con-
tained in the gastro-hepatic omentum, and carrying the
THE PIGEON. 225
blood from the left side and anterior edge of the gizzard
to the left lobe of the liver.
197. The coccygeo-mesenteric or inferior mesen-
teric vein (Fig. 54, ¢.v), a large trunk, running in the
mesorectum, parallel to the intestine, and receiving veins
from the cloaca and rectum: it anastomoses at its dorsal
or posterior end with the renal portal veins (see § 218),
and at its anterior end joins the portal vein (§ 194).
XXIX. Tie a double ligature round the portal vein
(the bile ducts may be included), and cut it
between the ligatures : if the specimen is injected,
the vein may be cut without tying : cut through the
gastro-hepatic omentum, and turn the liver over to
the right : note:
198. The proventriculus, a pink, ovoidal body with
thick glandular walls, lying immediately in front of the
gizzard (see § 204), and to the dorsal side of the heart and
liver.
199. The spleen, a small, ovoidal, red body, attached
to the right side of the proventriculus by a fold of
peritoneum, the gastro-splenic omentum.
200. The coeliac artery, seen emerging from between
the right lobe of the liver and the proventriculus ; its. origin
from the dorsal aorta is best observed later (§ 228): it
supplies the proventriculus, gizzard, liver, and part of the
intestine.
The cceliac divides into two chief trunks: one, the anterior gastric,
sends small branches forward to the proventriculus, and then proceeds
to the left side of the gizzard ; the other, the gastro-duodenal, supplies
the right side of the gizzard, the duodenum, and the last loop of the
ileum.
201. The gastric branch of the vagus, a delicate nerve on the
anterior face of the proventriculus, parallel to its artery, and passing
backwards to the gizzard.
Q
226 ZOOTOMY.
202. The splanchnic nerve, running parallel to the gastro-duodenal
artery, and supplying the intestine.
203. The anterior (superior) mesenteric artery,
about a quarter of an inch posterior to the cceliac, and
supplying the greater part of the intestine: to bring it into
view the duodenum must be pulled outwards by dissecting
away part of its peritoneal investment.
XXX. Tie a double ligature round the intestine a little
anterior to the caeca, including in the ligature the
coccygeo-mesenteric vein: cut through the pro-
ventriculus as far forwards as possible without
injury to the heart, &c.: remove the alimentary
canal between these two points by cutting the
mesentery, noting a fibrous membrane (the oblique
septum) connected with the dorsal and anterior
face of the pericardium in front, and extending
across the ccelome like the roof of a tent: it is
attached to the margins of the sternum in front,
and to the body walls behind, in such a manner
as to separate a sub-puimonary chamber,
containing the air-sacs, from the general body
cavity. Then observe:
204, The arrangement of the different parts of the
alimentary canal: the proventriculus enters the gizzard on
its anterior edge : the duodenum leavesit at the anterior end
of its right side: following the duodenum is ‘a distinct
single loop of small intestine, the jejunum, and after
this a coil, consisting of the greater part of the ileum,
bound together by a single fold of mesentery: next comes
the distal portion of the ileum, consisting of a single loop,
of less calibre than the remainder, and usually of a greenish
colour: leaving the distal limb of this loop, the ileum widens
again, and passes without increase of diameter into the rectum.
THE PIGEON. 227
205. The strong, hard walls of the gizzard: the bluish
tendons, occupying the central portion of its convex right
and left sides, and the muscular fibres radiating from the
circumference of each tendon to the edge of the organ,
XI. Unravel the intestine by cutting or tearing
through the mesentery, and measure_its length as
compared with that of the ccelome: then cut
open the proventriculus and gizzard, the latter by
a vertical incision inidway between its two convex
faces: also cut open portions of the intestine, and
observe :
206, The thick glandular walls of the proventriculus,
presenting on their inner surface the well-marked apertures
of the gastric glands.
207. The very thick muscular walls of the gizzard, and
its lining of thick, horny, yellow or green epithelium:
the small stones with which its cavity is largely filled: the
place of entrance of the proventriculus, a wide aperture at
its anterior end, and the pylorus, or place of exit of the
intestine, a crescentic aperture to the right of the former
opening.
208. The villi, minute filamentous processes of the
mucous membrane of the small intestine : seen to advantage
only by examining under water, after well cleaning: in
the duodenum and proximal portion of the ileum they
are comparatively long and closely set, but in the distal
portion of the ileum they become shorter and sparser, and
towards the end of that division of the intestine pass into
longitudinal ridges.
XXXII. Dissect away the peritoneum and the re-
mains of the posterior air-gacs from the kidneys
and reproductive organs, taking care not to
injure the postcaval vein (§ 215), and, in the
Q 2
228 ZOOTOMY.
female, the anterior end of the oviduct (§ 212):
make out :
Ln the mate.
209. The testes (Fig. 52, 4s), two white, ovoidal bodies,
about three-quarters of an inch long in the adult, but very
Fic. 52.—Columba livia. ‘The urinogenital organs of an adult
male, ventral aspect (x 3).
The right testis and vas deferens are separated from the kidney and
ureter, and displaced outwards.
adr, adrenal: c/.2, middle, and ¢/,3, posterior, compartment of cloaca :
&, kidney: ¢s, testis: wz, ureter: uw’, opening of ureter into cloaca:
v.d, vas deferens : v.a’, its openitig into cloaca : v.s, vesicula seminalis.
“
much smaller in young specimens: they are situated close
to one another, at about the level of the anterior border of
the thighs.
210, The vas deferens (v.d), a delicate, white tube,
convoluted in the adult, but straight in the young, arising
trom the inner face of each testis, and passing directly
THE PIGEON, 229
backwards to the cloaca (c/), where it ends in a dilatation,
the vesicula seminalis (v.s) (see § 231, p. 236).
Ln the female.
‘211. The ovary (Fig. 53, ov), a single mass of irregular
form, situated at about the same level as the testes (§ 209),
but somewhat to the left side: it is made up of a number
of globular bodies or capsules, each containing an
ovarian egg, which, in the adult, vary from the size of
a cherry downwards, while in the young bird none may be
larger than a pin’s head. The single ovary represents that
of the left side : a rudiment of the right ovary is sometimes
present.
212. The (left) oviduct (Zod), a convoluted tube, with
stout walls, about a third of an inch in diameter in the
adult, and lying to the left side of the pelvic cavity:
posteriorly it enters the left side of the cloaca (see § 232),
anteriorly it dilates into a large funnel-shaped termination
(Zod”\, with delicate membranous walls, and having an
antero-posterior diameter of about an inch, which puts the
cavity of the oviduct in communication with the ccelome
(od). As some difficulty will’ probably be experienced
in distinguishing between the funnel-like extremity of the
oviduct and the peritoneum which supports it, the dissection
should be performed under water.
213. The rudiment of the right oviduct (70d), a
small blind tube, usually about half an inch long, but
varying in size in different individuals, attached to the right
side of the cloaca.
Ln both sexes.
214. The kidneys (Figs. 52 and 53, 4), dark red bodies,
situated immediately posterior to the lungs, and in close
contact with the dorsal body wall: each consists of three
well marked lobes—an anterior, a middle, and a posterior—
239 ZOOTOMY.
which are embedded in cavities furnished by the pelvis and
sacrum.
215. The postcaval vein (vena cava inferior s.
posterior,) (Fig. 54, Aéc), a large vessel passing from between
the anterior ends of the kidneys to the posterior dorsal
region of the right lobe of the liver: it enters the substance
Fic. 53.—Columba livia. The urinogenital organs of an adult
female, ventral aspect (x 3).
The peritoneum is removed, but the parts are 7 sifu, except that the
left oviduct is partly uncoiled.
ci.2, widdle, and ¢/.3, posterior, compartment of cloaca: 4, kidney ;
Zod, left oviduct: /.0a’, its opening into cloaca: 4a", its funnel-like
anterior end: /.0ad”, its opening into’ ceelome: ov, ovary; 7.0d, rudi-
mentary right oviduct: 7.0d’, its opening into cloaca: uw, ureter: w7’,
its opening into cloaca.
of that gland, and, emerging from its anterior border, passes
forwards to the heart (§ 246): it is formed posteriorly by the
union of the two iliac veins (§ 218), which carry the
THE PIGEON, 231
returning blood from the kidneys and reproductive organs,
as well as from the hind limbs.
216, The ureter (Figs. 52 and 53, wr), a delicate, mem-
branous tube, arising from the ventral face of each kidney,
between its anterior and middle lobes, and passing back-
wards to the cloaca (see § 230, p. 235), in the male parallel
and internal to the corresponding vas deferens, in the
female dorsal to the oviduct. In dissecting out the ureter
be careful not to injure the renal (§ 220) or the hypogastric
(§ 218) vein.
217. The adrenals or supra-renal bodies (Fig. 52,
adr), irregular yellowish organs near the anterior end of the
kidneys, and closely connected with the iliac veins.
XXXIII. Dissect away, with great care, the testes or
the ovary from the kidneys, also dissect out the
vasa deferentia or the oviduct, taking care not to
injure the renal vein (§ 220): turn the reproductive
organs and the rectum backwards so as to expose
more completely the kidneys and the roof of the
pelvic cavity : then dissect out
218. The renal portal or hypogastric veins (Fig.
54, ~p), paired vessels, uniting with one another in the
middle line immediately behind the kidneys, and from the
point of union sending off a trunk which, uniting with the
veins from the cloaca and rectum, forms the coccygeo-
mesenteric vein (¢2.7'): at its anterior end each renal
portal vein penetrates the posterior lobe of the kidney.
A small median caudal vein (c) bringing blood from the
the uropygium pours its blood into the point of union of
the renal portals, each of which also receives, just as it
enters the kidney, a larger internal iliac vein (2.2/7) from
the roof of the pelvis.
rpre a.ao ff
a
Pew
ren
plcy—
|) te
Se ieee] amt
Late”
Fic. §4.—Columba livia, The blood vascular system, from the
ventral aspect (nat. size).
: THE PIGEON. 233
The arteries are distinguished by transverse, the veins by longitudinal
shading: only the anterior and posterior portions of the vessels of the
neck (carotids and jugulars) are shown: the kidneys are represented in
outline, the right (left of figure) being, supposed to be partly dissected
away to show the vessels traversing it: the apex of the heart and the
coccygeo-mesenteric vein (¢..v) are displaced to the lefi.
a.ao, arch of the aorta: a@./z.a, anterior mesenteric artery: a.7.,
afferent renal veins : @.r.v’, vein bringing blood from pelvis into renal
portal system: é7.a, brachial artery: dr.v, brachial vein: ¢, caudal
artery and vein: ¢.¢c. common carotid artery: c.w.v, coccygeo-mesen-
teric vein : c@.a, coeliac artery: d.ao, dorsal aorta : e.c, external carotid
artery : edg, epigastric vein: ¢.r.v, efferent renal veins: fa, femoral
artery : fv, femoral vein : 4.v, hepatic vein : 7.c, internal carotid artery :
7,22, internal iliac artery and vein : z.z, internal mammary artery and
vein : 7#,@, innominate artery: z.v, iliac vein: faz, jugular vein: jw’,
anastomosis of jugular veins: /.az, left auricle : fis, tele Bilinonar
artery: Zpre, left precaval vein : /.7, left ventricle : pc, left pectora
arteries and veins: Zc.a, right pectoral artery : gc.v, right pectoral vein :
p.m.a, posterior mesenteric artery : fc, postcaval vein: 7.1, anterior,
r.a.2, middle, and r.a.3, posterior, renal artery : 7.az, right auricle :
rp, renal portal vein: 7.f.a, right pulmonary artery : prc) right, pre-
caval vein 5 7.v, renal vein: vw, right ventricle: sca, Sciatic artery :
sev, sciatic vein: sc/.a, subclavian artery: vv, vertebral artery and
vein.
219. The femoral vein (fv), a large trunk returning
the greater part of the blood from the leg,” and passing
between the anterior and middle lobes of the kidney to join
the iliac vein.
Just after entering the body cavity from the leg, the femoral receives
a small vein, which runs along the ventral edge of the pubis, and collects
the blood from the side wall of the pelvis.
220, The principal renal vein (7.z), a large longitudinal
vessel on the ventral surface of the kidney, entering the
iliac vein at its junction with the femoral.
The renal vein receives several efferent renal veins (¢.7.v) from the
middle and posterior lobe of the kidney : the blood from the anterior
lobe is poured by a separate efferent vein directly into the iliac.
1 If the muscles are to be dissected in the same specimen, it will
be advisable to defer tracing the blood-vessels into the leg for the
present, and to follow them at a later stage (see §§ 328—337, pp. 252-
254), pari passi with the dissection of the muscles of the thigh.
234 ZOOTOMY.
221. The dorsal aorta (d.ao), a small artery lying in the
middle line between the kidneys.
XXXIV. Carefully dissect away one of the kidneys, bit
by bit, taking care not to injure the veins in
connection with it: make out:
222. The renal portal vein (7.2), passing through the substance of the
kidney to join the femoral just external to the point where the latter
unites with the renal vein: during its course through the kidney, the
renal portal gives off several small afferent renal veins (a.7.v) to the
middle and posterior lobes, the anterior lobe being supplied by similar
vessels springing from the anterior face of the femoral vein : the renal
portal is joined near the hinder boundary of the kidney by one or two
smal] veins from the sacral region (2.7.v’).
223. The femoral artery (fa), given off from the
aorta between the anterior ends of the kidneys, and passing
almost directly outwards to supply the anterior region of
the thigh: it leaves the body cavity ventral to the pelvis,
and is accompanied by the femoral nerve (§ 293).
As the femoral artery leaves the body cavity, it sends
off a small vessel which passes along the ventral border of
the pubis, accompanying the vein already seen (§ 219), and
a branch of the obturator nerve (§ 293).
224. The sciatic artery (sca), given off from the
aorta at about the junction of the anterior and middle
lobes of the kidney; it passes outwards and backwards
through the substance of the kidney, emerges from that
organ at the junction between its middle and_ posterior
lobes, leaves the body cavity through the ilio-sciatic foramen
(§ 104) to reach the thigh, and then passes slightly forwards
as well as outwards so as to assume a course parallel to the
femoral vein. It is accompanied by the great sciatic
nerve (§ 294).
225. The sciatic vein (sc.v), bringing blood from the
posterior part of the leg; it runs parallel to the proximal
THE PIGEON. 235
portion of the sciatic artery, and debouches into the renal
portal vein.
226. The posterior (or inferior) mesenteric artery
(p.m.a), springing from the dorsal aorta at about the level
of the posterior border of the kidneys, and going to supply
the rectum and cloaca: beyond its origin the aorta becomes
the caudal artery (c), which passes backward parallel and
ventral to the caudal vein, and from the same point the
internal iliac arteries (¢/), are given off, which
accompany the corresponding veins (§ 218).
227. The renal arteries, of which there are three to each kidney :
an anterior (7a.1), springing from the dorsal aorta just anterior to the
origin of the femoral artery, and supplying the anterior lobe; a middle
(r.a.2), arising from the sciatic artery near the point where it enters the
kidney and passing forwards to the middle lobe ; and a posterior (7.2.3),
arising from the sciatic a little external to the last, and passing backwards
to the posterior lobe.
228. The origin of the coeliac (cw.a) and anterior
mesenteric arteries (a.7.a) (§§ 200, 203), from the
dorsal aorta.
XXXV. Remove the ventral wall of the cloaca, and
note :
229. Its division into three compartments (Figs. 52, 53,
and 55), separated from one another by incomplete parti-
tions ; the anterior chamber (¢.1) is almost globular when
distended, and receives the rectum; the middle chamber
(cf.2) is small, separated from the first by an annular fold
of the cloacal wall, and receives the urinary and genital
ducts (§§ 230—232): the posterior chamber (c/.3) is
separated from the middle by a low annular ridge, contains
the aperture of the bursa Fabricii (§ 233), and opens
externally by the vent.
230. The small round apertures of the ureters (wr)
in the dorsal wall of the middle chamber.
236 ZOOTOMY.
231. In the male the genital papille (Fig. 52, 2.2’)
conical elevations just external to the urinary apertures: on
their apices are the apertures of the vasa deferentia.
232. In the female the aperture of the left oviduct
(Fig. 53, 20a’), a considerable opening just external to that
of the left ureter: the rudimentary right oviduct has a
Fic. 55.—Columba livia. The cloaca of a young female. A, opened
from the ventral aspect ; B, in longitudinal section (nat. size).
&.f, bursa Fabricii : 6/’, its opening into posterior chamber of cloaca:
ceZ.1, anterior, c/.2, middle, and c/.3, posterior, chamber of cloaca : od,
opening of oviducts into middle chamber of cloaca: 7, rectum: zr,
opening of ureters into middle chamber of cloaca.
small opening (”0d’) similarly situated on the right side:
in the young bird the two apertures are of equal size
(Fig. 55, 0d).
233. The aperture of the bursa Fabricii (Fig. 55, 2./’), a small,
crescentic opening in the middle of the dorsal wall of the posterior
chamber : by drawing the cloaca backwards, and gradually dissecting it
away from its attachments, the bursa is seen as an ovoid, somewhat
flattened sac (4./), with glandular walls, situated between the dorsal
wall of the cloaca and the roof of the pelvic cavity: it is best de-
veloped in young individuals, when it may attain a length of a quarter
to three-quarters of an inch ; in the adult it is usually absent.
THE PIGEON. 237
XXXVI. Dissect off the pericardium : carefully clear
away the connective tissue and fat from the vessels
connected with the base of the heart, and trace
them out as far as is necessary to verify the
following descriptions: make out :
234. The separation of the heart into an anterior, dark,
thin-walled auricular division, and a posterior, lighter
coloured, thick-walled ventricular division of a conical
shape: the two divisions are separated by a line of fat,
which should be carefully removed.
235. The left ventricle (Fig. 54, Zv2), forming the
apex of the heart as well as the left convex side of the
ventricular division : it is very firm and hard to the touch.
236. The right ventricle (r.vz), much softer to the
touch than the left, and forming the right concave side of
the ventricular division.
237. The right auricle (7.az), forming the right half of the
auricular division, and usually gorged with blood after death.
238. The left auricle (/.a), usually in a more collapsed
state than the right.
239. The innominate arteries (cz.a), two large trunks
apparently proceeding from the centre of the base of the
heart, and diverging from one another like the limbs of a V:
each passes forwards and outwards, and divides into two
arteries, the common carotid («c), which proceeds almost
directly forwards, and the subclavian (sc/.a), which con-
tinues the direction of the innominate, and almost immediately
divides into two : of these the brachial or axillary artery
(ér.a) passes forwards and outwards, and curving round
at the shoulder enters the wing, which it supplies,! while
1 If the muscles are to be dissected in the same specimen, defer tracing
the blood-vessels of the wing until its muscles are examined (see
§§ 320—327).
238 ZOOTOMY.
the pectoral artery (fc) continues the direction of the
innominate and subclavian, which it nearly equals in calibre,
and supplies the pectoral muscles.
240, The internal mammary artery (z.7.), a small vessel given off
from the posterior surface of the subclavian : it passes backwards along
the inner surface of the ribs,and gives off transverse intercostal arteries
to the intercostal spaces.
241. The arch of the aorta (a.ao), situated immediately
external to the right innominate artery, of which it has the
appearance of being a branch: the aorta is, however, the
principal artery arising (see § 274) from the left ventricle,
and the innominates are branches given off immediately
after its origin, and, owing to the immense size of the
pectoral muscles which they supply, exceeding the re-
mainder of the main trunk in calibre: the aorta is seen
to pass forwards and slightly outwards or to the right;
its further course will be seen at a later stage (§ 257).
242. The pulmonary artery situated just external to
the left innominate, and springing from the ventral side of
the base of the heart (see § 269); almost immediately after
its origin it divides into two trunks, the left of which (4/.2)
passes forwards and outwards, parallel to the left innominate,
while the other (7.f.2) turns to the right and passes to the
dorsal side of the innominates.
243. The right precaval veins (vena cava superior s.
anterior dextra,) (7.p7c), a large vessel situated dorsal and
external to the right innominate artery: it is formed by the
union of three veins, the jugular (jw) (§ 249) from the
neck, the brachial (47.v) from the wing, and the pectoral
(fev) from the pectoral muscles: posteriorly it enters the
right auricle at its anterior end.
244. The internal mammary vein (7.7), taking a parallel course to
the artery of the same name (§ 240), and entering the pectoral vein close
to its junction with the jugular and subclavian.
THE PIGEON, 230
245. The left precaval vein (vena cava superior s.
anterior sinistra), (Z.f7c), similarly related to the left innomi-
nate artery, and receiving veins symmetrical with those of
its fellow: it passes backwards to the dorsal side of the
heart, where its further course will be seen subsequently
(§ 254).
246. The postcaval vein (/éc) has already been seen
($ 215): after emerging from the liver it passes directly
forwards and enters the right auricle on the right side of
its dorsal wall.
247. The course of the common carotid arteries
(cc), made out by removing the crop and dissecting away
the ventral muscles of the.neck: each passes forwards and
inwards towards the middle line of the neck, and runs
parallel and close to its fellow along the ventral aspect of
the cervical vertebrze: about an inch behind the head, the
arteries diverge again, and each, passing forwards and
slightly outwards, divides into an external carotid (e.¢),
supplying the head generally, and an internal carotid
(zc), supplying the brain.
248. The vertebral artery (v7), arising from the common
carotid in the root of the neck : it passes to the lateral aspect
of the neck, and, dipping between the muscles, enters the
vertebrarterial canal, and passes forwards to supply the
brain and spinal cord.
249. The course of the jugular veins (jw): they are
united with one another by a transverse commissure (7#’) on
the under surface of the skull just behind the velum palati
(§ 299);—this is best seen by dissecting away the anterior
part of the gullet from the neck muscles and turning it as
far forwards as it will go.
The commissural branch receives veins from the palate, and the
jugulars themselves from various parts of the head : further back each
240 ZOOTOMY.
jugular receives veins from the crop, the sides of the neck, and the
lymphatic glands ($ 251), and at the level of the posterior end of the
latter, the vertebral vein (vr) enters it.
250. The cervical portion of the vagus, a stout nerve
accompanying the jugular. -
251. The cervical lymphatic glands, paired, reddish,
ovoidal bodies, situated one on each side of the root of the
neck : each receives an artery from the common carotid, and
contributes a vein to the jugular.
XNXVIL. Carefully dissect away the liver substance from that part
of the postcaval which is embedded in it, and make out :
252. The right and left hepatic veins (4.v), of which the latter is
the larger, entering the postcaval just before its exit from the liver.
253. The epigastric vein (e/g) (§ 180), entering the left hepatic vein
near its junction with the postcaval.
XXXVIII. Ligature the postcaval between the liver
and the heart, and cut it through to the distal side
of the ligature : turn the apex of the heart forwards
and make out:
254. The left precaval (Fig. 56, 2.47c) curving round the
dorsal side of the left auricle to reach the right auricle.
255. The pulmonary veins ({.v), entering the left
auricle in the U-shaped space between the two precavals:
sometimes there is a single trunk from each lung, sometimes
there are two from each, uniting before they enter the
auricle.
256. The course of the right and left pulmonary
arteries (77.2, /.p.a) (§ 242) to the lungs.
257- The arch of the aorta (a.av) (§ 241), curving
over the right bronchus to reach the middle dorsal line,
when it becomes the dorsal aorta (§ 221, Fig. 54, d.ao).
XXXIX. Cut through the precavals, the pulmonary
arteries and veins, and the aorta, and remove the
heart from the body : place it in a dissecting dish
THE PIGEON, 241
under water, and note carefully the relations of
the great vessels already seen, especially those. of
the pulmonary veins: then remove the outer walls
of both auricles, wash out the contained blood,
and make out:
258. The septum auricularum, a thin muscular parti-
tion separating the auricles from one another.
Fic. 56.—Columba livia, The heart, viewed from the dorsal
aspect (nat. size). . ; d
a.ao, arch of aorta: br.a, brachial artery : br.v, brachial vein: ¢.c,
common carotid ; jw, jugular ; /.az, left auricle: /.2.a, left pulmonary
artery : pve, left precaval: /.vm, left ventricle: rau, right auricle :
y.au’, its smooth-walled dorsal portion receiving the pre- and post-
cavals: 7.g.a, right pulmonary artery: 7.prc, right precaval: v7,
right ventricle.
259. The entrance of the right precaval, in the anterior
wall of the right auricle.
260, A tunnel-like passage in the dorsal region of the
same chamber, leading into the left precaval.
R
242 ZOOTOMY.
261. The aperture of the postcaval, in the postero-
external wall of the right auricle, and guarded by a valvular
fold of muscle, the Eustachian valve.
262. The fossa ovalis, a thin place in the septum
auricularum, marking the position of the embryonic foramen
ovale by which the two auricles were placed in communica-
tion with one another: it is best seen by holding the septum
auricularum up to the light.
263. A deep depression in the dorsal wall of the left
auricle, into which the pulmonary veins open.
XL. Cut away both auricles, and all but the origins of
the aorta and pulmonary artery, and, looking at
the base of the ventricles, note :
264, The rounded left auriculo-ventricular aperture,
guarded by the two membranous flaps of the mitral valve.
This and the other valves are best seen by filling the
ventricles with water and then squeezing them; at every
squeeze the auriculo-ventricular valves close, when the
pressure is removed they open, and if a sufficient length of
the aorta and pulmonary artery is left, the semilunar valves
close.
265. The crescentic right auriculo-ventricular aper-
ture, guarded on its outer or convex side by the large,
fleshy, right auriculo-ventricular valve (§ 268).
266. The rounded apertures of the aorta and pulmonary
artery, each guarded by three membranous semilunar
valves (§ 260).
XLI. Open the right ventricle by a V-shaped incision,
introducing the scissors into the cut end of thd
pulmonary artery, cutting obliquely backwards to
the apex of the ventricle, and then turning sharply
round and passing obliquely forwards, nearly to
the anterior border of the ventricle: note:
THE PIGEON, 243
267. The convex right face of the septum ventri-
culorum, or partition between the ventricles, projecting so
much into the cavity of the right ventricle as to make it
crescentic in section.
268. The right auriculo-ventricular valve, a large
flap of muscle, attached partly to the outer edge of the
auriculo-ventricular aperture, partly to the outer wall of the
ventricle, and depending into the cavity of the latter.
269. The origin of the pulmonary artery from the left side
of the anterior end of the ventricle: at the base of the artery
the three pocket-shaped pulmonary semilunar valves.
270. The columne carnee, fleshy ridges into which
the wall of the ventricle is raised.
XLII. Remove the outer wall of the left ventricle, and
note:
271. The great thickness of its wall in comparison with
that of the right ventricle.
272. The concave left side of the septum ventriculorum.
273. The two membranous flaps of the mitral valve,
connected by delicate tendons, the chorde tendinez,
with small conical elevations of the ventricular wall, the
musculi papillares.
274. The aperture of the aorta, guarded by three pocket-
shaped aortic semilunar valves.
XLIII. Note in the body-cavity, now the heart is
removed :
275. The backward continuation of the gullet, dorsal to
the trachea, to join the proventriculus.
276. The remains of the intermediate (§§ 160, 169) and posterior
(§ 159) air-sacs, the ventral walls of which will have been removed ;
they are best seen under water: the anterior-intermediate air-sac
covers the greater part of the ventral surface of the lung, the posterior-
intermediate lies immediately posterior to the lung: in the antero-
dorsal region of the posterior-intermediate and posterior sacs are seen
R 2
244 ZOOTOMY.
apertures by which they respectively communicate with the lung; the
corresponding apertureof the anterior intermediate is in its antero-
internal corner, The apertures of the other air-sacs are much more
diffcult to see: that of the sub-bronchial (§ 164) lies in its posterior
wall just dorsal to the entrance of the bronchus into the lung: the
prebronchial extends backwards to the anterior end of the lung and
there opens (see § 286),
277. The costo-pulmonary muscles, small fan-
shaped sheets of muscle, arising from the junctions of the
sternal and vertebral ribs, and passing into an aponeurosis
which covers the ventral surface of the lungs, between the
dorsal walls of the air-sacs and the pleura.
278. The pulmonary pleura, a delicate membrane,
continuous with the peritoneum and immediately investing
the ventral surface of the lungs: to see it the costo-
pulmonary muscles and their aponeurosis must be removed.
XLIV. Cut through the trachea about an inch anterior
to its bifurcation: dissect away the lungs from the
dorsal body wall and remove them from the body
with the bronchi and posterior end of the
trachea: note:
279. The transverse depressions on the dorsal surface of
the indistensible lungs, corresponding to the ribs, and the
intervening elevations which fit into the intercostal spaces.
280. The dilatation of the posterior end of the trachea
into the syrinx (Fig. 57, sy), or “lower larynx.”
281, The intrinsic syringeal muscles, paired narrow
bands arising from the sides of the trachea about an inch in
front of its bifurcation, and passing backwards to be inserted
into the sides of the syrinx.
282. The complete tracheal rings, their ventral halves
bony, their dorsal halves cartilaginous.
283. The bronchial half-rings, along the outer side of
each bronchus ; the first is bony, the rest are cartilaginous:
THE PIGEON. 245
the inner face of each bronchus is flat and membranous, and
constitutes the membrana tympaniformis interna.
tr
spb
pe
} pt
Fic. 57.—Columba livia. The lungs, filled from the trachea with
a solid injection and viewed from the ventral aspect (nat. size).
In the left Jung the bronchus (47, 47’) is traced to its termination by
dissecting away the overlying substance of the lung.
4r, principal bronchus: 47, 67”, 67”, secondary bronchi: 7.2,
pulmonary artery : #.v, pulmonary vein: sy, syrinx: zy, trachea: s/.4,
aperture for prebronchial air-sac: sé.4, for sub-bronchial: @.7x, for
anterior-intermediate : f.77z, for posterior-intermediate : 2, for posterior
(ab lominal).
284. The modification of the tracheal rings in the syrinx: the two
posterior rings are more widely separated from each other than the rest,
and their bony ventral portions send median processes towards one
another, which are only separated by a small cartilaginous interval: on
the dorsal side these rings are incomplete, but are united with one
another on each side of the middle line by a longitudinal cartilaginous
‘bar: the bony first pair of bronchial half-rings are in contact with one
another dorsally and ventrally, and, with the distal tracheal rings just
described, inclose a chamber, the tympanum,
285. If the air-sacs, and consequently the lungs, are injected, the
secondary bronchi (47’, dr”, dr”) will be seen branching out over the
anterior and internal regions of the ventral surface of the lungs: they
246 ZOOTOMY.
have thin membranous walls, and in uninjected specimens are not
readily recognised. :
286. The apertures in the lung which communicate with the air-sacs,
also seen readily only in injected specimens: the aperture of the
posterior sac (f) is at the postero-external angle of the lung : that of the
posterior-intermediate (./) just anterior and external to the last : that
of the anterior-intermediate (a.27) at the end of a prominent secondary
bronchus on the ventral surface, just posterior to the entrance of the
principal bronchus: that of the sub-bronchial (s6.6) is also on the
ventral surface, just anterior to the entrance of the chief bronchus : and
that of the prebronchial (59.6) at the anterior end of the lung.
287. By tracing the principal bronchus through the lung (if un-
injected, this can be done by passing in a probe and cutting down upon
it), itis seen to pass backwards and outwards to the postero-external
corner of the lung, and then to divide into two short tubes, the
anterior and external of which is connected with the posterior-inter-
mediate air-sac (f.7), the posterior with the posterior sac (@é) : the tubes
which communicate with the other air-sacs are given off from a dilata-
tion of the principal bronchus, termed the vestibule, just after it
enters the lung. Soon after entering the lung the bronchus loses its
cartilaginous half-rings.
288. Both from the principal bronchus and the secondary bronchi,
tertiary bronchi are given off in a pinnate manner: these in their
turn give rise to tubes of the fourth order, and so on,
XLV. Sever the bronchi at their entrance into the
lungs, and open the syrinx, under water, by the
removal of its ventral wall: note :
289. The cushion-like lateral thickenings of the walls of
the tympanum, projecting into and narrowing its cavity : the
mucous membrane covering them is thicker than elsewhere.
290. The membrana semilunaris, a delicate, in-
conspicuous, vertical fold of mucous membrane, projecting
forwards from the posterior wall of the tympanum at the
point of bifurcation of the trachea: it is supported by a
delicate bar of cartilage—the pessulus—which extends
vertically between the adjacent dorsal and ventral extremities
of the first pair of bronchial half-rings.
THE PIGEON. 247
XLVI. Dissect away the remains of all the organs still
left in the body cavity, and make out on its
dorsal wall :
291. The thoracic spinal nerves, emerging from the
intervertebral foramina of the thoracic vertebra, and passing
transversely outwards parallel to and equidistant from the
vibs.
292. The brachial plexus, a network of nerves at
the root of the neck, formed by the union of the posterior
cervical and anterior thoracic spinal nerves: from it are
given off the nerves to the shoulder and wings.
293. The lumbar plexus, formed by the nerves which
emerge through the intervertebral foramina of the lumbar
vertebra: it gives off the femoral nerve to the front of
the thigh, and the small obturator nerve which traverses
the obturator fissure (§ 105) and goes to the muscles about
the acetabulum.
294. The sciatic plexus, formed by nerves emerging
from the intervertebral foramina of the sacral vertebra:
it goes mainly to form the great sciatic nerve which
accompanies the sciatic artery (§ 224).
295. The sympathetic nerves, delicate, paired, longi-
tudinal cords, running close alongside the vertebral column,
and having at intervals ganglia, which are connected with
the spinal nerves just at their exit from the intervertebral
foramina.
Posteriorly the two sympathetics unite in a single small ganglion
impar: anteriorly each forms a large posterior cervical ganglion
lying ventral to the brachial plexus, and thence passes along the verte-
brarterial canal, alongside the vertebral artery, to the head.
XLVII. Dissect away the skin from the dorsal surface
of the uropygium, and note:
296. The uropygial gland, a whitish, bilobed organ,
248 ZOOTOMY.
about a quarter of an inch long, with its backwardly directed
apex passing into a duct which opens in a distinct median
papilla.
XLVIII. Cut through one side of the lower jaw
near its articulation, open the mouth widely, and
observe :
297. The palate, or roof of the mouth, marked by a
median longitudinal slit, bounded by two fimbriated folds
of mucous membrane, between which are the posterior
nares.
298. At the posterior end of the palatal folds is the
single median aperture of the Eustachian tubes,
which communicates, right and left, with the tympanic
cavities (§ 318).
299. The velum palati, a bilobed flap of mucous
membrane, with fimbriated edges, forming the posterior
termination of the palate.
300. The tongue, pointed in front, bifid and fimbriated
behind.
301. The glottis, an oval aperture just behind the root
of the tongue, leading into the trachea: its margins are
slightly fimbriated, and immediately behind it is a bilobed
fimbriated fold of mucous membrane.
302. The wide pharynx, leading into the gullet.
303. By dissecting away the mucous membrane of the
glottis, the larynx is found, a cartilaginous apparatus form-
ing the anterior end of the trachea.
The larynx consists of the following parts :—(a) the thyroid, a
partly ossified cartilaginous plate, bent upon itself in the form of a
dorsally incomplete ring, wide and scoop-shaped ventrally, narrow
dorsally : (4) the cricoid, a small longitudinal rod of cartilage, inter-
posed between the dorsal ends of the thyroid: (c) the arytenoids,
paired, somewhat triangular cartilages, ossified at their proximal ends,
where they articulate with facets on the anterior end of the cricoid ;
THE PIGEON. 249
they form the actual supports of the glottis, The two anterior rings
of the trachea are incomplete dorsally, and the first has its dorsal
extremities fused with the thyroid.
XLIX. Cut away the outer wall of one of the nasal
cavities, first passing a probe from the anterior to
the posterior nares: note:
304. The elevation caused by the turbinal (§ 72), covered
by the delicate Schneiderian membrane.
305. The relations of the anterior and posterior nares
to the nasal cavity.
L. Remove the dorsal wall of the orbit: observe
the four straight and two oblique muscles, which
have the same relations as in the lower vertebrata
(see pp. 77, 78, §§ 191203) : remove the eye with
the nictitating membrane by cutting through its
muscles and the optic nerve: observe:
306. The lacrymal gland, a whitish irregular body in
the postero-dorsal region of the orbit.
307. The Harderian gland, a small pinkish body in
the anterior region of the orbit.
308. The form of the eye: its inner half has the usual
hemispherical figure, but its outer half is somewhat obtusely
conical.
309. The entrance of the optic nerve, in the centre of
the inner hemisphere.
310. The bursalis, a somewhat quadrate shoot of
muscle, arising from the dorsal region of the inner hemi-
sphere by a convex edge, and passing downwards to end in
aconcave edge just over the optic nerve: the lower edge
forms a tubular tendinous sheath.
311. The pyramidalis, a triangular muscle, arising
from the antero-ventral region of the inner hemisphere ; it
passes upwards and backwards, and, just in front of the
259 ZOOTOMY.,
optic nerve, ends in a tendon which passes through the
sheath of the bursalis, then proceeds downwards and _ back-
wards, curves round the postero-ventral margin of the eye-
ball, and finally passes forwards to be inserted into the edge
of the nictitating membrane.
312. The sclerotic, cornea, iris, and pupil have the
same relations as in other Vertebrata (see p. 84, §§ 224, 225).
313. The sclerotic plates, small fiat bones, arranged
in an imbricating manner round the sclerotic just external
to its junction with the cornea.
LI. Divide the eye, by an equatorial incision, into
inner and outer hemispheres : note :
314. The pecten, a black plaited structure, in the
antero-ventral region of the inner hemisphere, having a
curved free edge, and an attached edge which extends from
the entrance of the optic nerve downwards and forwards,
parallel to the course of the pyramidalis (§ 311): it consists
of a fold of the choroid, projecting through a fissure in the
retina. It should be removed and examined under a low
power of the microscope.
315. The choroid, retina, lens, and aqueous and
vitreous humours have the same relations as in the
other Vertebrata (see pp. 84, 85, §$ 224—228).
316. In the outer hemisphere, the choroid processes,
radiating folds, developed in the outer part of the choroid,
between the outer edge of the iris and the ora serrata
or free border of the retina.
LI. Cut away the walls of the external auditory
meatus ($ 128), and make out:
317. The tympanic membrane, a thin sheet of
fibrous tissue stretched across the bottom of the external
meatus,
318. By carefully removing the tympanic membrane, the
THE PIGEON. 251
tympanic cavity is reached, a small chamber, separated
from the external meatus by the tympanic membrane, and
communicating with the cavity of the mouth by the Eus-
tachian tube (§ 298), into which a bristle should be passed.
319. The relations of the columella to the tympanic
cavity (see § 61, p. 195).
LILI. Carefully remove the skin from the shoulder and
wing, and dissect off the fascia, a strong sheath
of connective tissue which covers the muscles,
until the following can be made out:
320. The tensor patagii longus, a small conical slip
of muscle, arising from the antero-external region of the
pectoralis major: it receives fibres from the tensor patagii
brevis (§ 325), and passes distally into a long elastic tendon,
lying in the border of the alar membrane (§ 135), and in-
serted into the skin on the pre-axial border of the manus.
321. The biceps, a large muscle forming the fleshy
mass in the anterior border of the upper arm, and acting as
the chief flexor of the fore-arm.
322. The triceps, forming the fleshy mass on the poste-
rior aspect of the upper arm, and acting as extensor of the
fore-arm.
323. The tensor patagii accessorius, a small
squarish mass of muscle lying in the proximal region of the
alar membrane: it arises from the fascia of the biceps ; its
anterior border is connected by fascia with the tendon of
the tensor longus, and from its posterior border a long stout
tendon is given off which passes outwards, soon becoming
parallel to the tendon of the tensor longus, and having a
common insertion with it.
324. The extensor metacarpi radialis longus, a
muscle forming the anterior or preaxial edge of the fore-
arm, and acting as extensor of the manus.
252 ZOOTOMY.
325. The tensor patagii brevis, a oroad sheet of
muscle covering the shoulder on its dorsal aspect ; it arises
from the dorsal ends of the coracoid and furcula, passes
backwards, parallel to the humerus and partly covering the
triceps, contributes fibres to the tensor longus, and is in-
serted by a broad tendon into the fascia of the extensor
metacarpi radialis longus.
326. The insertion of the subclavius (§ 166): the
muscle passes anteriorly into a tendon which proceeds for-
wards and outwards to the foramen triosseum: by cutting
through and reflecting the tensor brevis, the tendon is seen
to emerge from the foramen on its dorsal side and to be
inserted into the dorsal surface of the humerus, near the
greater tuberosity (§ 95): by pulling upon the muscle, the
wing is raised; the subclavius is the chief elevator of the
upper arm,
327. The insertion of the pectoralis major (g 153),
by cutting through and reflecting the biceps: its fibres
are gathered into a broad flat tendon which is attached
along the whole extent of the greater tuberosity: the pec-
toralis major is the principal depressor of the wing.
LIV. Remove the skin from the leg, and, by carefully
dissecting away the fascia, clear the muscles and
their tendons sufficiently to show:
328. The extensor tendons of the digits, on the
anterior (dorsal) side of the tarso-metatarsus : those of the
second, third, and fourth, or forwardly-directed digits, are
formed by the trifurcation of a single tendon, which, traced
into the shank, is found to be the tendon of insertion of a
small muscle, the extensor longus digitorum, which
arises from the anterior face of the proximal end of the tibia :
the extensor tendon of the first digit, or hallux, springs from
a small distinct muscle, the extensor hallucis brevis,
THE PIGEON. 253
which arises from the proximal end of the tarso-metatarsus,
Distally the extensor tendons run along the dorsal sides of
the digits, closely bound down by fascia, and are inserted
into the bases of the distal phalanges.
329. The gastrocnemius, a large muscle consisting of
distinct internal and external portions, and forming the
outer layer of the fleshy mass on the posterior surface of the
shank : its two heads arise respectively from the inner and
outer surfaces of the proximal end of the tibia, the internal
head arising also from the distal end of the femur: the two
heads unite in a broad, flat tendon, which is inserted into the
proximal end of the posterior surface of the tarso-metatarsus :
its action is to straighten the foot on the shank.
330. The flexor tendons of the digits, a large number
of readily separable tendons on the posterior (ventral)
surface of the tarso-metatarsus: traced into the leg they
are found to be the distal tendons of a number of separate
muscles, the fexores digitorum, which arise from the
posterior and lateral surfaces of the tibia; to see them the
gastrocnemius should be cut through and reflected. Distally,
the flexor tendons can be traced into the toes, either two or
three to each (see §§ 331—334).
331. In the fourth or outermost toe there are two flexor tendons,
one being superficial or ventral to the other : the superficial or per-
forated tendon (springing from the flexor perforatus muscle) sends
off lateral slips to the proximal phalanx, and then forks, one division
going to each side of the second and third phalanges: the deep or
perforating tendon, lying between the former and the bone, passes
between the division of the perforatus, along the ventral surface of the
phalanges, and is inserted into the proximal end of the distal phalanx.
332. In the third digit the arrangement is complicated by the presence
of two perforated tendons : of these the bifurcations of one are inserted
into the proximal, those of the other into the second, phalanx : so that
through the fork of the first or superficial perforated tendon both the
second perforated and the perforating tendons pass,
254 ZOOTOMY.
333. In the second digit the arrangement is similar, except that the
first or superficial perforated tendon, instead of forking, forms a
sheath for the other two tendons at the proximal end of the first phalanx,
334. In the first digit or hallux, there are only two flexor tendons ;
of these the perforating tendon is superficial, and the perforated forms a
sheath for it at the proximal end of the first phalanx.
335. The perforating tendons of the second, third, and fourth digits
are all formed by the trifurcations of a single tendon, lying deeper
than the perforated tendons, and belonging to a large muscle, the
peroneus medius: this tendon is joined by a slip from that of
the flexor perforans, which is continued to form the perforating
tendon of the hallux.
336. The ambiens, « small, slender muscle, lying superficially on
the inner surface of the thigh, just over and parallel to the femur: it
arises from the pubis immediately ventral to the acetabulum : distally it
passes into a long, slender tendon, which, on reaching the knee, pene-
trates the fibrous capsule of the joint, curves round to the outer side,
passing at the same time distalwards, and finally joins the flexor
perforatus of the second and third digits.
337. If, on the undissected side, where the tendons are
not displaced, the shank is flexed on the thigh and the
tarso-metatarsus on the shank, as in perching, the toes will
undergo complete flexion : this is chiefly due to the fact that
in the flexion of the tarso-metatarsus on the shank the flexor
tendons of the toes are put upon the stretch as they pass
the mesotarsal articulation (§ 117): it is also aided by
the flexion of the shank upon the thigh producing tension
of the ambiens tendon, which, in its turn, acts upon the
flexors of the digits.
LV. In the hardened brain notice the following external
characters :
338. The medulla oblongata (Fig. 58, m0), con-
tinuous behind with the spinal cord, and like it composed
externally of white matter : ! it greatly exceeds the cord in
} The distinction between white and grey matter is not obvious in the
hardened brain; it is therefore convenient to have a freshly removed
brain for comparison.
ee ey
THE PIGEON. 255
diameter, and at the junction of the two there is a strong
ventral flexure: it is marked ventrally with a median longi-
tudinal groove, separating the ventral pyramids: on the
upper side are the dorsal pyramids, which, passing from
behind forwards, diverge, leaving a median dorsal hollow,
the fourth ventricle (Fig. 59, v.4).
pr olf
yw
¥ VIVE x X
Fic. 58.—Columba livia, The brain. A, from above; B, from
beneath ; C, from the left side (x 2). eink
cb, cerebellum: ¢.4, cerebral hemispheres: f, flocculus : z#/, infun-
dibulum : #.0, medulla oblongata : 0./, optic lobes : off, olfactory lobes :
o.t, optic tracts: pz, pineal body: I-XII, roots of cerebral nerves:
5f.1, root of first spinal nerve.
256 ZOOTOMY.
339. The cerebellum (Fig. 58, <2), a median, laterally
compressed, crest-like mass, lying above the anterior part of
the medulla oblongata ; it is marked by transverse furrows or
sulci, between which are elevations or gyri: on the lateral
surfaces of the cerebellum the sulci and gyri radiate from
an area on which is a slight elevation, the flocculus (/):
the cerebellum has a pink tint in the fresh brain, being
composed externally of grey matter.
340. The optic lobes (0./), paired, white, ovoidal bodies,
situated one on either side, immediately in front of the
medulla and below the cerebellum.
341. The cerebral hemispheres (c.4), paired, obtusely
conical bodies, in close contact with one another, and
situated immediately in front of the cerebellum and optic
lobes, with both of which their hinder surfaces are in contact:
they consist externally of grey matter.
342. The pineal body (fz), a small rounded mass on
the dorsal surface of the brain, wedged in between the
cerebral hemispheres and the cerebellum.
343. The olfactory lobes (//), small blunt projections,
connected one with the anterior end or apex of each
cerebral hemisphere : from them the olfactory nerves
(first pair of cerebral nerves) are given off to the nasal sacs,”
344. The optic tracts (0.7), forming a broad, white
transverse band, concave forwards, between the optic lobes,
on the lower surface of the brain: from their anterior
median region the optic (second) nerves (11) spring.
345. The infundibulum (¢7/), a rounded area with
a central aperture, just posterior to the optic tracts: to
it is attached the pituitary body, which is usually
detached in removing the brain from the skull.
346. The third nerve (i), arising close behind the
infundibulum, a short distance from the middle line, from a
THE PIGEON. 257
part of the brain not separated off from the medulla oblongata,
but answering to the crura cerebri.
347. The fourth nerve (rv), arising from the dorsal
side of the medulla oblongata at its anterior end: it emerges
between the medulla and the cerebellum, and passes down-
wards in the groove between the medulla and the optic lobe
to reach the ventral surface of the brain.
348. The fifth nerve (v), a large trunk arising from the
lateral surface of the medulla oblongata just behind the
optic lobe: its fibres extend upwards quite to the dorsal
edge of the medulla.
The fifth nerve arises by two roots, the larger of which presents an
enlargement, the Gasserian ganglion,
349. The sixth nerve (vi), arising from the ventral
surface of the medulla near the middle line and just internal
to the point of origin of the fifth.
350. The seventh nerve (vi), a small trunk arising
close behind the fifth.
351. The eighth or auditory nerve (viti), a large, soft
trunk arising close behind the seventh : its fibres are traceable
upwards to the dorsal pyramids of the medulla.
352. The ninth (1x), tenth (x), and eleventh (xt)
nerves, arising together close behind the eighth: they
have small roots, the tenth (vagus) being the largest, and
the eleventh (spinal accessory) distinguished by being
traceable upwards and backwards alongside the medulla
oblongata to the spinal cord, from which it arises between
the roots of the spinal nerves, also receiving fibres from the
medulla.
353. The twelfth nerve or hypoglossal (xt), a
small trunk arising from the ventral surface of the medulla
internal to the eleventh.
258 ZOOTOMY.
LVI. Separate the hemispheres from one another by
gently pressing them outwards, noting the absence
of any connection between them: make a small
incision in the inner wall of one of them near its
postero-dorsal corner, so as to lay bare its cavity
(§ 357): carefully cut away enough of the inner
and posterior walls of the hemisphere to expose
the whole of this cavity: also remove the cere-
bellum by cutting through its lateral attachments
to the medulla oblongata (§ 354): note:
354. The attachment of the cerebellum to the medulla by
strong, paired pillars of white matter, the peduncles (Fig.
59, A, £): from its attachments the cerebellum extends
backwards over the medulla and forwards between the
optic lobes,
355. The optic commissure (0.c), a flat, horizontal
band of white fibres uniting the optic lobes beneath the
anterior prolongation of the cerebellum.
356. The thalamencephalon (4c), lying immediately
in front of the optic commissure, and hidden in the entire
brain by the meeting of the cerebral hemispheres with the
cerebellum: it consists of small paired masses cf grey
matter, the optic thalami, which, if the dissection has
been carefully conducted, will be seen to be covered by a
thin sheet of pia matter full of blood-vessels, the velum
interpositum : this is best seen in a fresh brain.
357. The lateral ventricle, or cavity of the cerebral
hemisphere, an irregular chamber with very thin inner,
upper, and posterior walls, but having its floor thickened
and its dimensions greatly diminished by a large mass of
white matter, the corpus striatum (c.s).
358. The third ventricle (v.3), a vertical cleft between
the optic thalami, roofed over by the velum interpositum,
THE PIGEON. 259
and bounded in part by a thin plate of grey matter, the
lamina terminalis, (27).
Fic. §9.—Columba livia, The brain. A, dissected from the dorsal
aspect; B, in longitudinal vertical section (x 2).
In A, the hemispheres are somewhat displaced outwards, and the roofs
of the right lateral and optic ventricles are removed, as well as the
cerebellum and the velum interpositum. :
a.c, anterior commissure : cb, cerebellum : ¢., cerebral hemispheres :
c.s, corpus striatum : fm, foramen of Monro: inf, infundibulum : 7.0,
medulla oblongata: 0.c, optic commissure: 0.ch, optic chiasma: 0./,
optic lobes : off, olfactory lobes : 0.v, optic ventricle: #, peduncles of
cerebellum : #.c, posterior commissure: fz, pineal body: fc, thala-
mencephalon : v.3, third ventricle: 7.4, fourth ventricle.
B 2
260 ZOOTOMY.
359. The foramen of Monro (fm), a small aperture in
the inner wall of the lateral ventricle at the level of the
anterior end of the thalamencephalon : it communicates with
the third ventricle and transmits a vascular fold of pia
mater, the choroid plexus, which is continuous with
the velum interpositum.
360. The anterior commissure (a.c), a white, trans-
verse cord connecting the corpora striata with one another,
and lying just below the foramina of Monro.
361. The posterior commissure (#.c), a similar cord
uniting the thalami immediately in front of the optic
commissure.
362. The fourth ventricle (7.4), a wide flat cavity on
the dorsal surface of the medulla oblongata, covered, in the
entire brain, partly by the cerebellum, partly by pia mater.
LVII. Carefully remove the optic commissure and the
dorsal wall of one or both optic lobes: observe :
363. The aqueduct of Sylvius (Fig. 59, B), a
median passage placing the third and fourth ventricles in
communication with one another.
364. The optic ventricle (Fig. 59, A, 0.7), a cavity in
each optic lobe, communicating internally with the aqueduct
of Sylvius, and with it representing the simple mesoccele of
the lower Vertebrata (see § 181, p. 73, and § 86, p. 23).
LVIII. Make a longitudinal vertical section of another
hardened brain, and note :—-
365. The continuity of the third ventricle, aqueduct of
Sylvius, and fourth ventricle (Fig. 59, B, 7.3, 7.4).
366. The relation of the foramen of Monro (fm) to the
third ventricle, and of the apertures of the optic ventricle to
the aqueduct of Sylvius.
367. The downward continuation of the third ventricle
into the infundibulum (z7/).
THE PIGEON. 261
368. The relations of the anterior (a.c), posterior (.c),
and optic (0.c) commissures.
369. The arbor vite, or foliated appearance produced
in the section of the cerebellum by the superficial grey
matter being continued inwards into the sulci, and investing
the outward prolongation of the central white matter into
the gyri. Ifa second brain is not at hand, this may be seen
in a section of the cerebellum removed in § LVI: it is best
seen, however, in a fresh brain.
THE RABBIT (Lepus cuntculus).
A.—THE SKELETON.
I. It is advisable to have two skeletons for examin-
ation, one of an adult animal, the other of a
specimen about six weeks old; the latter is the
more important of the two. In the adult skeleton
the bones are best kept in their natural connection,
in the young specimen they should be all sepa-
rated from one another by prolonged maceration,
or by boiling for a short time in water. Of the
entire skull a longitudinal vertical section should
be made with a fine saw.
II. In the skeleton as a whole, make out its division
into
1. The axial skeleton, consisting of the skull (§ 4)
and vertebral column, with the ribs and sternum.
2. The appendicular skeleton, consisting of the
shoulder-girdle (§ 5), the hip-girdle or pelvis (§ 6),
and the fore- and hind-limbs.
3. The division of the vertebral column into regions:
the cervical region, containing the seven ribless vertebre
which immediately follow the head ; the thoracic region,
THE RABBIT. 263
consisting of twelve or sometimes thirteen rib-bearing ver-
tebre ; the lumbar region, containing seven or some-
times six large vertebrze without ribs; the sacral region,
consisting of four vertebrae more or less completely fused
intoa single bone, the sacrum; and lastly, the caudal
region, containing about fifteen vertebrae, which extend
from the sacrum to the end of the tail.
4. The skull, consisting of the skull proper (brain-case
and upper jaw), the lower jaw or mandible, and the
tongue-bone or hyoid.
5. The shoulder-girdle, consisting on each side of the
scapula, or blade-bone, and of the smal! clavicle, or
collar-bone.
6. The hip-girdle, consisting of large paired bones,
the ossa innominata, united both with one another and
with the sacrum.
7. The fore-limb, divisibie into three parts: a proximal
division, consisting of a single bone, the humerus; a
middle division, containing two bones, an inner, the radius,
and an outer, the ulna; and a distal division, the manus,
made up of the carpus or wrist, and of five digits.
8. The hind-limb, also divisible into three parts: a
proximal, containing a single bone, the femur; a middle,
consisting of a large inner bone, the tibia, and a small
outer one, the fibula; and a distal, the pes, consisting of
the tarsus or ankle, and of four digits.
III. In one of the first half-dozen thoracic vertebre
note:
g. The centrum or body, a sub-trihedral mass of bone
forming the ventral portion of the vertebra.
1o. The neurapophyses or neural processes, paired
bony rods, passing upwards and slightly outwards, one from
each side of the centrum and uniting with one another
264 ZOOTOMY.
above to form the neural arch, through which the spinal
cord passes: each neurapophysis consists of a ventral,
somewhat cylindrical portion, the peduncle, and of a
dorsal flattened portion, the lamina.
11. The neural spine, an elongated, backwardly
directed process proceeding from the apex of the neural
arch at the junction of its two lamin.
12. The transverse processes, short stout rods pro-
ceeding directly outwards one from each side of the neural
arch at the junction of the peduncle and lamina.
13. The anterior zygapophysis, a small horizontal
process projecting forwards from the anterior face of each
neurapophysis at the junction of the peduncle and lamina:
its dorsal surface is flat and smooth, forming an articular
facet.
14. The posterior zygapophysis, a slight projection
of the postero-ventral region of each lamina, bearing an
articular facet on its under side.*
15. In the young skeleton, the epiphyses, two thin
bony disks, closely applied one to the anterior the other to
the posterior face of the centrum to which they are ankylosed
in the adult.
In the young subject the epiphyses easily separate from the vertebra
proper, to which, indeed, they are less firmly attached than to the inter-
vertebral ligaments ($27) ; it therefore often happens, in maceration,
that an epiphysis becomes detached from its own vertebra, but remains
united to the next by the intervertebral ligament.
The free surfaces of the epiphyses are smooth ; their inner surfaces, in
contact with the centrum, are rough, as also are the faces of the centrum
itself: the centrum presents two oblique grooves, corresponding to the
neuro-central sutures (§ 16), and equally well marked whether the latter
1 It is useful to remember that the anterior face of a vertebra can
always be told by observing the zygapophyses : the facets of the anterior
zygapophyses look upwards, inwards, or forwards, those of the posterior
zygapophyses downwards, outwards, or backwards,
THE RABBIT. 265
have disappeared or not; the inner face of the epiphysis bears two
ridges corresponding with these grooves, It is thus easy to tell from the
appearance of a vertebra whether its epiphyses are present or not.
16. The neuro-central sutures, oblique division planes
separating the centrum proper, in the young animal, into
three portions; the middle piece is a distinct bone, the
lateral pieces are continuous with the neurapophyses.
17. The tubercular facet, a small surface near the end
of the transverse process and serving for the articulation of
the tubercle of a rib (§ 29).
18. The capitular demi-facets, two semilunar surfaces
at the junction of the centrum and neurapophysis, one at
the anterior the other at the posterior border of the verte-
bra, and furnished partly by the vertebra proper, partly by
the epiphysis: the anterior demi-facet serves for the articu-
lation of the head of the rib (§ 29) belonging to the vertebra
in question, the posterior for that of the next following rib. .
IV. In the remainder of the vertebral column note:
19. The last three thoracic vertebre: note the
diminished size of the neural spine, which is vertical in the
eleventh (anticlinal vertebra), and slopes slightly forwards
in the twelfth, becoming at the same time compressed from
side to side ; the shortness of the transverse processes, and
the absence of a tubercular facet ; the entire capitular facet
for the head of the rib, there being no half-facet on the
posterior edge of the centrum; the metapophysis, a large
process near the anterior border of the neural arch, just
posterior to the anterior zygapophysis, and projecting
upwards and slightly forwards.
20. The lumbar vertebrz: note the short, forwardly
directed, laterally compressed neural spine; the large
metapophyses; the anterior zygapophyses looking directly
inwards, the posterior outwards; the large transverse
266 ZOOTOMY.
processes increasing in size from the first lumbar vertebra
to the last, and turning forwards; the hypapophysis, a
short flattened process from the under surface of the
centrum of the second and third; and the anapophysis,
a small pointed process, projecting backwards from the
posterior edge of the neural arch beneath the posterior
zygapophysis.
21, The sacral vertebrz: these are much like the
lumbar, but have smaller metapophyses, and no anapo-
physes or hypapophyses. In the first the spine is usualiy
directed forwards, in the second it is vertical, and in the
third and fourth directed backwards. The first and second
only give attachment to the hip-girdle, for which purpose
they are provided with great expanded lateral plates with
roughened edges, which answer to sacral ribs.
22. The caudal vertebre, at first like the sacral, but
gradually diminishing in size and complexity until they are
reduced to mere centra.
23. The last (seventh) cervical vertebra : it somewhat
resembles the anterior thoracic, but the transverse process
has no facet, and the centrum a demi-facet only on its
hinder edge. The centrum also is so altered in shape that
its anterior face looks downwards as well as forwards, and
its posterior face upwards as well as backwards.
24. The third to the sixth cervical vertebrz : these
have the centrum withits anterior face looking downwards and
forwards, and its posterior face upwards and backwards ; the
transverse processes are divided into two parts, one of which
projects directly outwards, while the other (inferior lamina)
forms a flat irregular plate, attached along the whole infero-
lateral edge of the centrum. An aperture, the vertebrar-
terial canal, perforates the base of the transverse process,
and, during life, transmits the vertebral artery (§ 250).
THE RABBIT. 267
25. The second cervical vertebra, or axis ; the centrum
is produced anteriorly into a strong, bluntly-pointed peg,
the odontoid process; on the under surface of this is
an articular surface, and on each side of its base is another
large surface; all these are for articulation with the first
vertebra ; the spine is flattened from side to side, and greatly
produced from before backwards ; the transverse processes
are small, directed backwards, and perforated by the verte-
brarterial canal. In young rabbits (six weeks) this axis
consists of three pieces, one forming the arch, another the
posterior part of the centrum, and the third the anterior
part of the centrum with the odontoid process: the latter
ossification (os odontoideum) answers to part of the
centrum of the atlas.
26. The first cervical vertebra or atlas: the centrum
is reduced to a mere flat plate, hardly thicker than the arch,
and with less than half the antero-posterior dimensions of
the latter; the transverse processes are large, flattened from
above downwards, and perforated; just within and below
the vertebrarterial canal, on the posterior face of the
vertebra, is a large oval facet for articulation with’ the
corresponding surface of the axis, and on the upper sur-
face of the centrum is a smaller facet corresponding to the
surface on the ventral face of the odontoid ; on the anterior
surface are large, paired, irregularly crescentic facets for the
occipital condyles (§ 34).
27. In an entire skeleton note the mode of articulation
of the vertebree: the centra are united by pads of fibro-
cartilage, the intervertebral] ligaments, only to be seen
in the fresh state; the arches are united by the anterior
zygapophysis of any vertebra being overlapped by the
posterior zygapophysis of the vertebra next in front.
28. The intervertebral foramina, seen in the entire
268 ZOOTOMY.
skeleton as spaces between the peduncles of successive
neural arches ; they serve for the transmission of the spinal
nerves.
V. Make out, in the ribs and sternum :
29. The seven true ribs: each consists of a completely
ossified vertebral rib dorsally, and of a cartilaginous
sternal rib ventrally. The vertebral rib has a head
articulating with the capitular facet on the centrum of its
own vertebra and of that next in front; a tubercle on the
dorsal side articulating with the tubercular facet on the
transverse process of its own vertebra, and a short dorsal
process just external to the tubercle. The sternal ribs,
with the exception of the first, sixth, and seventh, articulate
at the junction of two of the segments of the sternum.
30. The five false ribs; in all but the first of these the
tubercle is obsolete, and in all the sternal rib does not
articulate directly with the sternum.
31. The sternum, consisting of six segments, the
so-called sternebre, of which the first is large, and keeled
ventrally, and is called the manubrium. With the sixth is
connected a rounded plate of cartilage, the xiphisternum
or xiphoid process.
VI. In the skull note:
32. The large development of the facial as compared
with the cranial portion of the skull, the latter including
those bones which surround the brain-case.
33. The large foramen magnum, on the posterior
surface of the brain-case, through which the spinal cord
becomes continuous with the brain.
34. The two oval occipital condyles, bounding the
foramen magnum at the sides and below.
35. The large hollow on each side of the skull formed
mainly by the orbit or cavity for the eye, and bounded
THE RABBIT. 269
below by a bony bar, the zygoma: its posterior part
answers to the temporal fossa.
36. The auditory aperture on each side of the hinder
region of the brain-case: it is formed by a sort of bony
tunnel, and looks upwards, outwards, and backwards.
37. The nasal apertures, quite in front of the snout,
and confluent in the dry skull.
38. The very small extent of the bony palate, which
is reduced to a narrow bridge running between the two rows
of grinding teeth (see §§ 65 and 67).
39. The articulation of the lower jaw to the skull directly,
and not through the intermediation of a quadrate bone.
490. The distinctness of most of the bones even in adult
life.
41. The long, slender processes, given off from many of
the bones and helping, in the dry skull, to keep the various
bones together.
42. The basioccipital, a flattened bone, bounding the
foramen magnum below, and forming the hinder part of
the base of the skull and the lower third of. the occipital
condyles.
43. The exoccipitals, joined below with the basi-
occipital, bounding the foramen magnum at the sides,
and forming the upper two-thirds of the occipital condyles.
Each is produced downwards into a paroccipital process,
which fits closely against the posterior surface of the bulla
tympani (§ 54), and is perforated near its junction with
the basioccipital by two small apertures, the condylar
foramina, which transmit the hypoglossal nerve.
44. The supraoccipital, articulated below into the
exoccipitals, and bounding the foramen magnum above : it
is a very irregular bone, with a strongly-pitted surface, and
marked externally by a median, escutcheon-shaped elevation.
270 ZOOTOMY.
In the adult, the basi-, ex-, and supraoccipitals are all
fused together into the single occipital bone.
45. The interparietal, a small transversely oval bone,
interposed between the middle part of the front edge of the
supraoccipital and the parietals (§ 46).
46. The parietals, a pair of thin, slightly arched bones,
forming a considerable part of the roof of the brain-case :
they are separated from one another by the median sagittal
suture, and from the interparietal and supraoccipital, with
which they articulate posteriorly, by the transverse lamb-
doidal suture: the outer edge of each gives off a long
downwardly directed process, which, in the entire skull, is
covered by the squamosal (§ 53).
47. The frontals, roofing in the anterior part of the
brain-case, articulated with one another in the middle line
by the frontal suture, and with the parietals behind by
the transverse coronal suture. Each is an irregular bone,
with a slightly arched upper surface; an irregular anterior
border ; an orbital process, a thin plate continued down-
wards and inwards from its outer border, and forming the
upper part of the inner wall of the orbit; and a supra-
orbital process, projecting directly outwards from the
outer border, free at both ends, and forming a protection to
the orbit above.
48. The basisphenoid, articulated behind by a broad
surface with the basioccipital, and tapering in front to a
blunt point; it is perforated at about the middle of its
extent by an oval foramen, and its upper surface is hollowed
out to form the sella turcica, which lodges the pituitary
body (§ 484), and is bounded before and behind by the
anterior and posterior clinoid processes, of which
the latter only are formed by the basisphenoid.
49. The alisphenoids: two wing-like bones directed
THE RABBIT. 271
upwards and outwards, firmly ankylosed, even in young
rabbits, one to either side of the basisphenoid, and pro-
duced below on each side into two lamin, which unite
with one another along their anterior edges, forming a
dihedral angle open behind. These form the pterygoid
process of the alisphenoid: with the inner lamina the
pterygoid bone (§ 68) articulates.
50. The sphenoidal fissure, a large notch on each side
between the basisphenoid and alisphenoid; it transmits
the third, fourth, and sixth nerves, as well as the first and
second divisions of the fifth.
51. The presphenoid, a laterally compressed bone,
joined behind to the basisphenoid by synchondrosis (carti-
laginous union), so that in the dry skull there is always a
considerable interval between the two bones. It forms the
inferior and anterior boundary of a large oval aperture
which puts the two orbits in communication with one
another, and both in communication with the brain-
case: this is the optic foramen, and transmits the
optic nerves (§ 485). On its upper or cranial surface the
presphenoid is produced behind into the two anterior
clinoid processes: in front of the optic foramen it gives
off two irregular outwardly diverging laminz, which form
part of the inner wall of the orbit, articulating above
with the inferior border of the orbital process of the frontal.
52. The orbitosphenoids: two winglike lamin
directed outwards and slightly backwards, projecting one
from each side of, and completely ankylosed with, the pre
sphenoid: they form the superior and posterior boundary
of the optic foramen.
53. The squamosal: a bone of very irregular form,
articulating above with the parietal and frontal, in front
with the orbital process of the frontal and the orbito-
272 ZOOTOMY.
sphenoid, below with the alisphenoid, and behind with
the descending process of the parietal. From its outer
face is given off the zygomatic process, a strong bar
of bone which passes first outwards, then downwards, and
lastly forwards, and which bears on the under surface of
its outwardly directed portion an articular surface—the
glenoid cavity—for the lower jaw. From the posterior
edge of the squamosal a slender process is given off, which
passes backwards and downwards against the surface of the
periotic (§ 56).
54. The tympanic, a bone constituting the osseous
part of the auditory meatus. It consists of a tubular
portion above, and of a swollen portion below, which
projects on the under surface of the skull and articu-
lates with the lateral edge of the basioccipital: this last
is the bulla tympani. Both tubular and _ bulbous
portions are incomplete on the inner face, a vacuity being
left which is only filled up when the tympanic bone is
applied against the periotic. At the junction of the
tubular and bulbous portions the tympanic is produced on
its inner surface into a curved flattened ridge, to which the
tympanic membrane is attached (§ 346).
55. On the posterior border of the tympanic, at the
junction of its tubular and bulbous portions is a shallow
groove: when the tympanic is in place this notch is con-
verted by the periotic into a canal, the stylo-mastoid
foramen, which transmits the seventh nerve. A notch in
the postero-inferior region of the bone is also converted
into a canal by the juxtaposition of the periotic, forming the
bony portion of the Eustachian tube (§ 351).
56. The periotic: a very irregular bone, articulating
with the exoccipital behind, the supraoccipital above, the
descending process of the parietal in front, and the basi-
THE RABBIT. 273
occipital below: the tympanic is closely applied to its outer
surface, the tympanic cavity being enclosed between the
two bones: a process from its posterior edge fits over the
groove just noticed in the tympanic, completing the stylo-
mastoid foramen and helping to keep the two bones in
position. On its outer surface, and therefore seen only
when the tympanic is removed, are two small apertures, the
anterior of which is the fenestra rotunda, the posterior
the fenestra ovalis. On its inner or cranial surface
is a large hemispherical depression, the floccular fossa,
for the lodgment of the flocculus of the cerebellum (§ 477),
and beneath this is a shallow depression, the internal
auditory meatus, with two apertures in it for the trans-
mission of the seventh and eighth nerves (§§ 491, 492).
57. The foramen lacerum medium: a large space
between the periotic and alisphenoid : it transmits the third
division of the fifth nerve (§ 357).
58. The foramen lacerum posterius: a space
between the periotic and the exoccipital, through which the
ninth, tenth, and eleventh nerves leave the skull (§ 493).
59. The mesethmoid: this is seen only in the dis-
articulated or bisected skull: it consists of two parts, the
cribriform plate, riddled with numerous small holes for
the passage of the olfactory nerves, and completing the
antero-inferior portion of the wall of the brain-case, and
of the lamina perpendicularis, a median vertical plate,
which proceeds from the anterior surface of the cribriform
plate into the nasal cavity. In the recent state the lamina
perpendicularis is continued forwards by a cartilaginous
plate, the septum nasi, and the two together separate the
right and left nasal cavities from one another.
60. Lying against the ventral border of the septum nasi are the
paired scroll-like Jacobson’s cartilages: they are attached in
i T
274 ZOOTOMY.
front to the septum and free behind, and are ensheathed in
the palatine processes of the premaxille. The dorsal edge of the
septum is produced on each side into a long, narrow, horizontal shelf,
which underlies the nasal, and is continued in front into a narrow ali-
nasal cartilage, which encircles the nostril and unites below with the
antero-ventral region of the septum.
61. The parethmoids, or ethmo-turbinals, two
complicated folded bones, situated one on either side of the
mesethmoid, to which they are ankylosed in the adult.
62. The vomer, a long bone, deeply grooved on its
upper surface, the groove receiving the inferior edge of
the lamina perpendicularis and septum nasi; in the adult
it is ankylosed to the parethmoids.
63. The nasals, two large flat bones which roof in the
nasal cavities, articulating with one another in the middle
line, and with the frontals behind. The inferior surface of
each nasal is produced into a very thin, pouch-like process
of bone, the naso-turbinal.
64. The premaxille, a pair of irregular bones which
form the anterior boundary of the snout. Each gives off a
long nasal process from its upper and posterior edge,
which passes backwards and slightly upwards, articulating
with the external border of the nasal and with the anterior
edge of the frontal; a palatine process from its inner
and anterior region, which passes directly backwards, in
contact with its fellow of the opposite side along the
palate ; and a short, stout maxillary process, which passes
directly backwards from its postero-ventral region and
articulates with the maxilla in the premaxillo-maxillary
suture; and presents, in its antero-inferior region, two
sockets or alveoli for the incisor teeth (§ 77).
65. The maxille, two large and very irregular bones,
which, together with the premaxilla, form the framework of
the upper jaw. Their outer surfaces are spongy ; on their
THE RABBIT, 278
ventral surfaces are the alveoli for the premolar and molar
teeth (§§ 79 and 80); the inner and inferior edge of each
gives off, opposite the first and second premolar teeth, a
horizontal palatine process, which, articulating with its
fellow of the opposite side, forms the anterior half of the
bony palate. From the outer and posterior region of each a
strong process is given off, which turns first outwards and
then backwards, its upper edge articulating with the lower
edge of the zygomatic process of the squamosal; in the
new-born rabbit this process is a separate bone, the jugal
or malar. A little above the first premolar tooth (§ 79) is
an aperture, the infra-orbital foramen, leading by a
canal into the orbit, and transmitting the second division
of the fifth nerve (§ 358).
66. The maxillo-turbinals, two thin scroll-like bones,
which occupy the anterior portion of the nasal chamber.
67. The palatines, thin laminze of bone, which articulate
in front with the maxillz, above with the orbital processes
of the presphenoid, and behind with the pterygoid and
with the pterygoid process of the alisphenoid. From the
inner and anterior region of each is given off, opposite
the third premolar tooth, a horizontal, inwardly directed
palatine process, which, articulating in the middle line
with its fellow of the opposite side, and in front with the
palatine process of the maxilla, forms the posterior half of
the bony palate.
68. The pterygoid, a small, irregular plate of bone,
articulating with the posterior edge of the palatine and with
the inner lamina of the pterygoid process of the alisphenoid
(§ 49): it ends ventrally in the free, backwardly curved
hamular process.
69. The lacrymals, two small bones fitted, one on
each side, into the .anterior wall of the orbit, between the
T2
276 ZOOTOMY.
maxilla and frontal: they often fall out in the dry skull.
Each is perforated, near its outer border, by a small aperture
for the lacrymal canal.
70. In the longitudinal section of the skull note the
cranial fossze for the reception of the chief divisions of
the brain. The hindmost of these, or cerebellar fossa,
for the lodgment of the cercbellum (§ 477), is marked off
from the cerebral fossa, for the cerebral hemispheres
(§ 480), by a sharp oblique ridge along the inner face of
the periotic and by the junction of the parietal and supra-
occipital ; it is along this line that the tentorium (§ 162) is
attached. The small olfactory fossa, for the olfactory
lobes (§ 483), is an offshoot of the anterior end of the
cerebral, and is marked only by an inconspicuous ridge on
the inner surface of the frontal.
71. The mandible, or lower jaw, consisting of two
separate halves, or rami, which articulate with one another
in front by a rough surface. Each ramus consists of a
horizontal portion, bearing the sockets for the teeth, and of an
ascending portion, which ends above in the longitudinally
elongated condyle for articulation with the squamosal.
Anteriorly the ascending portion gives off the plate-like,
slightly incurved coronoid process. ‘The postero-inferior
portion, or angle of each ramus, is somewhat produced
backwards, and gives off an inward shelf-like projection,
On the inner surface of each ramus, at the junction of the
horizontal and ascending portions, is the inferior dental
foramen, consisting of a number of small apertures and
transmitting the third division of the fifth nerve (§ 357)-
Interpored between the condyle and the glenoid cavity is a concavo-
convex plate of cartilage, the meniscus,
72, The hyoid, situated at the root of the tongue,
THE RABBIT. 277
anterior to the larynx (see §§ 124, 125, p. 289), and always
detached in the prepared skull: it consists of a stout thick
body, or basi-hyal, a pair of small anterior cornua, or
cerato-hyals, and a pair of long, backwardly directed
posterior cornua, or thyro-hyals (cerato-branchials).
VII. Carefully break away in an entire skull the outer
wall of the tympanic bone, and make out the
following bones: }
73. The malleus, a small bone, recognised at once by
the bony process or manubrium, by which it is attached,
in the recent state, to the tympanic membrane. It con-
sists of a rounded head, from which the manubrium and
other lesser processes are given off, and which presents
a saddle-shaped surface for articulation with the incus.
74. The incus, articulating by a saddle-shaped surface
with the malleus, and giving off two processes, the short
crus and the long crus.
75. The os orbiculare, a minute disk of bone attached
to the long crus of the incus.
76. The stapes, a stirrup-shaped bone, having its base
inserted into the fenestra ovalis (§ 56), and articulated by
a small knob on the summit of its arch to the orbiculare.
VIII. Observe the following points in the teeth :
77. The incisors, of which two are situated in each
premaxilla, and one in each ramus of the mandible. The
anterior upper incisors are long, curved, chisel-shaped
teeth, covered with enamel on the anterior surface only,
marked on the same surface with a deep longitudinal groove,
and destitute of roots. The posterior upper incisors are
small teeth, situated behind the corresponding anterior
incisors. The lower incisors resemble the anterior upper
1 This may be conveniently done with the skull of ‘a specimen used
for dissection. See Secs, XLII—XLIII. p. 331.
278 ZOOTOMY.
incisors, except that they are not grooved anteriorly. In
the position of rest they fit against the posterior upper
incisors.
78. The absence of canines, or teeth situated imme-
diately behind the premaxillo-maxillary suture.
79. The premolars: three on each side of the upper
jaw (in the maxilla), two on each side of the lower jaw, and
separated by a long interval or diastema from the incisors.
They are long curved teeth, devoid of fangs. The first
tooth in the upper jaw is small and quite simple: the
remaining two are marked externally with a longitudinal
groove, separating two well-marked ridges: their crowns
present two transverse grooves bounded by ridges. In the
lower jaw the first premolar has two grooves and three
ridges, the second resembles those of the upper jaw.
80. The molars, three on each side of each jaw, and
closely resembling the upper premolars, except that the last
in each jaw is small and simple.
1X. In the shoulder-girdle and fore-limb note :
81. The scapula, a flat triangular bone, lying, in the
natural position, external to the anterior ribs, its apex being
over against the first rib, and the long axis, drawn from its
apex to its base, inclined upwards and backwards. The
base of the triangle consists, in the recent state, of a strip
of cartilage, the supra-scapula ; its apex is formed by the
smooth concave glenoid cavity for the articulation of
the humerus: immediately anterior to this latter is a small
inwardly curved coracoid process, consisting in the
young animal (six weeks) of two separate ossifications and
representing the coracoid of the lower Vertebrata: of
these ossifications the pre-axial goes mainly to form the
coracoid process, the post-axial is a small nodule bearing a
facet which forms the anterior part of the glenoid cavity.
THE RABBIT. 299
The anterior or pre-axial edge of the scapula is the
coracoid border, its post-axial edge the glenoid border ;
a third or acromial border is constituted by the free
edge of the large spine which projects from its external
face; a fourth or supra-scapular border by its dorsal
edge. Its external surface prescuts a pre-scapular fossa
anterior to, and a post-scapular fossa posterior to, the
spine: its internal surface constitutes the sub-scapular
fossa. The free ventral end of the spine is the acro-
mion ; a small process, which projects from it backwards
and downwards, is the metacromion.
82. The clavicle, a small, curved, rod-like bone, attached
by fibrous tissue at one end to the sternum, at the other to
the acromion.
Attached to the outer end of the clavicle is a small nodule of cartilage,
the meso-scapular segment: attached to its inner or sternal end are
two similar nodules, that nearest the clavicle is the procoracoid,
the other the omosternum.
83. If the fore-limb be compared with that of a Lizard
(p. 147 § X.), it will be seen that the altered position of
the parts in the mammal is due to the following changes :}
(1) the distal end of the humerus has become rotated
backwards so as to bring the whole limb into a plane parallel
with the median vertical plane of the body; the pre-axial
_, border then becomes external, and the originally dorsal
surface looks, on the whole, backwards: (2) the radius
and ulna have become fixed in the position of pronation,
that is, the distal end of the radius has rotated round the
ulna carrying the hand with it: the consequence of this is
that while the pre-axial border of the proximal end of the
1 The changes in position of the vertebrate limbs are best made out
on the skeleton of a man or ape, in which the bones are articulated so
as to allow cf the natural movements, including pronation and supina-
tion, being performed. See Flower, Osteology of the Mammalia, p. 245.
280 ZOOTOMY.
fore-arm is, like that of the humerus, external, the same
border comes to be internal in the distal end of the fore-arm
and in the manus, the dorsal surfaces of which look, on the
whole, forwards.
84. The humerus, a long bone consisting of a shaft
and of two prominent extremities, and having its long
axis directed from the glenoid cavity downwards and back-
wards, so that its originally dorsal surface looks upwards and_
backwards, its ventral surface downwards and forwards, its
pre-axial border outwards, and its post-axial border inwards.
The proximal extremity presents, dorsally, a rounded head
for articulation with the glenoid cavity; pre-axially, a large
projection, the greater tuberosity ; post-axially, a smaller
projection, the lesser tuberosity; and between the
tuberosities a depression, the bicipital groove. On the
anterior (ventral) surface of the proximal end of the shaft is
the deltoid ridge. The distal extremity presents a large
pulley-like surface, or trochlea, for the articulation of the
ulna and radius, and a smaller pre-axial surface, or capi-
tellum, for the radius only (see §§ 85 and 86) ; a deep
olecranon fossa on the posterior (dorsal) side, for the
reception of the olecranon process of the ulna, perforated
by a small supra-trochlear foramen ; a small pre-axial
external condyle just outside the capitellum; and a
larger post-axial internal condyle, similarly situated with
regard to the trochlea. In the young rabbit the extremities
of the humerus consist of separate bones, or epiphyses.
85. The radius, or shorter bone of the fore-arm, slightly
curved forwards, and so situated that its true dorsal surface
looks forwards and_ slightly upwards, and its pre-axial
border inwards. Its proximal extremity or head presents
a double articular surface for the pulleys of the humerus:
its distal extremity, a pair of slight concavities for the
THE RABBIT. 281
scaphoid and lunar bones (§ 87): the ventral (posterior)
surface of the shaft is flattened, and fits against the
ulna. In the young animal both extremities consist of
epiphyses.
86. The ulna, or longer bone of the fore-arm: it is
immovably articulated, though not ankylosed, to the radius,
in the position of pronation, its anterior surface being
flattened for the reception of that bone. At the proximal
end of the same surface is the sigmoid cavity for the
articulation of the humerus: beyond this the bone is pro-
duced into the olecranon or anconeal process. At its
distal end the ulna presents a convex surface for the
articulation of the cuneiform (§ 87). Inthe young animal
the whole distal end of the bone is formed of an epiphysis:
the proximal epiphysis is small, consisting of a nodule on
the olecranon.
87. The carpus, consisting of a proximal and a distal
row of small nodular bones. The bones.of the proximal
row, beginning from the pre-axial (inner) side, are sca-
phoid (radiale), and lunar (intermedium), articulating
with the radius, cuneiform (ulnare), articulating with the
ulna, and pisiform (a sesamoid), articulating with the
ventral (palmar) side of the cuneiform and with the ulna.
In the distal row are five bones, the central one of which
is distinctly proximal to the other four, and really con-
stitutes by itself a middle row; this. is the centrale,
the others being trapezium (carpale 1), on the pre-axial
side, then trapezoid (carpale 2), magnum (carpale 3)
situated immediately to the post-axial side of the centrale,
and unciform (carpalia 4 and 5) on the post-axial side.
88. The metacarpus, consisting of the five meta-
carpal bones, of which that belonging to the first or pre-
axial digit (pollex) is the shortest, the fifth somewhat longer,
282 ZOOTOMY.
the second and fourth still longer, and the third longest of
all. The first articulates with the trapezium, the second
with the trapezium, trapezoid, centrale, and magnum, the
third with the magnum and unciform, and the fourth
and fifth with the unciform. Their distal ends present
pulley-like surfaces for articulation with the proximal pha-
langes, and in the young animal are formed by epiphyses:
they have no proximal epiphyses.
89. The phalanges, of which there are two to the
pre-axial digit, or pollex, and three to the other four. The
proximal and middle phalanges have hollowed proximal
and pulley-like distal articular surfaces; the distal or ungual
phalanges have hollowed proximal surfaces, and have a
conical form, the dorsal surface being grooved for the firmer
attachment of the horny claw. In the young rabbit the
proximal end of the proximal and middle phalanges are
formed by epiphyses: they have no distal epiphyses.
go. The sesamoid bones, small nodular ossicles situated on the
palmar side of the joints of the digits: there is a pair between the
metacarpal and proximal phalanx, and a single one between the middle
and distal phalanges of all the digits except the first ; and one between
the proximal and distal phalanges of the pollex.
X. In the hip-girdle and hind limb note:
gt. The pelvis, or hip-girdle, consisting of the two
innominate bones. Each of these consists of an
antero-dorsal portion, the ilium, articulated by a rough
surface to the sacrum, and of a postero-ventral portion
perforated by a large aperture, the obturator foramen,
which divides it into a pre-axial (anterior) part, the pubis,
and a post-axial (posterior) part, the ischium. In the young
animal the ilium, ischium, and pubis are separate bones
meeting one another in a triradiate suture in the centre of
THE RABBIT. 283
the acetabulum,! a deeply concave articular surface on
the external face of the innominate bone. The ilium
presents a ventral (pre-axial) pubic border, a dorsal
(post-axial) ischial border, an external acetabular
border consisting of an inconspicuous ridge running from
the acetabulum along its outer surface, and an anterior
(dorsal) supra-iliac border along its free end: that portion
of its external surface on the ventral side of the acetabular
border is the iliac fossa, that on its dorsal side the
gluteal fossa; its inner surface is the sacral fossa.
The pubes of opposite sides unite with one another in
the middle line, by synchondrosis, to form the symphysis
pubis: the posterior part of the ischium is expanded and
roughened, forming its tuberosity (tuber ischii).
g2. If the hind-limb be compared with that of the Lizard
(p. 151 § 108), it will be seen that the femur, and with it
the whole limb, has undergone rotation forwards: as a con-
sequence of this the hindlimb is, like the fore-limb,
brought into a plane parallel. with the median vertical plane
of the body, but, the rotation being in the opposite direc-
tion, the pre-axial border is internal in the whole limb, and
the originally dorsal surface looks, on the v-hole, forwards.
93. The femur, the long axis of which, in the natural
position, is directed downwards and: forwards, so that its
originally dorsal surface looks upwards and forwards, and its
pre-axial border inwards. Its proximal extremity presents
a rounded, projecting head on its pre-axial (inner) border,
for articulation with the acetabulum; a large process, the
greater trochanter, just external to the head; a pit, the
trochanteric fossa, on the ventral surface, bounded
pre-axially by the great trochanter; a lesser trochanter
1 The pubis proper is really shut out from the acetabulum by a small
epiphysis, the cotyloid bone.
234 ZOOTOMY.
on the pre-axial border, immediately distal to the head ;
and a small third trochanter on the post-axial (external)
border, slightly beyond the great trochanter. On the head
is a shallow pit for the attachment of the ligamentum
teres (§ 471). Its distal extremity presents an internal
condyle (pre-axial) and an external condyle (post-
axial), separated from one another by the intercondylar
notch, which, with the condyles, forms the articular surface
for the tibia (§ 96) and patella (§ 95). The internal and
external tuberosities are small roughened projections,
situated, the first on the pre-axial, the second on the
post-axial, border of the distal extremity of the femur,
close to the condyles. In the young animal the whole
distal end of the femur is formed by an epiphysis, while at
the proximal end are two epiphyses, one forming the head,
the other the greater trochanter.
94. Two nodular sesamoid bones, or fabelle, occur in
connection with the distal end of the femur, a smaller pre-
axial, and a larger post-axial, both being situated quite on the
posterior (ventral) aspect of the bone.
95. The patella (a sesamoid), a small nodule of bone,
fitting against the pre-axial end of the intercondylar notch,
and connected by ligament to the tibia.
96. The tibia, or larger bone of the shank, so placed
that its true dorsal surface looks forwards and slightly down-
wards, and its pre-axial border inwards. Its proximal ex-
tremity presents two slightly concave articular surfaces
for the condyle of the femur, and two roughened tuberosities
on its pre-axial and post-axial borders respectively. A
prominent ridge, the crest of the tibia, extends along the
proximal end of the (anterior) dorsal surface of the bone.
Its distal extremity presents two articular surfaces, one
pre-axial, and pulley-like, for the astragalus, the other post-
THE RABBIT, 285
axial, somewhat flattened, and projecting beyond the first,
for the calcaneum (§ 99).
97. The femoro-tibial or semilunar cartilages, two thin plates
interposed between the femur and the tibia: their concave edges are
turned towards one another, and they are situated immediately beneath
the condyles of the femur,
98. The fibula, a small rod of bone, attached by its
proximal end to the outer tuberosity of the tibia; distally
it fuses with the tibia at the middle of its length ; its proxi-
mal end is formed by an epiphysis.
g9. The tarsus, consisting of six irregular bones
arranged in three rows. In the proximal row are two bones,
the astragalus (tibiale), situated on the pre-axial side, and
having at its proximal end a large pulley-like surface for
articulation with the tibia ; and the calcaneum (fibulare), on
the post-axial side, having at about the middle of its length
an articular surface for the tibia, beyond which it is pro-
duced into the long calcaneal process, or heel. In the
middle row is the single navicular (centrale), articulating
chiefly with the distal end of the astragalus, but partly also
with the distal and pre-axial edge of the calcaneum ; its
ventral or plantar surface is produced into a large distally
directed process. In the distal row are three bones, the
mesocuneiform (tarsale 2) and ectocuneiform (tarsale
3), articulating with the navicular, and the cuboid (tarsalia
4 and 5), articulating chiefly with the calcaneum. The
entocuneiform (tarsale 1), is either absent or is ankylosed
with the proximal end of the second metatarsal (see § 100).
100. The metatarsals, four in number, the first (that of
the hallux or pre-axial digit) being absent. The third is
the longest, the fourth the next longest, and the second and
fifth of about the same length. The proximal end of the
second (the apparent first) articulates with the mesocuneiform,
286 ZOOTOMY.
and is produced into a process which passes external to the
latter, and articulates with the navicular; this process is a
separate bone in the young rabbit, and may represent the
entocuneiform. The second metatarsal articulates with the
ectocuneiform, the third and fourth with the cuboid : all four
are in close contact with one another at their proximal ends:
their distal ends are pulley-shaped.
ror. The phalanges, of which each digit has three:
they have the same characters as those of the manus (§ 89.
p. 282).
102. The sesamoid bones of the pes are similarly situated to those
of the manus.
B.—DIRECTIONS FOR DISSECTION.
XI. Make out the external characters as follows:
103. The hairy integument, which invests the body,
the hairs extending even over the tip of the nose and the
walking surfaces of the feet.
to4. The division of the body into head, trunk, and
limbs: the union of the head and trunk by a distinct
though short neck: the short tail.
105. The division of the head into a hinder cranial
portion containing the brain, and an anterior facial
portion or snout.
106, The external nostrils or anterior nares, oblique
slits at the fore end of the snout, connected by a median
hairless groove with the mouth.
107. The mouth, a small transverse aperture bounded by
the upper and lower lips ; the hairy integument stops at the
edges of these above and below, while at the sides it is con-
tinued for a considerable distance into the cavity of the mouth.
108. The vibrissze, or “ whiskers,” a number of long
stout bristles on the upper lip.
THE RABBIT. 287
10g. The large eyes, guarded by an upper and a lower
eyelid, and by a third eyelid or nictitating membrane,
which can be pulled over the eye from its anterior (inner)
corner, and is strengthened by a plate of cartilage.
tro, The auditory apertures, one on either side of the
hinder region of the head, guarded by the large external
ears.
111. The two rami of the mandible can be felt through
the skin, and, between their hinder ends, the movable
larynx (§ 124).
112. The vertebral column can be felt extending
from just behind the head to the extremity of the tail.
113. At the sides of the anterior part of the trunk, the
ribs can be felt through the skin, and along the middle
ventral line of the same region the breast-bone or sternum.
These, with the corresponding part of the vertebral column,
enclose the anterior or thoracic region of the trunk.
x14. The posterior or abdominal region of the trunk,
enclosed at the sides and below only by skin and muscle,
except at its posterior extremity, where it is bounded by the
pelvis, the ventral portion of which, or symphysis
pubis, can be readily felt through the skin.
115. The anus, a rounded aperture just under the root
of the tail, and bounded laterally by two naked patches
of integument, the perineal spaces, on which open
the ducts of the perineal glands (see § 277), to the
secretion of which the animal owes its peculiar and unpleasant
smell.
116. The urinogenital aperture, between the anus and
the symphysis pubis: in the male it is small and situated at
the extremity of the backwardly directed intromittent organ
or penis, in the female it is a large slit-like opening
or vulva.
288 ZOOTOMY.
117. In the adult male, a pair of considerable projections
will be seen, one on either side of the root of the: penis ;
these are the scrotal sacs, and contain the testes.
118. The scapula, a large bone, attached to the rest of
the skeleton only by muscle, can be felt through the skin in
the antero-dorsal region of each side of the thorax.
119. The division of the fore-limb into upper-arm
or brachium (almost hidden by the skin), fore-arm or
antebrachium, and hand or manus, the latter provided
with five clawed digits : of these the innermost or pre-axial
digit is distinguished as the thumb or pollex.
120. The division of the hind-limb into thigh or
femur (almost hidden in the skin), shank or crus, and
foot or pes, the latter very long, and terminated by four
clawed digits: the innermost of these corresponds with the
index, the true first digit or hallux being absent.
121. In the female, the teats of the four or five pairs of
mammary glands are seen, about two inches apart, on
either side of the middle ventral line of the body: the
anterior pair is thoracic, and occurs at about the junc-
tion of the anterior and middle thirds of the thorax: the
remaining three pairs are abdominal in position.
XII. Fix the animal in the supine position, “2, with
the ventral surface upwards ; make a longitudinal
incision into the skin over the sternum, and
continue the cut forwards to the mandibular
symphysis and backwards to the pubic symphysis.
With the handle of a scalpel, carefully separate
the skin from the underlying parts over the whole
ventral surface. Note;
122, A thin sheet of muscle—the panniculus car-
nosus, or cutaneous muscle—lying immediately beneath
the skin, to which it is closely attached, and covering the
THE RABBIT. 289
whole ventral surface of the trunk and neck; it is readily
distinguished from the skin by containing numerous blood-
vessels. In all probability it will be removed with the skin,
if not, it should be dissected off separately.
The cervical portion of the panniculus is called the platysma
myoides : the fibres of its thoracic portion are gathered into a strong
bundle, which becomes tendinous and is inserted into the shaft of the
humerus at its proximal end.
123. In the adult female, the mammary glands,
large, irregular, whitish masses, situated between the skin
and the underlying muscles, and opening externally by
the teats.
124. The trachea, or windpipe, in the middle line of the
neck, known by its regularly arranged cartilaginous cings ;
it ends in front in the larynx, which is situated in the hinder
end of the triangular space inclosed by the two rami of the
mandible: to see these and the following structures clearly
the cervical portion of the cutaneous muscle should be
carefully dissected away.
125. A median mass of muscle (mylohyoid, &c.)
situated just anterior to the larynx and between the anterior
ends of the mandibular rami: in it the hyoid bone is
embedded ; the posterior cornua ($72) emerge from its
hinder border and pass backwards and outwards towards
the larynx.
126. The submaxillary (salivary) glands, reddish,
ovoidal bodies, about one-third inch in length, situated one
on either side of the middle line, somewhat anterior to the
larynx.
127. The external jugular veins, large vessels, usually
gorged with blood after death, lying one on either side of
the trachea.
U
290 ZOOTOMY.
128. The sternum, a bony bar in the middle line of the
chest, ending behind in a large discoidal cartilage, the
xiphoid process.
129. The small, incompletely ossified clavicles, pass-
ing each from the upper extremity of the sternum to the
corresponding shoulder.
130. The sterno-mastoid, a long slender muscle,
arising in conjunction with its fellow of the opposite side
from the anterior end of the sternum, and passing obliquely
forwards and outwards to the skull, just internal to the ex-
ternal jugular vein.
131. The pectoralis major, a large muscle, covering
the ventral wall of the thorax: its fibres pass from the side
of the sternum upwards and outwards to the upper arm.
The fibres of the pectoralis major pass either directly cutwards, or, in
the posterior part of the muscle, outwards and forwards, and are
gathered into a strong bundle which is inserted into the deltoid ridge of
the humerus.
132. The pectoralis tenuis, a thin sheet of transverse fibres cover-
ing the anterior part of the pectoralis major.
133. The pectoralis minor, seen by removing the pectoralis major
and tenuis: it is a triangular muscle arising from the sternum, and
inserted partly into the clavicle, partly into the scapula (see § 4o1).
134. The ribs, largely concealed by the pectoral
muscles ; each consists of a bony portion (vertebral rib)
attached to the vertebral column, and of a cartilaginous
portion (sternal rib), attached to the sternum: they are
best seen by removal of the pectoral muscles.
135. The external intercostal muscles, short fibres
filling up the interspaces between successive ribs: they are
very transparent in the fresh subject, allowing the pink
lungs to be seen through them.
136. The blood-vessels and nerves of the arm,
THE RABBIT. 291
passing from the thorax dorsal to (beneath in the present
position) the pectoral muscles, outwards to the arm.
137. The linea alba, a faint band of fibrous tissue, more
opaque than the general muscular walls of the body, passing
from the posterior extremity of the sternum to the symphysis
pubis.
138. The rectus abdominis, a band-like area of
muscle lying on either side of the linea alba: its fibres run
longitudinally.
139. The external oblique muscle, just external to the
rectus; its fibres run from above downwards and backwards.
140. The internal oblique, seen by dissecting away part of the
external oblique, which it immediately underlies : its fibres run down-
wards and forwards, crossing those of the external oblique.
141. The transversalis, seen by dis-ecting away a portion of both
external and internal oblique : it lies between the latter and the peritu-
neum (§ 148), its fibres running nearly parallel to those of the external
oblique.
142. Poupart’s ligament, a fibrous cord passing on
each side from the symphysis pubis upwards and forwards
to the anterior part of the ilium (§ 91).
143. The blood-vessels and nerves of the legs,
passing from the abdominal cavity, beneath Poupart’s liga-
ment, outwards to the leg.
144. The abdominal viscera are seen, especially in
young subjects, through the thin abdominal walls,
XIII. Make an incision down the linea alba, from the
xiphoid process to the symphysis pubis: from the
anterior extremity of this, make transverse in-
cisions, and turn back the flaps of muscle.
Without disturbing anything, note in the abdo-
minal cavity thus laid open:
145. The peritoneum, a moist shining membrane,
lining the whole abdominal cavity.
U2
292 ZOOTOMY. —
146. The diaphragm, a thin membrane, partly muscular,
partly fibrous, which forms the anterior wall of the cavity :
through its transparent central portion will be seen the pink
lungs.
147. The large, dark-red liver, made up of several lobes,
and situated immediately posterior to the diaphragm.
148. The smooth-walled, bluish-white stomach, partly
covered by the liver: its more dilated (cardiac) end is seen
to lie towards the animal’s left side.
149. The reddish coils of the small intestine, some of
which are seen at the anterior, others at the posterior part
of the abdominal cavity.
150. In about the posterior two-thirds of the cavity are seen
(usually) three folds of the enormous czecum or blind gut,
known by its olive-green colour, the spiral constriction en-
circling it, and the fact of its diameter being many times
greater than that of the small intestine.
151. The colon, usually situated between two folds of the
ceecum, with which it is seen to be connected, and which it
resembles in colour ; its diameter is less than that of the
cecum, and its walls are sacculated.
152. In the hinder end of the cavity, as well as in its
right anterior corner, are usually to be seen portions of the
rectum, which is of a light brownish colour, and contains
pill-like masses of black feecal matter.
153. Quite at the posterior end of the cavity is seen the
urinary bladder, the amount visible of which varies
greatly according to its state of distension
154. In a male specimen the scrotal sacs, hanging
down from the abdominal cavity, one on each side of the
penis.
155. By turning aside the intestines, the kidneys (§§ 187,
196) are seen attached to the dorsal wall of the abdomen.
THE RABBIT. 293
156, In the female the uteri (§ 288) and ovaries (§ 291)
are seen when the intestines are turned aside: they are in-
conspicuous structures in young individuals, but very obvious
in adults.
XIV. Make a small aperture in one side of the
diaphragm—say the left—and note the immediate
collapse of the left lung. Dissect away the
pectoral muscles, cut through all the vertebral
ribs of the left side, except the last five, at about
a quarter of an inch from their junction with
the sternal ribs: from the posterior end of
the incision thus made, cut downwards (z.¢. to-
wards the sternum) for about an inch, and
then forwards, cutting through the sternal ribs:
turn forwards the flap thus separated, and carefully
dissect it away from the underlying tissues at its
anterior end, so as to detach it altogether without
injuring the jugular and brachial veins: proceed
in the same way on the right side, noting that the
right lung, like the left, does not collapse as long
as the thoracic walls of its own side are intact.
Note in the thoracic cavity thus laid open:
157. The small size of the thoracic as compared with
the abdominal cavity: this is usually the case in herbivorous
animals.
158. The heart, adark-red, conical body in the centre of
the thoracic cavity, and enclosed in a thin membrane, the
pericardium: its broad base is turned forwards, its
blunt apex points backwards and somewhat to the left
side.
159. The thymus gland, a soft, fat-like body, anterior
to, and partly hiding the base of, the heart. It is especially
large in young animals.
294 ZOOTOMY.
160. The lungs, spongy bodies of a light pirk colour,
situated one on either side of the heart. ‘They will be, by
the pressure of the air on their outer surfaces, completely
collapsed: to see their actual shape and relations they
should be inflated from the tiachea, by making a small
aperture in it and inserting a blowpipe.
161. The pleura, a shining membrane lining the thorax
and forming a double median vertical partition—the medi-
astinum—which divides the thorax into right and left
pleural cavities, in each of which a lung is contained :
the mediastium is seen in the space between the pericardium
and the sternum (see § 222).
AV. Place the animal in the prone position, z.e. with the
dorsal surface upwards, first pinning together the
reflected abdominal walls to keep the viscera in
position : make a median incision through the skin
from the snout to about the middle of the thoracic
region, and dissect away the skin from the whole
dorsal surface of the head and neck. Dissect
away the muscle from the anterior region of
the neck and posterior region of the head, and
find the occipito-atlantal articulation, or
place where the skull articulates with the vertebral
column. Cut through the occipito-atlantal
membrane, which will be seen stretching between
the supraoccipital and the arch of the atlas:
the anterior end of the spinal cord will be
seen, arched over in front of the space by the
occipital bone, behind by the atlas vertebra. In-
sert the point of a pair of bone-forceps or strong
scissors between the cord and the bone, and cut
away the arch of the atlas: do the same with the
arches of the two or three succeeding vertebra,
THE RABBIT. 295
until a small portion of the cord is exposed ; then,
inserting the forceps between the medulla ob-
longata and the occipital bone, remove the roof
of the skull and expose the brain, Great care
will be required to do this without injuring the
brain, especially in the region just internal to
the external auditory opening, where a lobe of
the cerebellum (see § 477) will be found embedded
in a deep pit of the skull wall. Note as you
proceed :
162. The dura mater, a tough fibrous membrane lining
the cranial and spinal cavities: it is continued inwards
between the cerebral hemispheres (§ 480) as the falx
cerebri, and between the cerebrum and cerebellum as -
the tentorium: it is sometimes torn away with the
fragments of bone, sometimes left adhering to the brain:
in the latter case it is advisable to dissect it away from
the dorsal surface of the organ before attempting its
removal.
163. The pia mater,a delicate shining membrane closely
investing the brain and cord, and abundantly supplied with
blood-vessels.
164. Asin the Pigeon (p. 221, § XXV.), the brain com-
pletely fills the skull cavity, the space between the dura
mater and pia mater being reduced to a minimum.
XVI. Cut through the spinal cord about a quarter of
an inch beyond its junction with the brain: care-
fully lever up the brain with the handle of a scalpel,
and cut through all the nerves proceeding from it,
working from behind forwards: dissect away the
olfactory lobes (§ 483) from their attachments.
Remove the whole brain and place it in alcohol,
or, better, in saturated solution of zinc chloride,
296 ZOOTOMY.
for a day or two, and then, after removal of the
pia mater, in strong alcohol (see note, p. 46).
XVII. Place the animal again in the supine position,
and make out in the abdominal cavity, without
cutting or tearing anything:
165. The characters of the liver: its convex anterior
surface applied to the diaphragm, its concave posterior
surface against which the stomach fits, its attached dorsal
and free ventral borders. The dorsal border is attached bya
thin sheet of peritoneum, the coronary ligament, to the
dorsal part of the posterior surface of the diaphragm: a
median vertical sheet of peritoneum, the suspensory
ligament, connects the anterior surface of the liver with
the posterior surface of the diaphragm. This latter ligament
divides the liver into a right and left segment; each
segment is again divided into lobes, of which there are, on
the right side, the ventral right central lobe (Fig. 60,
p- 301, 7c), and the dorsal caudate lobe (cau) closely
applied to the right kidney; and on the left side, the
ventral left central lobe (Zc), the dorsal left lateral
lobe (/./) fitting against the left anterior region of the
stomach, and the small Spigelian lobe (sg), fitting closely
into the lesser curvature (see § 168) of the stomach.
166. The gall bladder, a green pyriform sac, embedded
in the right central lobe of the liver.
167. The cesophagus, or gullet, a narrow tube emerg-
ing from the thorax through an aperture in the diaphragm,
dorsal to the liver, and entering the stomach.
168. The stomach, divided into a large cardiac portion
to the animal’s left, and a smaller pyloric portion to the
right side ; its posterior greater curvature, and anterior
lesser, curvature ; the cardia or entrance of the ceso-
phagus towards the left of the lesser curvature, and the
THE RABBIT. 207
great cardiac dilatation of the stomach to the left of
this point ; the pylorus, or place of exit of the duodenum
(§ 173), at the pyloric end; and the antrum pylori, a
somewhat dilated and thickened portion of the stomach,
immediately to the left of the pylorus.
169. The gastro-hepatic omentum, a sheet of peri-
toneum connecting the posterior surface of the liver with
the lesser curvature of the stomach, and covering the
Spigelian lobe. It is continuous, towards the right side,
with the duodeno-hepatic omentum, which connects
the surface of the liver with the proximal end of the
duodenum (§ 173).
170, The mesogaster, or sheet of peritoneum connecting
the stomach with the dorsal wall of the abdominal cavity.
171. The great omentum, a double fold of peritoneum,
connected with the greater curvature of the stomach, and
usually loaded with fat.
172. The spleen, a long, flat body of a dark red colour,
attached to the cardiac dilatation of the stomach bya sheet
of peritoneum, the gastro-splenic omentum.
173. The duodenum, or portion of the small intestine
immediately succeeding the stomach; it forms a long
U-shaped loop, not bound up with the rest of the small
intestine, but closely connected with a portion of the
rectum.
174. The arrangement of the remainder of the intestine:
the ceecum with the greater part of the colon and part of the
rectum are bound together by a single fold of peritoneum,
the mesentery, which also suspends them to the dorsal
wall of the abdomen: the greater part of the ileum, or
portion of small intestine intervening between the duodenum
and the caecum, is supported by a separate fold of mesentery.
175. The connection of the lower end of the rectum
298 ZOOTOMY.
to the dorsal body-wall by a sheet of peritoneum, the
mesorectum.
176. The passage of the ileum into the proximal end of
the czecum, and the exit of the colon from the same.
177. The termination of the distal or blind extremity of
the cecum in a finger-like, thick-walled process, about three
inches long, the appendix vermiformis.
178. The passage of the rectum posteriorly into the pelvic
cavity, between the bladder and the vertebral column, to
open externally by the anus.
179. The reflections of the peritoneum : its parie-
tal layer, or lining of the abdomen, on reaching the middle
dorsal line is reflected ventralwards, forming the various
subdivisions of the mesentery—mesentery proper, meso-
gaster, mesorectum, &c.—which thus consists of two closely
applied layers, one continuous with the parietal layer of the -
right, the other with that of the left, side: on reaching the
alimentary canal the two layers diverge again and invest it,
forming the visceral layer or peritoneal investment of the
alimentary canal.
XVIII. Turn over the stomach and intestines to the
animal’s right side, and make out :
180. The postcaval vein, or inferior vena cava!
2 A rabbit is hest injected for anatomical purposes with plaster of
Paris (see p. 48, note). Kill the animal with chloroform or potassic
cyanide : as soon as it is dead, open the thorax by cutting through the
sternal ribs of both sides, sufficiently far from the middle line not to
injure the mammary arteries (§ 250), cutting across the posterior end
of the sternum and turning it forwards: slit open the pericardium, and
make a large incision, by a single cut of the scissors, in each ventricle:
all this should be done very rapidly, if possible before the heart has
ceased to beat, as it is desirable to get rid of as much blood as possible:
pass a ligature round the aorta close to its exit from the heart, and give
it a single loose tie: when the bleeding has ceased, sponge the blood
from the heart, and pick out any clots which may have formed in the
left ventricle : pass a cannula through the incision in the left ventricle
into the aorta, tighten the ligature and knot it firmly. By this operation
THE RABBIT. 2909
(Fig. 61, pic), a large vessel, usually gorged with dark blood
after death, passing from the pelvis forwards along the ventral
aspect of the backbone, through a notch in the liver, to the
diaphragm.
181. The aorta (Figs. 60 and 61, d.ao), a smaller vessel
than the postcaval but with thicker walls, of a pinkish
colour, and usually containing comparatively little blood after
death ; it runs partly behind, partly alongside, the postcaval.
182. The coeliac artery (cv.a), given off from the aorta
about an inch posterior to the diaphragm, and supplying the
stomach, liver, spleen, and proximal parts of the duodenum
(see § 198).
183. The anterior mesenteric artery (a.m.a), arising
from the aorta about half or three-quarters of an inch
posterior to the cceliac : it supplies the greater part of both
small and large intestine.
184. The ceeliac ganglion, a soft, pinkish-white mass of irregular
form, situated just anterior to the origin of the anterior mesenteric
artery: it is connected by nerves to the mesenteric ganglion, which
lies immediately posterior to the artery.
185. The splanchnic nerve, emerging from beneath the diaphragm
and passing backwards across the aorta to join the coeliac ganglion : it is
a branch of the sympathetic (§ 239).
186. The gastric branch of the vagus, a small nerve taking a
somewhat spiral course routid the gullet to the stomach : branches from
it join the coeliac ganglion.
187. The left kidney, a brownish-red body of character-
istic shape, just posterior to the anterior mesenteric artery,
the whole of the systemic arteries are injected : the pulmonary arteries
may be filled by proceeding similarly on the right side. The portal
vein is readily injected from its branch to the caudate lobe (Fig.60, caz.),
the cannula being directed towards the main trunk, The injection of
the systemic veins is more difficult: the precavals can be filled from the
external jugular, the postcaval from the external iliac, the cannula, in
both cases, being directed towards the heart.
300 ZOOTOMY.
and connected by the renal artery and vein with the aorta
and inferior cava respectively (see §§ 253 and 254).
188. The left ureter, a delicate white tube, passing from
the inner edge of the kidney backwards and inwards towards
the pelvis: its exact relations will be studied later (§ 262).
189. The left adrenal or suprarenal body, a small,
rounded, yellowish body, placed immediately anterior to the
origin of the renal artery and vein.
tgo. In the female the left uterus, Fallopian tube,
and ovary are now displayed, but are best studied at a later
stage (§§ 288-291).
191. The posterior mesenteric artery (f.m.a), a
small vessel leaving the aorta a short distance posterior to
the left kidney and branching out in the mesorectum to
supply the rectum.
192. The posterior mesenteric vein (Fig. 60, p.m.7’),
a small vessel in the mesorectum formed by the union of
branches parallel with those of the artery of the same name:
it passes directly forwards to join the anterior mesenteric
vein (§ 193).
XIX. Turn the intestines over to the animal’s left side,
and spread out the duodenum, putting its mesen-
tery slightly on the stretch, but taking care not to
rupture it (see Fig. 60). Note:
193. The anterior mesenteric vein (m.v), a large
vessel usually gorged with blood after death, lying in the
duodenal mesentery and receiving veins from the various
coils of the intestine; it is the chief factor of the portal
vein (§ 199).
194. The pancreas (fz), not forming a solid mass, but
consisting of a number of small lobules, looking not unlike
fat, spread all over the duodenal mesentery.
195. The pancreatic duct (fz.d), ashort delicate tube,
The stomach, duodenum, pos-
in outline), with their arteries, veins,
A. The cceliac artery of another specimen (both X §).
Fic. 60.—Lepus cuniculus.
terior portion of rectum, and liver (
and ducts.
302 ZOOTOMY.
The guilet (es) is cut through and the stomach somewhat displaced
backwards to show the ramifications of the coeliac artery (c@.a): the
duodenum (dz) is spread out to the right of the subject to show the
pancreas (fz): the branche: of the bile-duct (¢.4.¢), portal vein (2.2),
and hepatic artery (4.2), are supposed to be traced a short distance into
the various lobes of the liver.
@.m.a, anterior mesenteric artery : caw, caudate lobe of liver, with
its artery, vein, and bile-duct: c.d.¢, common bile-duct : ca.st, cardiac
portion of stomach: ¢.2/.2, common iliac artery: ca.a, coeliac artery :
cy.a, cystic artery : cy.d, cyst'c duct: d.ao, dorsal aorta: wz, proximal,
and du’, distal, linbs of duodenum: dz.a, duodenal artery: dz.4.a
(in A), duodeno-hepatic artery: g.a, ga'tric artery and vein: g.4, gall
bladder : 4.2, hepatic artery: 2.¢/, left bile-duct : /.c, left central lobe of
liver, with its artery, vein, and bile-duct: 2.¢.v, lieno-gastric vein:
4.2, left lateral lobe of liver, with its artery, vein, and bile-duct: ms,
branch of mesenteric artery and vein to duodenum : ms.7, mesorectum :
m.v, chief mesenteric vein : as, cesophazus : ~.72.a, posterior mesenteric
artery: p.m.v, posterior mesenteric vein: gx, pancreas: py.d, pan-
creatic duct: Z.v, portal vein : Ay.s¢, pyloric portion of stomach: re?,
rectum : 7c, right central lobe of liver, with its artery, vein, and bile-
duct : sp, Spigelian lobe of liver, with its artery, vcin, and bile-
duct: sf/, spleen: sf.a, splenic artery,
opening into the ascending or distal limb of the duodenal
loop, an inch or so beyond its junction with the descending
or proximal limb ; the duct will be seen to branch out into
a number of fine tubes which pass to the lobules of the
gland.
196. The right kidney, situated about an inch farther
forward than the left kidney, and having its anterior portion
partly covered by the caudate lobe of the liver; the right
adrenal is in contact with its inner border, immediately
anterior to the right renal artery and vein, and the right
ureter passes from its inner edge backwards to the pelvis.
XX. Turn the intestines into their natural position
again ; tie a double ligature round the gullet close
to the diaphragm and cut it between the ligatures ;
draw the stomach backwards, turn forward the
lobes of the liver, and dissect out the following
structures (see Fig. 60) :
THE RABBIT. 303
197. The common bile-duct (¢.4.¢), a delicate trans-
parent tube containing greenish bile, entering the duodenum
just beyond the pylorus, and receiving hepatic ducts
from the various lobes of the liver and a cystic duct from
the gall bladder.
Calling the varivus hepatic ducts by the same names as the lobes from
which they spring, the arrangement of the whole series of biliary ducts
is as follows :—The cystic duct (cy.d) unites with the right central
duct to form aright bile-duct : the left central and left lateral
ducts similarly unite to form a left bile-duct (4.¢): the mght and
left bile-ducts unite to form the common bile-duct (¢.é.d), which,
about half way between its commencement and its termination in the
duodenum, receives the posterior bile-duct formed by the union of
caudate and Spigelian ducts. They are best demonstrated by
injection from the duodenal aperture.
198. The branches of the coeliac artery (§ 182): shortly after its origin
from the aorta it sends off to the left the splenic artery (sf.a), which
passes to the dorsal side of the cardiac division of the stomach, supply-
ing the latter as well as the spleen: soon after giving off the splenic
artery the coeliac divides into three: of these the middle one, which
continues the direction of the cceliac, is the hepatic artery (/.a) ; it
sends branches to the lesser curvature of the stomach, and then turns
forwards and sends a twig to each lobe of the liver, and a cystic
artery (cy.a) to the gall bladder : coming « ff to the right of the hepatic
is the duodenal artery (dz.a), which supplies the pylorus and the
proximal part of the duodenum : coming off to the left of the hepatic
is the gastric artery (g.a), by which the main part of the stomach is
supplied.
199. The portal vein (/.v), a large, thin-walled vessel,
usually gorged with blood, situated dorsal to (beneath in the
present position of the parts) the artery and duct. Anteriorly
it passes into and breaks up in the liver, sending a branch to
each of the lobes; posteriorly it is constituted by the mesen-
teric vein (§ 193, 7.v) towards the animal's right side, and the
lieno-gastric vein (/.g.v), which brings the blood from the
stomach and spleen towards the left.
200. The ramifications of the branches of the cceliac
304 ZOOTOMY.
and mesenteric arteries, and of the tributaries of the portal
vein in the mesentery and on the walls of the intestine;
in nearly every case an artery and a vein run side by side,
the vein being easily distinguishable from the artery by its
greater diameter and thinner walls, and by retaining its
blood after death.
zor. The lacteals, delicate, transparent, colourless vessels
in the mesentery, running more or less parallel to the
arteries and veins.
XXI. Pass double ligatures round the rectum just
anterior to the pelvic cavity, and round the portal
vein just before it enters the liver (the hepatic artery
and bile-duct may be included in the last liga-
ture). Cut the rectum and vein between the
ligatures, cut through the mesenteric attachments
of the stomach and intestines, and remove them
from the body. Unravel the intestine by cutting
or tearing the mesentery, and make out:
202. The relations of the various divisions of the intestine :
the duodenum passes insensibly into the ileum: the ileum
at its posterior end enters an ovoidal sac with glandular walls,
the sacculus rotundus, which marks the junction between
ileum, colon, and czecum; the caecum preserves a tolerably
uniform diameter for the greater part of its length, finally
narrowing suddenly to form the appendix vermiformis : the
first portion of the colon passes insensibly into the caecum,
of which it appears to form the proximal part ; about one to
two inches from the sacculus rotundus it suddenly narrows
and takes on its characteristic sacculations, at the same
time making a sharp bend so as to run almost parallel to its
former course : the transition between the colon and rectum
is also very gradual, the sacculations of the former becoming
fainter and fainter.
THE RABBIT. 305
203. The'length of the intestine as a whole : it is usually
about 15 or 16 times that of the animal to which it belongs.
The lengths of its five divisions, duodenum, ileum, caecum,
colon, and rectum.
204. The sacculations of the colon occur in three longitudinal rows,
separated by three muscular bands, or teenize coli, which pass, at
equal distances from one another, along the whole length of the colon.
205. The Peyer’s patches, masses of lymphoid tissue occurring in the
form of thickened areas on the walls of the intestine : those on the ileum:
are oval and about half an inch long : on the wide portion of the colon,
close to the sacculus rotundus is a larger patch about three-quarters
of an inch in diameter : the sacculus rotundus itself and the appendix
vermiformis are in reality large Peyer’s patches.
XXII. Cut open the stomach, and parts of the small intestine,
colon, rectum, caecum, and appendix vermiformis : in another
specimen remove the cecum with a small portion of the ileum
and colon, ciear out its contents by directing a stream of water
through it, and either distend with air and dry, or, better,
distend with a 05 per cent solution of chromic acid and place
in a vessel of the same fiuid until hardened : in either case cut
apertures in various parts so as to see the interior. Note the
following points in the internal structure of the alimentary
canal :
206. The three coats of the stomach: the outer peritoneal invest-
ment, the middle muscular layer, and the inner layer of mucous
membrane: the great thickness of the muscular layer in the antrum
pylori: the slightly different character of the mucous membrane in the
cardiac and pyloric regions : the irregularly longitudinal rugee into which
the mucous membrine is raised.
207. The thick projecting rim, or pyloric valve between the stomach
and duodenum,
208, The prominent aperture of the bile-duct in the duodenum
just beyond the pylorus.
209. The three coats of the intestines : much thinner, for the most
part, than those of the stomach.
210, The irregular transverse ridges or valvule conniventes of the
mucous membrane of the small intestine : the minute conical projections
or villi which beset these: the latter can only be seen to advantage by
examining under water.
x
306 ZOOTOMY.
211, The rounded aperture between the sacculus rotundus and the
colon, its margins forming the ileo-colic valve,
212, The spiral valve of the caecum, a narrow spiral band projecting
into the cavity of the blind gut and corresponding with the external
marking.
213. The intra-colic valve, a prominent fold occurring at the bend
between the two portions of the colon.
214. The thick glandular walls of the appendix vermiformis and
sacculus rotundus: the very thin walls of the caecum itself, and the
minute papillary elevations with which its inner surface and that of the
spiral valve are beset.
215. The absence of villi in the large intestine : the papillary surface
of the mucous membrane cf the colon, the smooth character of that of
the rectum.
XNIII. Tie the postcaval vein at the points where it
enters and leaves the liver: remove the whole of
the liver, with the exception of the part which
surrounds the postcaval. Note:
216. The transparent, shining central tendon of the
diaphragm, and the muscular fibres which radiate from
it to the body walls, and are collected dorsally into
two strong bands of muscle, the pillars of the dia-
phragm, which pass backwards to their origin from the
anterior lumbar vertebre.
217. The aorta, passing from the abdominal cavity for-
wards between the pillars of the diaphragm.
218. The ceesophagus, passing through an aperture in the
dorsal region of the central tendon.
219. The postcaval, passing through an aperture
situated to the right and ventral of that for the gullet.
220. The three hepatic veins (Fig. 61, 4.v), by which
the blood is taken from the liver to the postcaval : they are
best seen by slitting up the intra-hepatic part of that vein:
two of them enter the postcaval immediately posterior to
THE RABBIT. 307
the diaphragm, the third near the point at which the
postcaval enters the liver.
221, The posterior phrenic veins (2.4) taking the blood from the
abdominal surface of the diaphragm to the postcaval.
XXIV. Cut away enough of the ribs on one or both
sides to get a good view of the interior of the
thorax, and make out:
222. The relations of the pleurz: the outer or parietal
layer of each lines its own half of the thorax, to the walls of
which it adheres closely (§ 161): the adjacent or inner faces
of the two parietal layers form a double median vertical
partition, the mediastinum: the mediastinal space
included between the two layers of this partition is largely
occupied by the heart and its surrounding pericardium, and is
thus practically obliterated in the greater part of its extent: it
is, however, readily made out in the interval between the heart
and the sternum, where it is called the ventral (anterior)
mediastinal space : at the entrance of the bronchi each
pleura is reflected over the corresponding lung, forming the
thin, closely adherent visceral layer.
XXV. Cut through the posterior end of the sternum:
separate the mediastinum from the dorsal surface
of the bone and turn it forwards: open the
pericardium by a longitudinal incision, and make
out:
223. The relations of the pericardium: its outer or
parietal layer forms a loose bag investing the heart, and,
at the origins of the great vessels (§§ 229-232 and 237),
reflected on to the surface of the heart, forming the thin,
closely adherent visceral layer: in the space included
between the two layers is contained a small quantity of
colourless pericardial fluid.
xX 2
308 ZOOTOM\.
XXVI. Dissect away the pericardium, the thyntus gland,
and any fat about the base of the heart which may
obscure the vessels coming from it. Follow out
these vessels to the head and anterior extremities
by clearing away the muscle, connective tissue,
fat, &c., by which they are surrounded. Also
clean the aorta ($ 237) and postcaval, and follow
out their branches into the posterior extremities,
taking care not to injure the ureters ($ 262),
and the vasa deferentia (§ 267) or uteri ($ 288).
Make out:
224. The left ventricle (Fig. 61, 77), which forms the
whole apex of the heart: it is lighter in colour than the
rest of the organ and harder to the touch.
225. The right ventricle (77), divided by an oblique
depression from the left ventricle: it is darker in colour
than the left and softer to the touch.
226. The right and left auricies (av, /.au), situated
above (anterior to) the corresponding ventricles : they are
small, dark, thin-walled chambers, slightly overlapping the
bases of the ventricles.
227. The ramifications of the coronary artery and
vein over the surface of the ventricles.
228. The bifurcation of the trachea, at about the level of
the base of the heart, to form the two bronchi, one of
which passes to each lung.
229, The pulmonary artery (#.7), proceeding from the
conelike anterior prolongation of the right ventricle, and
passing forwards and to the left : it soon divides into a right
and a left trunk, one of which passes to each lung.
230 The pulmonary veins (.v), returning the blood
from the lung to the left auricle. They are best seen at a
later stage (see § 306).
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Fic. 61.—Lepus cuniculus, The vascular system (X 4)-
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310 ZOOTOMY.
The apex of the heart is somewhat displaced towards the left of the
subject : the arteries of the right and the veins of the left side are in
great measure removed. ;
a.ao, arch of the aorta: @.efg, internal mammary artery : ¢.f, anterior
facial vein: a.m, anterior mesenteric artery: a.ph, anterior phrenic
vein: az.v, azygos vein: 67, brachial artery: ¢.2/.a, common iliac
artery: ¢.7/.2, common iliac vein: ca, coeliac artery: dao, dorsal
aorta: ¢.¢, external carotid artery: ¢.2/.2, external iliac artery : ¢.2/.z,
external iliac vein: ¢.7z, external jugular vein : /m.a, femoral artery :
fm.v, femoral vein: 2.v, hepatic veins: z.c, internal carotid artery : ics,
intercostal vessels: 7.7/.z, internal iliac artery: z.2/.v, internal iliac
vein : ¢.jz, internal jugular vein: 7./, ilio-lumbar artery and vein : zy,
innominate artery: /.az, left auricle: /.7.¢, left common carotid artery :
Lpre, left precaval vein: /.7, left ventricle : #.sc, median sacral artery :
p.a, pulmonary artery: p.epg, epigastric artery and vein : 2.f, posterior
facial vein: f#.#z, posterior mesenteric artery: 4.£4, posterior phrenic
veins : gfc, postcaval vein: g.v, pulmonary vein: 7, renal artery and
vein: v.au, right auricle: 7.c.c, right common carotid artery: r.pre,
right precaval vein: xv, right ventricle: sc/.a, subclaviau artery : scl.v,
subclavian vein : sf, spermatic artery and vein: s.7s, superior vesical
artery and vein : zé, uterine artery and vein: v7, vertebral artery.
231. The two precaval veins, or venz cave supe-
riores (prc, /.prc), passing from the anterior end of the
thorax towards the base of the heart: each is formed by
the union of the subclavian vein (sc.v), from the
corresponding arm, and the external jugular vein
(e.ju) already noticed (§ 127) from the head ; the right pre-
cavalis seen at once to enter the night auricle: the left
trunk is seen, on lifting up the heart, to curve round the
dorsal side of the base of that organ, and enter the same
chamber. Sometimes the two external jugular veins unite
with one another by a transverse connecting trunk in the
posterior region of the neck.
The external jugular is constituted anteriorly by the anterior facial
vein (a.f), which runs just within the ramus of the mandible, and the
posterior facial vein, (4./), coming from the external ear ; near its junc-
tion with the subclavian, it receives the internal jugular vein (7.72),
which runs close alongside the trachea, and receives the blood from the
brain,
THE RABBIT. 311
232. The thoracic portion of the postcaval vein (f7c),
passing forwards from the diaphragm to the right auricle.
233. The anterior phrenic vein (c.f), passing forwards from the
diaphragm, alongside the postcaval, and pouring its contents into the
right precaval.
234. The cesophagus, or gullet, passing from the
anterior boundary of the thorax, dorsal to the trachea and
between the lungs, backwards to its aperture in the
diaphragm.
235. The paired phrenic nerves, passing from the
anterior boundary of the thorax backwards to the diaphragm,
which they supply: the right nerve runs alongside the right
precaval, across the right auricle and along the postcaval,
the left nerve runs along the left precaval and then passes
just internal to the left lung:
Traced forwards, the phrenic is found to take its origin from the sixth
cervical nerve: if followed beyond the thorax, it should be left until the
nerves of the neck (§§ 244-246) are dissected.
236. The thoracic portions of the vagi (see § 186 and 244) : the right
vagus enters the thorax to the right of the trachea along which it runs,
thence passing on to the gullet and so through the diaphragm to the
stomach: the left nerve runs at first parallel to the left precaval,
finally also reaching the gullet, along which both nerves take a spiral
course.
237. The aorta (ao), a large, elastic, thick-walled vessel,
of a whitish colour, proceeding from the base of the heart
behind the pulmonary artery ; it rises clear of the heart, then
bends over to the left side, forming the arch of the
aorta (a.av), and passes backwards, arching over the left
bronchus (§ 228) to reach the ventral face of the spinal
column, along which it passes as the dorsal aorta (d.ao)
throughout the whole length of the thorax and abdomen,
dividing at Jast into the two common iliac arteries
312 ZOOTOMY.
(cla, § 258) which pass backwards and outwards to the
hind legs. The aorta is united to the pulmonary artery
by a short ligament, the remains of the embryonic ductus
arteriosus.
238. The thoracic duct, or main trunk of the lymphatic system: a
slender, thin-walled tube, lying to the dorsal side of the aorta, and
pouring its contents into the left subclavian vein at its junction with
the left external jugular: it is best seen by pulling the thoracic aorta
somewhat to the right.
239. The thoracic portion of the sympathetic nerves,
slender white cords, lying one on each side of the aorta,
and having at intervals ganglia, which lie on the heads of
the ribs; each is continued backwards into the abdomen
(§ 185) and forwards into the head (§ 245).
240. The azygos or (right) cardinal vein (az.v), best
seen by turning the heart and lungs over to the left side: it
lies immediately to the right of the thoracic aorta, receiving
the intercostal veins (zs) from the spaces between the
seven posterior ribs: anteriorly it pours its contents into
the right precaval. The blood from the five anterior inter-
costal spaces is returned, on each side, into an anterior
intercostal vein which enters the corresponding pre-
caval.
241. The innominate artery (2), springing from the
arch of the aorta towards its right side; it gives off at its
origin the left common carotid artery (/.cc) and then,
passing forward, divides into the right common carotid
(v.cc) and right subclavian (s.c/.a).
242. The left subclavian artery, taking its origin
from the left side of the arch of the aorta.
243. The course of the common carotid arteries:
each passes up the side of the neck, external to the trachea
and internal to the external jugular, gives off branches to
THE RABBIT. 313
the larynx, and, at about the level of the anterior end of
the larynx, divides into the internal carotid (¢.c), which
passes dorsalwards to reach the brain, and the external
carotid (¢.c), which supplies the greater part of the head :
the internal carotid may be recognised as being the first
important branch given off from the outer side of the
common carotid: the external carotid divides almost
immediately into, branches for the jaws, eye, &c.
244. The cervical portion of the vagus, a nerve running
to the outer side of each common carotid.
Traced backwards, the right vagus is seen to pass across (ventral to)
the rizht subclavian artery, the left across the arch of the aorta, to
enter the thorax, where they have already been seen (§ 236).
245. The cervical portion of the sympathetic, seen by lifting up
the carotid and carefully separating it from the vagus: it isa flat pale
nerve lying immediately dorsal to the artery: traced backwards, it
enlarges at about the level of the first rib into the posterior cervical
ganglion, and thus enters the thorax, where it has already been seen.
246. Traced forwards, the sympathetic is seen to enlarge, at a level
just anterior to the larynx, into the anterior cervical ganglion, im-
mediately external to which is a similar enlargement of the vagus, the
ganglion of the root: crossing both nerves and the carotid artery at
about the same level, but obliquely from behind forwards and inwards,
is the slender tendon of the digastric muscle, and iamediately
behind and parallel to this the hypoglossal nerve.
247. The thyroid gland, a brownish mass, consisting
of two lobes applied to the sides of the larynx, and con-
nected across the ventral face of the latter by a band-like
intermediate portion.
248. The large thyroid cartilage, forming the anterior
part of the larynx, and the ring-like cricoid cartilage,
forming its posterior part.
249. The submaxillary gland has been already seen: its duct
(Wharton’s duct) is a very fine tube proceeding from its inner face to
open on the floor of the mouth,
314 ZOOTOMY.
250. The course of the subclavian arteries: each,
soon after its origin, divides into the vertebral artery (vr),
which dives inwards, and then passes forwards through the
vertebrarterial canal of the cervical vertebrae (§ 24), to
supply the brain and spinal cord ; and the brachial artery
(4r), which passes directly outwards, and sends branches
to the forelimb and shoulder-girdle, giving off also the
internal mammary artery (a.efg), a small vessel which
runs backwards over the inner face of the wall of the
thorax just external to the’sternum.
251. The thoracic arteries, small vessels given off in pairs from
the thoracic aorta, and supplying the seven posterior intercostal spaces.
The five anterior intercostal spaces are supplied by a branch of the
internal mammary.
252. The phrenic arteries, arising from the aorta and supplying
the diaphragm.
253. The renal arteries (7), of which the right comes
off almost immediately posterior to the anterior mesenteric
(§ 183), and the left about half an inch posterior to the
right; each passes immediately to the hilus (§ 261) of the
corresponding kidney.
254. The renal veins (7), each of which runs parallel
and just posterior to the corresponding renal artery,
receives a large vein from the dorsal wall of the abdomen,
and pours its contents into the postcaval.
255. The lumbar arteries and veins, small vessels supplying the
dorsal walls of the abdomen, and springing from the aorta and_post-
caval respectively.
256. The spermatic arteries and veins (sm), taking
their origin somewhat posteriorly to the posterior mesenteric
artery, from the aorta and postcaval respectively, and passing
to the testes (§§ 266 and 268), or ovaries (§ 291).
257. The median sacral artery (m.sc), a small trunk arising from
THE RABBIT. 318
the dorsal side of the aorta, and passing backwards to the pelvis: it
corresponds to the caudal continuation of the aorta (see pp. 67, 115,
235).
258. The common iliac arteries (¢.22.a), formed by
the bifurcation of the aorta: each gives off soon after its
origin the ilio-lumbar artery (z./) to the posterior part
of the dorsal abdominal walls, and then almost immediately
divides into the internal iliac (¢.2/.2), which passes along
the dorsal wall of the pelvic cavity, and the external iliac
(e.2.a), which gives off an artery to the bladder and uterus,
and then, passing beneath Poupart’s ligament, becomes the
femoral artery (/m.a), and supplies the leg. Immediately
external to Poupart’s ligament the femoral gives off the
posterior epigastric artery (2.efg), which is distributed
to the ventral abdominal walls.
259. The ilio-lumbar veins (7./), large vessels which
enter the postcaval just anterior to the bifurcation of the
aorta.
In some cases the left ilio-lumbar instead of directly entering the
postcaval, turns forwards, runs parallel to the latter, receives the left
spermatic, and enters the postcaval a little posterior to the entrance ol
the left renal.
260. The trifurcation of the inferior cava at its posterior
end into the two outwardly directed external iliac veins
(e.2/.7), and the median, backwardly directed common iliac
vein (c.z/.v), The external iliacs, like the corresponding
arteries to which they are parallel, are the intra-abdominal
portions of the femoral veins ( /m.v), by which the blood
is returned from the legs; they also receive the blood from
the bladder and uterus: the posterior epigastric veins
(f. epg), open into the femorals immediately external to
Poupart’s ligament. The common iliac is formed by the
union of the two internal iliac veins (¢.2/.v), which run
316 ZOOTOMY.
parallel and internal'to the corresponding arteries along
the dorsal wall of the pelvis.
XXVII. Carefully dissect away the peritoneum from the
kidneys, ureters, and genital organs, already noticed,
as well as the fat which usually obscures them.
Make out :
261. The kidneys, compact red bodies of characteristic
shape, lying one on either side of the lumbar region, the
right considerably in front of the left. Each has on its
inner edge a depression or hilus, and is covered by
peritoneum on its ventral side only.
262. The ureter (Fig. 62, A and B wr) a long white tube
springing from the hilus, about one-eighth of an inch in
diameter in its upper part, but rapidly getting narrower :
the two ureters pass somewhat inwards towards the middle
hne, and then backwards almost parallel with one another,
and enter
263. The bladder (4/), a pyriform sac, which may vary
greatly in size and appearance, according to its state of
distension ; when full, it projects some distance into the
abdominal cavity, and its walls appear very thin and show
the bright yellow urine through them ; when empty it hardly
appears above the pubes, and its walls appear thick and
opaque : it may be inflated trom the urethra (§ 153). The
ureters enter it about half way (in the collapsed condition)
between its broad anterior end, or fundus, and its narrow
neck.
264. The adrenals, or suprarenal bodies, small,
yellowish-white bodies, of which the right is close to the
corresponding kidney, while the left lies in the anterior angle
between the aorta and renal artery.
Ln the Male.
265. The penis (A, cc, ¢s, ¢.f), projecting backwards
THE RABBIT. 317
from the posterior edge of the symphysis pubis, and enclosed
in a loose fold of skin, the prepuce: it is strengthened
Fic. 62.—Lepus cuniculus, The urinogenital organs, A, of
the male, B, of the female, from the left side (4 nat. size).
The kidneys and proximal ends of the ureters, and in B the ovaries,
Fallopian tubes, and uteri, are not shown.
an, anus: 6/, urinary bladder: ¢.c, corpus cavernosum: ¢.s, corpus
spongiosum: ¢.g7, Cowper’s gland: g.c/, glans clitcridis: ¢.f, glans
penis: Z.g/, perineal gland: /.gt’, aperture of its duct on the perineal
space: pr, anterior, 7’, posterior, and pr”, lateral, lobes of prostate :
ret, rectum: ~.gl, rectal gland: w.g.a, urinogenital aperture: um,
uterus masculinus: wz, ureter: va, vagina: v4, vestibule: vd, vas
deferens.
ventrally by the two hard, closely applied corpora
cavernosa (cc), which, at the proximal end of the organ,
318 ZOOTOMY.
diverge, forming the crura penis, and are attached to the
ischia : dorsally it is soft and yielding, consisting only of
the thin vascular corpus spongiosum (cs, see § 279): its
free end is formed by a soft conical body, the glans penis
(g.p), which projects beyond the prepuce, and bears the slit-
like aperture (w.g.a) of the urethra, a canal traversing the
penis.
266. The scrotal sacs, situated one on each side of
the penis, and having their cavities in communication, by a
widish aperture, with the peritoneal cavity, so that by pulling
upon the spermatic artery and vein (§ 256) the testis
which each contains can be retracted into the abdomen.
267. The vasa deferentia (v.c), two whitish tubes
resembling the ureters in appearance and size: they pro-
ceed from the scrotal sacs into the peritoneal cavity, and
then each curves over the corresponding ureter to reach the
dorsal side of the bladder.
XXVIII. Slit open one of the scrotal sacs along its
ventral wall, and make out:
268, The testis, a pinkish-white, ovoidal body, about an
inch long in a full-grown rabbit
269. The epididymis, an irregular, convoluted body,
forming the greatly coiled proximal end of the vas deferens :
it consists of the caput epididymis, applied to the
anterior end of the testis, and connected by a narrow
band running along the inner edge of the latter, with
the cauda epididymis, which is continued posteriorly
beyond the testis, and, anteriorly, gives origin to the vas
deferens. The caput is usually much obscured by a mass
of fat, in which run the spermatic artery and vein.
270. The gubernaculum, a short cord connecting the posterior end
of the cauda epididymis with the interior of the scrotal sac.
THE RABBIT. 319
271. The coats of the scrotal sac: these are, a layer of skin exter-
nally; then a layer of loose connective tissue, the dartos; then a
layer of muscle, the cremaster, continuous with the internal oblique
muscle of the abdomen ; and, lastly, an internal lining of peritoneum,
the tunica vaginalis.
272. The mesorchium, a double fold of peritoneum
suspending the testis and vas deferens to the dorsal wall
of the scrotal sac, after the manner of a mesentery; its two
layers are continuous with the peritoneal lining of the sac
(tunica vaginalis), and are reflected over the testis.
XXIX. Dissect away the kidneys, ureters, and scrotal
sacs from the surrounding parts: cut away the
symphysis. pubis with bone forceps: cut through
the two corpora cavernosa (§ 265) by which the
penis is attached to the ischia. Remove the
whole of the urinogenital organs from the body,
together with the posterior end of the rectum,
and pin them out in a dissecting dish, with the
dorsal surface uppermost, taking care to preserve
the natural relation of the parts. Carefully dis-
sect away all fat and connective tissue, gradually
separate the rectum from the other organs and
turn it aside, making out :
273. The uterus masculinus (zm), a large sac,
slightly bilobed at its anterior end, and lying against the
dorsal side of the neck of the bladder. The vasa deferentia,
after curving round the ureters, are seen to pass between
this sac and the bladder.
274, The prostate (7), a glandular mass, in relation with
the neck of the bladder and the uterus masculinus.
It consists of five lobes: an anterior (gr), so closely applied to the
dorsal wall of the uterus masculinus as to be almost inseparable from
it: another posterior (#r’), more prominent than the first, bilobed
anteriorly, and easily separable from the uterus masculinus; and two
320 ZOOTOMY.
small lateral lobes (f7”), lying along the sides of the neck of the
bladder.
275. Cowper’s glands (c.g/), a pair of brown, ovoid masses, imme-
diately behind the posterior lobe of the prostate, and enclosed in a
layer of mu-cle.
276. The rectal glands (7.97), two brown elongated
glands, about an inch long and a quarter of an inch wide,
situated one on either side of the rectum.
277. The perineal glands (/.g/), similar in appear-
ance to the rectal glands, but not more than half an inch
long: they lie, one on either side of the extremity of the
penis, and are in relation externally one with each of the
hairless perineal spaces, on the surface of which its duct
opens on a small papilla (/.g/’).
278. By slitting open the uterus masculinus along its
dorsal wall, the vasa deferentia are seen to open into its
ventral wall, near its junction with the bladder.
279. The corpus spongiosum (c.s), a quantity of
extremely vascular tissue surrounding the urethra, from
about the posterior boundary of Cowper’s glands to the
glans penis, with which it becomes continuous: to see it
satisfactorily, the rectum and rectal glands should be
entirely removed.
XXX. Turn the organs with the ventral side upper-
most, and make a median incision along the
whole length of the penis, beginning at the
glans and cutting through the fibrous septum
between the corpora cavernosa: continue the
incision forward so as to open the bladder along
its ventral wall. Note:
280. The small apertures of the ureters in the dorsal
wall of the bladder at about the junction of its middle and
posterior thirds.
THE RABBIT. 321
281. The verumontanum or colliculus seminalis,
a small rounded elevation on the dorsal wall of the urethra,
just posterior to its junction with the bladder.
282. The opening of the uterus masculinus into the
urethra: a crescentic aperture just in front of the anterior
edge of the verumontanum.
283. The openings of the prostatic ducts, minute apertures,
usually about four in number, on each side of the verumontanum.
284. The openings of the ducts of Cowper’s glands, four
extremely minute apertures in the dorsal wall of the urethra, about
half an inch posterior to the verumontanum.
In the Female.
285. The vulva, or external urinogenital aperture,
(Fig. 62, B, w.g.@) guarded by two tolerably prominent folds
of mucous membrane, the labia majora, and leading into
a wide tube, the vestibule, situated immediately ventral to
the extremity of the rectum.
286. The clitoris (ac, g.c/), a hard, rod-like body em-
bedded in the ventral wall of the vestibule: it consists of
two closely applied corpora cavernosa (c.c), resembling
the bodies of the same name in the male (§ 265), and, like
them, diverging anteriorly as the crura clitoridis to be
attached to the ischia: the free end of the clitoris is
formed by the glans clitoridis (g.¢7), a small soft conical
body between the anterior (ventral) ends of the labia
majora.
287. The vagina (Figs. 62, B, and 63, va), a widish tube
lying between the bladder and the rectum; like the other
reproductive organs, it varies greatly in size according to the
age of the animal.
288. The uteri (Fig. 63, nz, ut), paired tubes proceed-
ing from the anterior end of the vagina, and proceeding
outwards towards the flanks; they are comparatively wide
Y
abe ZOOTOMY.
at their posterior or vaginal ends, but become narrow
anteriorly and pass almost insensibly into
289. The Faliopian tubes (7.4), or anterior extremities
of the genital ducts: they are somewhat convoluted tubes
of small calibre, ending anteriorly in a wide, membranous,
funnel-shaped extremity with fimbriated margin.
fle 7
Fic. 63.—Lepus cuniculus. The anterior end of the vagina, with
the right uterus, Fallopian tube, and ovary (nat. size).
Part of the ventral wall of the vagina is removed, and the proximal
end of the left uterus is shown in longitudinal section.
fit, Fallopian tube: 72./, its peritoneal aperture: Zz, left uterus:
Z.ut’, left os uteri: v.z¢, right uterus: 7.2’, right os weri: s, vaginal
septum: va, vagina.
290. The broad ligament, a sheet of peritoneum, sus-
pending the uterus and Fallopian tube to the dorsal body
wall.
291. The ovaries (ov), ovoidal bodies, about half an
inch long and a quarter wide, situated just external to the
fimbriated extremity of the Fallopian tube: they have a
whitish colour, and are studded over with small round
THE RABBIT. 323
pinkish projections, the Graafian follicles, each of which
contains an ovum.
XXXI. Cut through the symphysis pubis, and dissect
away the urinogenital organs from the body, fasten
them with the dorsal side upwards, and make out
the rectal and perineal glands, which have the
same relation as in the male (see §§ 276 and 277);
then remove these glands along with the rectum,
and make out
292. The vestibule (Fig. 62, B, 24), a wide tube, with.
the dorsal wall of which the rectum was in contact: with
its anterior end the bladder and vagina are connected,
while, posteriorly, it opens externally by the vulva. It
has precisely the relations of the urethra of the male (§ 265),
and its walls are invested with a vascular tissue answering
to the corpus spongiosum (§ 279).
293. Cowper’s glands (c.g/), a pair of small whitish masses, lying
on the dorsal wall of the vestibule at about the middle of its length.
XXXII. Turn the organs with their ventral side
upwards, make a median longitudinal incision
through the vestibule, and continue it forwards
until the cavity of the bladder is exposed: make
a median longitudinal incision through the ventral
wall of the vagina: afterwards slit up one of the
uteri and the corresponding Fallopian tube along
their whole length. Make out :
294. The small aperture of the ureters in the dorsal wall
of the bladder about half way between its fundus and
its neck.
295. The almost insensible passage from the bladder to
the vestibule, the neck of the former being very wide.
296. The irregular ruge or ridges of mucous membrane
into which the walls of the vestibule are raised.
Y 2
324 ZOOTOMY.
297. The large, somewhat crescentic aperture by which
the vagina opens into the vestibule.
298. The small apertures of the ducts of Cowper’s glands, on the
dorsal wall of the vestibule.
299. The os uteri (Fig. 63, 7.2’), a small aperture with
a greatly thickened and rugose margin, on each side of the
anterior end of the vagina, and leading into the corre-
sponding uterus. Between the two ora uterorum is a rudi-
mentary vertical septum (s) tending to divide the vagina into
two tubes.
300. ‘The very thick walls of the uterus, consisting of an
outer muscular Jayer and an inner mucous layer raised up
into Rig large and prominent ruge.
1. The smooth walls of the Fallopian tube and the
eee of that tube posteriorly into the uterus, and
anteriorly by its funnel-like fimbriated extremity (77)
into the peritoneal cavity in the immediate neighbourhood
of the ovary.
In both sexes.
XXXIII. Make a section of one of the kidneys, through
the hilus, and parallel to the dorsal and ventral
faces of the organ. Note:
302. The sinus, a large cavity excavated in the substance
of the kidney into which the hilus leads.
303. The pelvis, a large funnel-like dilatation of the
proximal end of the ureter, nearly filling the sinus: it ends
in a number of small subdivisions, the calices.
304. The urinary pyramid, a conical mass of kidney
substance, projecting into the pelvis.
305. The distinction between the superficial or cortical
portion of the kidney which has a dotted appearance,
and its central or medullary portion, marked with strie
which radiate outwards from the pyramid.
THE RABBIT. 325
XXXIV. Carefully remove from the body the heart
and lungs, together with the posterior end of the
trachea and recognisable portions of the aorta
and ven cave. Fasten out the organs under
water, with their dorsal surface uppermost, and
make out:
306. The course of the pulmonary arteries and
veins: the arteries remain single until they reach the
lungs; the veins are two from each lung, and enter the
left auricle separately, in the U-shaped space between the
two precavals.
XXXV. Cut through the pulmonary arteries and veins
close to the lungs, and separate the latter from the
heart : make out :
307. The division of the left lung into two lobes, an
anterior and a posterior: the former is deeply divided
by a transverse fissure.
308. The division of the right lung into four lobes, called,
passing from before backwards, the anterior accessory,
the anterior, the posterior, and the posterior acces-
sory: the “accessory” lobes are considerably smaller than
the other two: the posterior accessory is situated internal to
the root of the lung and rather to the left side of the thoracic
cavity.
309. The cartilages of the trachea and bronchi,
incomplete rings surrounding the ventral and lateral aspects
of the tubes, but leaving their dorsal sides unstrengthened.
310. The division of the left bronchus into two tubes, one for each
lobe.
311. The subdivisions of the right bronchus: it first gives off a
branch on the outer side to the anterior accessory lobe, then one on the
ventral side to the anterior lobe, and finally divides into two branches for
the posterior and posterior accessory lobes, In some instances the
326 ZOOTOMY.
bronchus for the anterior accessory lobe is given off from the trachea
immediately before its bifurcation.
312. By scraping away the lung substance the bronchi may be further
followed : their cartilages soon lose the incomplete annular form, and
become irregular isolated patches: the branches given off from the
bronchi into the substance of the lung come off at an acute angle.
XXXVI. In the heart cut away the outer walls of both
auricles, so as to expose their cavities, taking
care not to injure the venae cave or pulmonary
veins. Note:
313. The division of each auricle into a larger, smooth-
walled, posterior portion or atrium, and a small, anterior
portion or appendix auriculz, which projects over the
base of the ventricle, and the walls of which are strength-
ened internally by a network of muscular bands, the
musculi pectinati.
314. The septum auricularum, or muscular division
wall between the auricles.
315. The fossa ovalis, an oval area on the septum
rather thinner than the rest of it; it is seen best from the
left side by holding the septum up to the light, and is sur-
rounded by a slightly raised margin, the annulus ovalis.
It marks the position of the foramen ovale of the foetus.
316. The auriculo-ventricular apertures, by which
the auricles respectively communicate with the ventricles.
317. The apertures of the pre- and postcaval
veins into right auricle: that of the right precaval is in the
anterior (upper) end of the auricle ; that of the postcaval
in the postero-dorsal region, a membranous fold, the
remains of the foetal Eustachian valve, extending from
its posterior margin towards the septum; that of the
left precaval is immediately to the left of, and posterior
to, the Eustachian valve, and is bounded behind (below in
THE RABBIT. 327
the upright position of the heart) by a semi-lunar fold, the
valve of Thebesius.
318. The aperture of the coronary vein, by which
the blood is brought back from the substance of the heart ;
it isa small round opening just within the margin of the
tunnel-like aperture of the left precaval.
319. The apertures of the pulmonary veins into
the left auricle. .
XXXVII. Cut away both auricles so as to expose the
bases of the ventricles: cut away all but about
an eighth of an inch of the aorta and pulmonary
artery : pour water into the ventricles through the
auriculo-ventricular apertures. Note:
320. The auriculo-ventricular valves, two sets of
membranous flaps, which, when the filled ventricles are
squeezed, come together at their edges and close the
auriculo-ventricular apertures; but when the pressure is
released fall down into the ventricles. On the left side are
two flaps, together constituting the mitral or bicuspid
valve; on the right side are three flaps, together con-
stituting the tricuspid valve.
321. The semilunar valves, of which there are three
at the origin of both the pulmonary artery and aorta:
all three valves, in each case, are in one plane, and
when there is fluid in the artery, come together by
their edges, and close the passage to the ventricle; but
when the ventricle is squeezed, the pressure forces them
aside, and causes them to flap back against the walls of
the artery.
322. The sinuses of Valsalva, slight dilatations of
the aorta and pulmonary artery, just anterior to (above)
the semilunar valves.
323. The apertures of the coronary arteries, by which
328 ZOOTOMY.
the heart is supplied with blood, situated in two of the aortic
sinuses of Valsalva.
XXXVIII. Remove the outer walls of both ventricles,
by making first a transverse incision along the
base of each, and then taking from its extremities
converging incisions nearly to the apex of the
heart. Make out:
324. The comparatively thin walls of the right ventricle,
and the extremely thick walls of the left ventricle.
325. The septum ventriculorum, or partition between
the ventricles; it is convex towards the right, concave
towards the left side, so that, in transverse section, the
cavity of the right ventricle appears semilunar, that of
the left almost circular.
326. The columne carnee, muscular ridges into which
the inner surface of the ventricular walls is raised. One
of those in the right ventricle usually takes on the form
of a cord extending across the cavity from the inner to the
outer side, and called the moderator band.
327. In the right ventricle, the three flaps of the
tricuspid valve attached by their anterior edges round
the auriculo-ventricular aperture: their irregular posterior
edges, which depend into the ventricle, are attached by
strings, the chordz tendinez, to small conical elevations
of the ventricular wall, the musculi papillares.
328. In the left ventricle, the two flaps of the mitral
valve, attached in the same manner as those of the tricuspid.
The papillary muscles are, however, fewer in number and
considerably larger in size.
329. The conus arteriosus, or infundibulum, a pro-
longation of the left anterior angle of the right ventricle, in
the apex of which is the aperture of the pulmonary artery.
330. The aperture of the aorta in the left ventricle,
THE RABBIT, 329
situated within and dorsal to the auriculo-ventricular
aperture.
XXXIX. Dissect away the skin from the side of the
head, and make out:
331. The masseter, a large mass of muscle covering
the posterior half of the mandible.
It arises from the lower edge of the jugal arch, and is inserted into
the lower border of the mandibular ramus.
332. The muscular branches of the seventh or facial
nerve, passing from behind forwards over the outer surface
of the masseter.
Traced backwards, these nerves are seen to spring from a single trunk
which makes its exit through the stylo-mastoid foramen (§ 55).
333. The parotid (salivary) gland, a soft, irregular,
pinkish mass, situated just in front of and below the
external ear.
Its fine duct (Stenson’s duct) passes forwards from its anterior
edge, along with the branches of the seventh nerve, and in front
of the masseter muscle dips inwards, to open into fhe interior of the
mouth.
334. The infraorbital (salivary) gland, a large lobu-
lated mass lying in the antero-inferior region of the orbit,
partly outwards and partly within the cavity.
Its duct passes downwards from its inferior edge, to open into the
cavity of the mouth.
XL.1 Cut away, with bone-forceps, the supraorbital
process of the frontal (§ 47), working from behind
forwards, and making out:
335. The superior oblique muscle of the eye, arising
1 The following sections (§§ 335—353) cannot conveniently be
worked out in a specimen from which the brain has been removed,
unless that operation has been conducted with very great care.
330 ZOOTOMY.
from the postero-internal region of the orbit along with the
recti ($ 338) and passing forwards and upwards to the under
surface of the anterior end of the supraorbital process : there
it passes through a tendinous loop attached to the bone,
and then passing downwards and slightiy backwards is
inserted into the eyeball.
336. The lacrymal gland, a pinkish mass situated in
the upper and posterior region of the eyeball.
337. The Harderian gland, a white, opaque, lobulated
body situated in the anterior region of the eyeball.
338. The four recti and the inferior oblique have the same
relations as in the lower Vertebrata ( p. 77, §§ 192—194, and p. 78, §§
201, 202).
339. The third, fourth, and sixth cerebral nerves, issuing from the
sphenoidal fissure, and having the same general distribution to the eye-
muscles as in the lower Vertebrata (pp. 77, 78, §§ 195—197, 203).
340. The retractor bulbi, a conical muscle lying immediately within
the recti, and forming a sheath round the optic nerve: it is supplied by
the sixth nerve.
341. The orbito-nasal nerve, or first division of the fifth, leaving the
skull through the sphenoidal fissure and passing along the upper edge of
the inner wall of the orbit.
342. The optic nerve, leaving the skull by the optic foramen, and
passing to the inner and posterior region of the orbit.
XLI.! Remove both eyes: divide one of them into an
inner and an outer hemisphere by an equatorial
incision, Ze. a vertical incision taken at right angles
to and through the centre of a line joining the pupil
and the optic nerve: divide the other into an
anterior and a posterior half by a vertical incision
at right angles to the first, that is passing through
the pupil and entrance of the optic nerve. Note:
343. The fibrous sclerotic, the one-layered choroid,
' As it is necessary to examine the eye while quite fresh, it will
probably be found convenient in practice to substitute an ox’s or sheep’s
eye for the rabbit’s,
THE RABBIT. 331
the retina, the blind spot or entrance of the optic nerve,
the ora serrata, the choroid processes, the lens, the
iris, the pupil, and the aqueous and vitreous humours:
all these have the same essential relations as in the lower
Vertebrata (see p. 84, §§ 224228).
344. The absence of a processus falciformis or
pecten (p. 122, § 179, and p. 250, § 314).
345. The tapetum, a portion of the choroid which,
instead of having the usual black hue, exhibits iridescent
colours.
XLII. Dissect away the parotid gland: clear away the
muscles, &c., from the entire external surface of
the bulla tympani (§ 54): lay open the external
auditory meatus by a longitudinal incision, until
the tubular portion of the tympanic bone is
reached: with bone-forceps cut away very care-
fully and gradually the outer wall of both tubular
and bulbous portions of the tympanic bone,
noting :
346. The tympanic membrane, a transparent fibrous
partition, lying obliquely across the lower end of the
meatus: through it can be indistinctly seen a small bone
—the handle of the malleus (§ 73)—attached to its inner
surface.
347. The cartilage of the pinna, attached to the
tubular portion of the tympanic bone, and with it forming
the external auditory meatus, which thus consists of cartilagin-
ous and osseous portions.
XLIII. Carefully cut away the tympanic membrane so
as not to injure the manubrium mallei, and remove
as much more of the tympanic bone as is necessary
to display the following structures :
348. The tympanum, or tympanic cavity, bounded
332 ZOOTOMY.
internally by the periotic, externally by the tympanic
membrane, below and at the sides by the tympanic bone.
349. The auditory ossicles (see §§ 73—76): after
observing them and their muscles ($$ 352, 353) 2 siu, they
should be removed, and examined under a low power of the
microscope.
350. The fenestra ovalis and fenestra rotunda
($ 56).
351. Tne aperture of the Eustachian tube on the
inner wall of the tympanum, below and anterior to the
fenestra ovalis (see § 55, p. 272, and § 370, p. 336).
352. The tensor tympani, a small muscle inserted by a fine tendon
into the malleus : it arises from the alisphenoid.
353. The stapedius, a still smaller muscle, arising from the surface
of the periotic, just above the fenestra rotunda, and passing forwards to
be inserted into the neck of the stapes,
354. By the removal of the bulla tympani the proximal portions of
the vagus and hypoglossal nerves (§§ 244, 246) are exposed and may be
traced to their foramina of exit from the skull (§§ 43, 58).
355. Lying immediately in front of and parallel to the hypoglossal is
a much slenderer nerve, the glossopharyngeal: it makes its exit from
the skull with the vagus.
356. The spinal accessory or eleventh nerve leaves the skull along
with the glossopharyngeal and vagus, and passes backwards to its
distribution to some of the muscles of the neck.
XLIV. Dissect off the masseter: carefully detach the
ascending portion of the mandible from the
pterygoid muscles which are inserted into its
inner surface: with bone-forceps cut away the
portion of the mandibular ramus lying posterior to
the inferior dental foramen (§ 71): make out :
357. The third division of the fifth or mandibular nerve, supply-
ing the muscles of the lower jaw and sending a branch—the gustatory
nerve—to the tongue: the main trunk is continued through the
inferior dental foramen to the interior of the ramus and so to the
teeth,
THE RABBIT. 333
358. The second division of the fifth or maxillary nerve has
been exposed by the removal of the eye and its muscles, and is seen to
lie on the floor of the orbit: to see it satisfactorily the maxilla must be
gradually broken away : it supplies the upper teeth, and a large branch
passes through the infraorbital foramen (§ 65) to the snout.
XLV. Remove the remainder of the mandibular ramus
of the side on which you are working: dissect
away the pterygoid muscles: pass a probe from the
cut end of the gullet forwards into the mouth: lay
open the gullet along this, and pull the tongue
downwards so as to get a good view of the interior
of the mouth. Note:
359. The transversely-ridged palate (Fig. 64) or roof of
the mouth, continued backwards into a soft membrane, the
velum palati (v/.p2).
360. The tongue (/g), firmly fixed by its postero-inferior
part to the floor of the mouth, presenting on its dorsal
surface a number of small elevations or papillze, and on
each side of its proximal end a small, oval, ridged area, the
papilla foliata.
361. The pharynx, or funnel-shaped posterior ex-
tremity of the mouth, continued backwards into the
gullet.
362. The glottis, an aperture on the floor of the pharynx,
leading, through the larynx, into the trachea. It is guarded
in front by a large flap of cartilage, the epiglottis (egg),
and behind by two small processes of mucous membrane,
the cornicula laryngis (c/a).
363. The aperture of the posterior nares (f.za), an
oval opening in the roof of the pharynx : a probe passed into
it enters the nasal chamber (see § 366).
364. The positions and characters of the teeth (see
§§ 77—80, pp. 277, 278).
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THE RABBIT. 335
The section is taken slightly to the left of the médian plane so as to
clear the mesethmoid (7. et) : all but the anterior and posterior ends of
the septum nasi (m.eth*) is cut away, so as to expose the right nasal cavity
with its turbinals: the brain is removed, so as to show the cranial fossze
and the exits of the nerves through the dura mater (it must be remem-
bered that many of these run for a considerable distance between the
dura mater and the skull before making their exit from the latter) : the
muscles at the base of the tongue are partly dissected away so as to
expose the right sublingual gland (s.¢/). The cartilage is distinguished
by fine, the bone by coarse, dotting.
b.hy, body of hyoid bone: 4.0, basi-occipital: 4.5, basi-sphenoid :
cb.fo, cerebral fossa : cb/.fo, cerebellar fossa: c./a, corniculum laryngis
embedding arytenoid cartilage : cv, cricoid cartilage :¢.t.m, crico-thyroid
membrane: epg, epiglottis: e¢#.4i, ethmo-turbinal: ex, aperture of
Eustachian tube: 7#./0, floccular fossa: fr, frontal: fiv.c, false vocal
cord: g.Ay, genio-hyoid muscle: z.c.a, internal carotid artery: z.Za,
interparietal : 7a, Jacobson’s cartilage: 22, lower incisor: #, masseter
muscle covering edge of mandible: meth, lamina perpendicularis :
m.eth®, septum nasi: x, mandibular symphysis: mo, mouth cavity :
mx, palatine plate of maxilla: mx./b, maxillo-turbinal: za, nasal:
na.tb, naso-turbinal : oc.at.m, occipito-atlantal membrane : od, odontoid
process : es, cesophagus : o/.fo, olfactory fossa: ga, parietal : 2/, palatine
plate of palatine: pmx, premaxilla: Z.2a, posterior nares: f.s, pre-
sphenoid: s.g, sublingual gland: s.mx, submaxillary gland: s.o,
supra occipital: sf.1, 5f.2, sf.3, roots of first three spinal nerves :
st.hy, sterno-hyoid muscle: s.¢, sella turcica : ¢g, tongue: 7h, thyroid
cartilage : ¢z, tentorium : ¢r, trachea: w.7', anterior, and z.2°, posterior,
upper incisor: v1, atlas; v2, centrum, and v.2’, arch of axis:
v.3, v.3', of third vertebra: vc, vocal cords: v./, ventricles of larynx :
vi.pa, velum palati: vr.a, vertebral artery: 2, bristle passed through
right nostril: y, bristle passed through right naso-palatine canal:
LI—XTf, roots of cerebral nerves.
365. The small paired aperture of the naso-palatine or
Stenson’s canals (¥), situated immediately behind the
posterior upper incisors (z.2?), and leading into the nasal
chamber.
XLVI. Remove the nasal, and enough of the pre-
maxilla and maxilla to show:
366. The ethmo-, maxillo-, and naso-turbinals
(eth.tb, mx.th, na.tb, §§ 61, 63, 66, pp. 274, 275), and their
relations to the nasal chamber in which they are contained.
367. The delicate, reddish-brown, mucous membrane
(Schneiderian membrane) lining the nasal chamber and
336 ZOOTOMY.
covering the turbinals: that on the ethmo-turbinals is dis-
tinguished as the olfactory mucous membrane.
368. The olfactory nerves, given off from the olfactory
lobes to the olfactory mucous membrane: the maxilo-
turbinals are supplied by the maxillary nerves.
XLVII. Pass a probe from the anterior nostril into the
nasal chamber as far backwards as it will go:
remove the turbinals and as much of the maxilla
and palatine as is necessary to show
369. The backward continuation of the nasal chamber to
the posterior nares.
370. The aperture of the Eustachian tube (ex), in
the dorsal wall of the posterior nasal passage, a little anterior
to the posterior nares: a probe should be passed through
the tube from its aperture in the tympanum (§ 351).
371. The septum nasi (w-.eth®, § 59), forming a median
vertical partition between the anterior part of the two nasal
chambers.
372. Jacobson’s cartilage (jz, § 60), lying immediately external
to the ventral edge of the septum nasi and ensheathed by the palatine
process of the premaxilla: it has the form of a cylinder with
tapering ends.
373. Jacobson’s organ, seen by carefully removing the palatine
process of the premaxilla and Jacobson’s cartilage: it consists of a deli-
cate tube of mucous membrane, inclosed in the scroll-like Jacobson’s
cartilage, and opening at its anterior end into the nasal chamber. It is
supplied by branches of the olfactory nerve which pass downwards and
forwards along the surface of the septum nasi.
XLVILI. Remove the larynx with the anterior part of the trachea,
and dissect away the muscles, &c., attaching them to surround-
ing parts. If only one larynx is to be had, make a longitudinal
vertical section of it, keep one half entire, and from the other
dissect away the muscles and mucous membrane so as to see
the cartilages clearly, If two specimens are to be had, clean
the cartilages of one, and use the other for the soft parts,
making a longitudinal section of it when necessary (at § 379).
THE RABBIT. 337
Examine first the cartilages and then the soft parts, making
out:
374. The thyroid (Fig. 64, 4h), a large plate of cartilage, consisting
of right and left ala united to one another ventrally at an obtuse
angle: dorsally each alx is produced into anterior and posterior
cornua, small processes, the posterior of which articulates with a facet
on the cricoid.
375. The cricoid (cv), an annular cartilage, narrow ventrally, wide
dorsally, situated immediately behind the thyroid, the posterior cornua
of which articulate with facets on the dorso-lateral regions of its outer
surface ; ventrally there is a considerable interval between the thyroid
and the cricoid, bridged over by the crico-thyroid membrane
(er.th.m).
The anterior ring of the trachea is often more or less transitional
between the ordinary tracheal rings and the cricoid.
376. The arytenoids (ary), paired triangular cartilages articulated
to facets in the postero-dorsal region of the anterior edge of the
cricoid.
377. The cartilage of Santorini, small paired nodules embedded in
the cornicula laryngis (¢./2).
378. The epiglottis (efg), an obcordate plate of cartilage attached
by its narrow ventral end to a facet on the inner surface of the ventral
region of the thyroid.
379. The reddish mucous membrane lining the larynx, continuous
behind with that of the trachea and in front with that of the pharynx.
380. The ventricles of the larynx (v./a), paired shallow de-
pressions on its inner surface at about the level of the arytenoids,
381. The vocal cords (v.c), paired folds of mucous membrane
forming the posterior boundaries of the two ventricles and supported by
ligaments : they extend from the arytenoids downwards to the inner face
of the thyroid, where they are attached close together just posterior to the
facet for the epiglottis.
382. The false vocal cords (/-v.c), similar folds forming the anterior
boundaries of the ventricles.
383. The crico-thyroid muscles, arising one on each side from the
outer surface of the cricoid, and passing forwards and upwards to be
inserted into the thyroid, which they serve to depress.
384. The posterior crico-arytenoid muscles, large paired muscles
covering the dorsal surface of the cricoid, from which they arise, and
passing outwards and forwards to be inserted into the arytenoids.
385. The arytenoid muscles, situated immediately anterior to the
Z
338 ZOOTOMY.
crico-arytenoids, and consisting of fibres passing transversely between the
arytenoid cartilages, which are approximated by their contraction.
386. The anterior crico-arytenoid muscles, arising from the
lateral regions of the cricoid and inserted into the arytenoids: to see
them one of the ale of the thyroid should be disarticulated and
reflected.
387. The thyro-arytenoid muscles, also seen by reflection of the
thyroid: they run parallel and external to the vocal cords, arising
from the arytenoids and being inserted into the thyroid, which they
elevate.
XLIX. Dissect away enough of the muscles in the
regions of the shoulder and hip to make out :
388. The brachial plexus, formed by the union of the
fifth to eighth cervical and of the first thoracic nerves,’ and
giving off nerves to the arm and shoulder.
Besides several smaller nerves there are four chief trunks given
off from the brachial plexus :? (a) the ulnar nerve runs alongside the
brachial artery, passes immediately internal to the olecranon into the
fore-arm, and then along the outer or ulnar side of the latter: (4) the
median netve passes internal to the humerus, entering the fore-arm
proximal to the condyles, and takes a course along the inner or radial
side of the fore-arm; both it and the ulnar nerve supply maiuly the
flexor muscles: (c) the musculo-spiral nerve, the largest of the four,
goes to the dorsal side of the humerus and along the radial side of the
fore-arm ; it supplies mainly the extensor muscles: (¢) the circumflex
or subscapular nerve passes dorsalwards round the head of the
humerus and supplies some of the muscles of the shoulder.
389. The lumbo-sacral plexus, formed by the
union of the fifth to seventh lumbar and of the first to
1 There is a certain ambiguity in the usual mode of counting the
spinal nerves: in the cervical region each nerve is named from the
vertebra in front of which it emerges, the first or sub-occipital nerve
coming out between the skull and the atlas, the eighth between the
seventh cervical and first thoracic vertebra : the remaining nerves are
named from the vertebrae behind which they emerge: the first thoracic,
for instance, is the nerve which makes its exit between the first and
second thoracic vertebree,
* If the muscles of the arm are to be dissected in the same specimen,
the tracing of these nerves must be deferred,
THE RABBIT. 339
third sacral nerves, and giving off branches to the leg
and hip.
Three chief nerves arise from the lumbo-sacral plexus: (a) the crural
nerve, passing out ventral to the pelvis and supplying the extensor
(anterior) muscles of the thigh: (4) the obturator nerve, passing along
the inner edge of the pubis and through the obturator foramen : and (c)
the sciatic nerve, the largest of the three, passing out between the
ischium and the sacrum and going mainly to the flexor muscles.?
L. Remove the skin from the back and limbs, and make
out the following muscles : 2
390. The dorso-lumbar fascia, a strong sheet of
connective tissue which covers all but the most superficial
muscles of the back: it is continuous in front with the
cervical fascia.
391. The trapezius (Fig. 65, A, ¢z), a thin superficial
sheet of muscle extending over a great part of the dorsal
aspect of the cervical and thoracic regions: it arises in the
middle dorsal line from the cervical and thoracic fasciz : the
fibres of its anterior part pass backwards and outwards, and
are inserted into the metacromion (§ 81), those of its
posterior portion pass forwards and somewhat outwards, and
are inserted into the dorsal half of the spine of the scapula.
392. The latissimus dorsi (/d), an extensive sheet of
muscle arising partly from the dorso-lumbar fascia, partly
from the three posterior ribs by as many triangular slips or
digitations, which fit between or interdigitate with
similar slips of the external oblique (§ 139): in its posterior
part it is united with and scarcely distinguishable from the
1 Tf the muscles of the leg are to be dissected in the same specimen,
the tracing of these nerves must be deferred.
2 It is advisable to have another specimen, well hardened in alcohol,
for the muscles, as many of those described will have been destroyed by
the previous dissection,
Z2
340 ZOOTOMY.
Fic. 65, A.—Lepus cuniculus. Muscles of the fore-limb, from
the outer side (x 4).
ab.p, abductor pollicis : a.67.2, abductor brachii inferior: a@.67.5, ab-
ductor brachii superior : az. /, annular ligament : 4.4%, basio-humeralis:
di, biceps : 47.2, brachialis internus : c/. 7, cleido-mastoid : cp./, capsular
ligament of shoulder : v.67, coraco-brachialis: d¢, deltoid : ex.c.d, ex-
tensor communis digitorum: ex.cf.7, extensor carpi radialis : ex.cp.u,
extensor carpi ulnaris : ex.d.4, extensor quarti digiti: ex.d.5, extensor
quinti digiti: ex.f.@, extensor parvus antibrachii: /7.c/.7, flexor carpi
radialis: /Z.cf.z, flexor carpi ulnaris: /7.4.d}, superficial head of flexor
profundus digitorum, its middle portion removed to show the underlying
muscles (C): #.2.d%, ulnar head of the same muscle: /7..@3, its radial
head : f.p.@4, its middle head: 7.5 d, flexor sublimis digitorum: Ax,
humerus : 7.5.f, infra-spinous fascia: ¢/.a, linea alba: /.a.sc, levator
anguli scapulz: Zd, latissimus dorsi: /.sc.m, levator scapulze major :
ob.ex, obliquus externus abdominis : fc.ma, pectoralis major: pc.mz,
pectoralis minor : gc.¢, pectoralis tenuis : A/, palmaris: f7.c, panniculus
carnosus: 7.7, pronator teres : 7.ad, rectus abdominis: 74.c, rhomboideus
cervicalis : rh.d, rhomboideus dorsalis: sy.#, serratus magnus: 5.5¢,
subscapularis : s.sf, supra-spinatus : s.s9.f, supra-spihous fascia : s¢.2y,
sterno-hyoid : s¢.m, sterno-mastoid: ¢e.ma, teres major: zr, trachea:
tr’, middle, 4°, external, 73, internal, and ¢4, accessory, head of triceps:
tz, trapezius : 2/, ulna,
THE RABBIT. 341
trapezius : its fibres are gathered into a comparatively narrow
bundle and inserted into the humerus.
393. The levator scapulz major (/.sc.m), anarrow band,
arising from the base of the skull, and passing backwards
parallel and close to the antero-external border of the
trapezius, to be inserted with the latter into the met-
acromion.
clan stm
STM ober rab
Fic. 65, B.—Lepus cuniculus. Muscles of the fore-limb, from the
ventral aspect (x 4). For references see Fig. 65, A.
394. The cleido-mastoid (Fig. 65, A and B, cm),
arising with the sterno-mastoid (stm, § 130), from the
periotic, and passing backward to be inserted into the
clavicle.
395. The basio-humeralis (d.4z), lying dorsal to the
sterno- and cleido-mastoid : it arises from the basioccipital,
and passes backwards and outwards to be inserted into the
outer third of the clavicle.
396. The deltoid (d), a somewhat triangular muscle
covering the point of the shoulder : it arises from the outer
342 ZOOTOMY.
half of the clavicle, and is inserted into the deltoid ridge
of the humerus, its insertion covering that of the pectoralis
(§ 131).
LI. Cut through the trapezius, latissimus, and levator
scapula major near their insertions, and reflect them
so as to expose the underlying muscles: note:
rhe
{ 8.8L
barat "
thd nD SSP te.ma| La.se
Fic. 65, C.—Lepus cuniculus. Muscles of the fore-limb, from the
inner side (x 4). For references see Fig. 65, A.
397. The rhomboideus dorsalis (Fig. 65, C, r/.a),
a squarish muscle, arising from the spines of the anterior
thoracic vertebrae, and passing outwards to be inserted into
the supra-scapular border of the scapula (§ 81).
398. The rhomboideus cervicalis (r.c), a long
muscle arising from the hinder surface of the skull and
THE RABBIT. 343
from the spines of the cervical vertebrae, and inserted with
the preceding muscle into the supra-scapular border.
399. The serratus magnus (A, B, and C, srm), a
somewhat quadrate muscle arising from the third to ninth ver-
tebral ribs near their junctions with the sternal ribs by seven
slips which interdigitate with the external oblique : its fibres
pass upwards and forwards, and are inserted into the
supra-scapular border.
4oo. The levator anguli scapule (/a.sc), a large
muscle arising from the transverse processes of the last five
cervical vertebrae, and passing backwards to be inserted into
the inner surface of the scapula close to its supra-scapular
border.
401. The pectoral muscles have already been seen
(p- 290 §§ 131—133); the insertion of the pectoralis
minor can now be conveniently made out: the muscle
passes dorsalwards, beneath (posterior to) the clavicle, into
which some of its fibres are inserted, and then spreads out
into a broad sheet which covers the anterior region of the
scapula, and is inserted into the pre-scapular fascia,
which invests the remaining muscles in the pre-scapular
fossa.
402. The erector spine, a complicated, longitudinal
muscle, forming with its fellow the ridge of the back, and
serving as the chief straightener of the vertebral column.
403. The abductor brachii superior (a.d7.s), a small
triangular muscle arising from the acromion, and inserted
into the deltoid ridge: detach from its origin and reflect.
LII. Cut through the insertions of the pectoralis minor,
rhomboidei, serratus magnus, and levator anguli
scapula: cut through the ligament joining the
clavicle to the scapula, and so detach the fore-limb
with the scapula from the trunk. Dissect out:
344 ZOOTOMY.
On the inner surface of the scapula.
4o4. The teres major (¢e.ma), a stout muscle arising
from the greater part of the glenoid border of the scapula,
and inserted into the shaft of the humerus near the insertion
of the latissimus: cut it through the middle and reflect
both ends.
40s. The subscapularis (s.sc) a large flat muscle arising
from the whole of the subscapular fossa, and inserted into
the lesser tuberosity of the humerus: detach from its origin
and reflect.
406. The coraco-brachialis (cdr), a small muscle
covering the insertion of the subscapularis: it arises from
the coracoid, and is inserted into the proximal end of the
shaft of the humerus: cut through and reflect.
On the outer surface of the scapula.
407. The supra-spinatus (s.sf), arising from the whole
of the pre-scapular fossa and pre-axial surface of the spine of
the scapula, and inserted into the upper margin of the
greater tuberosity of the humerus: detach from its origin
and reflect.
408. The abductor brachii inferior (a.d7.2) arising
from the infra-sspinous fascia (sf) or connective
tissue covering the infra-spinatus ($ 409), as well as from
the acromion and metacromion: it passes beneath the
latter and is inserted into the outer face of the humerus
just distal to its head: detach from its origin and reflect,
removing with it the metacromion.
409. The infra-spinatus (7.sf), lies beneath the pre-
ceding: it arises from the whole post-scapular fossa and
from the post-axial surface of the spina scapule, passes
beneath the acromion, and is inserted into the greater
tuberosity of the humerus: detach from its origin and
reflect.
THE RABBIT. 345
410. The teres minor, a small muscle exposed by the
removal of the preceding: it arises from the ventral third of
the glenoid border of the scapula, and is inserted into the
greater tuberosity just below the insertion of the infra-
spinatus.
In the upper arm.
411. The extensor parvus antibrachii (ex.g.a), a
small flat muscle lying on the inner face of the upper arm
about midway between its anterior and posterior borders:
it arises by a flat tendon from the fascia of the upper arm,
and is inserted into the olecranon: cut it through and
reflect.
412. The triceps, or chief extensor of the fore-arm:
a very large muscle consisting of four parts or heads—
(2). The middle or long head (anconeus longus, 77"),
a large fleshy mass forming the posterior edge of the upper
arm : it arises from the ventral third of the glenoid border
of the scapula, and is inserted into the olecranon: divide
and reflect.
(2). The short or outer head (anconeus brevis, #*)
is situated on the outer face of the upper arm just in front
of the preceding: it arises from the outer surface of the
shaft of the humerus, and is inserted with the long head into
the olecranon: detach from its origin and reflect.
(c). The inner head (anconeus internus, ¢*) occupies
a similar position on the inner face of the upper arm, lying
between the anconeus longus and the biceps (§ 413}: it.
arises from the posterior surface of the shaft of the humerus,
and is inserted into the olecranon: detach from its origin
and reflect.
(d). The accessory head (anconeus quartus, 77+) is a
very small, fan-shaped muscle, exposed by reflection of the
anconeus longus and internus, on the inner faee of the
346 ZOOTOMY.
elbow-joint : it arises from the inner condyle of the humerus,
and is inserted into the olecranon.
413. The biceps brachii (27), or chief flexor of the
fore-arm: a spindle-shaped muscle forming the anterior
edge of the upper arm: it arises by a single cord-like
tendon, working in the bicipital groove of the humerus,
from the anterior edge of the glenoid cavity, and is in-
serted into the proximal end of the radius: cut it through
and reflect.
414. The brachialis internus (47.7), a flattish muscle
lying on the outer face of the upper arm between the an-
coneus brevis and the biceps: it arises from the outer
surface of the proximal portion of the shaft of the humerus
and is inserted into the radius just proximal to the insertion
of the biceps
Ln the forearm and hand.
415. The extensor carpi radialis (Figs. 65, A and C,
and 66, ex.cp.r), or chief extensor of the entire hand, a long
muscle forming the anterior edge of the fore-arm: it arises
from the outer condyle of the humerus: its distal end divides
into the slender tendons which pass beneath the tendon
of the abductor pollicis ($ 418), and then under the annu-
lar ligament (az./), a transverse fibrous band at the junc-
tion of the fore-arm and hand, and are inserted into the
proximal ends of the second and third metacarpals: cut
through and reflect.
416. The extensor communis digitorum (ex.¢.d), or
principal extensor of the fingers, a long muscle situated on
the external and dorsal surface of the fore-arm in the groove
between the radius and ulna: it arises from the outer con-
dyle of the humerus, and at the distal end of the fore-arm
divides into four tendons which pass beneath the annular
ligament to the four post-axial digits. Fach tendon passes
THE RABBIT. 347
along the dorsal aspect of the corresponding digit, broadens
out into a sort of sheath over the metacarpo-phalangeal
Fic. 66.—Lepus cuniculus. Muscles of the manus. A, dorsal ;
B, ventral (nat. size). :
I—5, the digits: aé.d.5, abductor minimi digiti: @d.¢, abductor
pollicis : az./, annular ligament : ex.c.d, extensor communis digitorum :
ex.cp.r, extensor carpi radialis : ex.cp.u, extensor carpi ulnaris: ex.d.4,
extensor quarti digiti: ex.d.5, extensor quinti digiti; ex..2, extensor
pollicis et indicis: 7,f.d.m, flexor brevis minimi digiti: 7.2.2, flexor
brevis pollicis : #.cp.r, flexor carpi radialis : 2.cf., flexor carpi ulnaris :
Jfi.p.d, flexor profundus digitorum : 72..d, its tendon to the index digit,
cut short: 72.s.d, flexor sublimis digitorum: /.s.d*, its tendon to the
second digit partly removed, and its distal end reflected: 7.5.d4, its
tendon to the fourth digit partly removed, and having the sheath it forms
over the metacarpo-phalangeal articulation cut through and reflected
right and left: zo, interossei: 7.1, /4.2, /6.3, lumbricales: + (above),
radius : x (below), retinacula, those of the second digit cut through and
reflected to show the insertion of the flexor sublimis : z, ulna.
348 ZOOTOMY.
and inter-phalangeal articulations, and is inserted into the
middle and distal phalanges: divide and reflect.
417. The extensor pollicis et indicis (ex.p.2), a
small, slender muscle lying in the groove between the radius
and ulna, beneath the common extensor: it arises from
the radius: its tendon enters the manus along with that
of the extensor communis, and divides into two, one of
which is inserted into the ungual phalanx of the pollex, the
other into the distal end of the metacarpal of the index.
418. The abductor pollicis (aé.f), arising from the
outer surface of the shaft of the radius: its tendon crosses
that of the extensor carpi radialis, and is inserted into the
metacarpal of the pollex.
41g. The extensor quarti digiti (ex.d.4), the extensor
quinti digiti (ev.d.5), and the extensor carpi ulnaris
(ex.cp.u), three small, slender muscles arising close together
from the external condyle of the humerus, and passing
backwards behind the ulna to the manus. The extensor
quarti digiti is inserted into the ungual phalanx of the fourth
digit, the extensor quinti digiti into the base of the meta-
carpal and the proximal phalanx of the fifth digit, and the
extensor carpi ulnaris into the proximal end of the fifth
metacarpal: cut through and reflect all three muscles.
420. The flexor carpi ulnaris (/.¢.u), forming the
posterior edge of the fore-arm: it arises by an expanded
head from the inner face of the olecranon, and is inserted
into the pisiform: divide and reflect.
421. The pronator teres (Fig. 65, C, #.¢), a small muscle
arising from the inner condyle of the humerus, and inserted
by a long tendon into the middle of the inner side of the
shaft of the radius.
422, The flexor carpi radialis (/.