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A COURSE OF INSTRUCTION

IN

ZOOTOMY.

(VERTEBRATA.)

A COURSE OF INSTRUCTION

IX

ZOOTOMY.

(VERTEBRA TA.}

BY

•

T. JEFFERY PARKER, B.Sc. LOND.

PROFESSOR OF BIOLOGY IN THE UNIVERSITY OF OTAGO. NEW ZEALAND.

WITH SEVENTY-FOUR ILLUSTRATIONS.

JT0itbon :
MACMILLAN AND CO.

1884.

The Right of Translation and Reproduction is reserved.

LONDON :

R. CI.AV, SONS, AND TAYLOR,

BREAD STREET HILL. E C.

o

TO

MY FRIEND AND CRITIC,

C. E. R. P.,

ijjis

PREFACE.

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 Elementary Biology, and aim at being a continuation
of the zoological part of that work, in much the same way
as the Practical Physiology 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 Elementary 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 (Phil. Trans. 1879), and Fig. 38 from
Herpetologia Europaa ; 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.

T. J. P.

OTAGO UNIVERSITY MUSEUM,
DUNEDIN, N.Z.

June, 1883.

CONTENTS.

PAGE

PREFACE ... vii

LIST OF WOODCUTS xiii

INTRODUCTION . xvii

THE LAMPREY—

A. The Skeleton . . I

B. Directions for Dissection .... 8

THE SKATE —

A. The Skeleton 27

B. Directions for Dissection 40

C. Special Dissection of the Nervous System and Sense

Organs 69

THE COD—

A. The Skeleton 86

B. Directions for Dissection 101

THE LIZARD—

A. The Skeleton 130

B. Directions for Dissection 153

xii CONTENTS.

THE PIGEON — PAGE

A. The Skeleton 182

B. Directions for Dissection 209

THE RABBIT —

A. The Skeleton 262

B. Directions for Dissection 286

WORKS OF REFERENCE „ . . .381

INDEX . 384

LIST OF WOODCUTS.

FK;. PAGE

1 . Petromyzon marinus. The skull, from the left side .... 3

2. The brain-case, from above 4

3. The nasal capsule 5

4. Dissection of the anterior part of the body, from the

left side 9

5. The urinogenital sinus and adjacent pans n

6. Transverse section through the branchial region .... 12

7. Transverse section through the abdominal region ... 14

8. Transverse section through the caudal region .... 17

9. The brain, from above 24

10. Raja nasuta. The skeleton, from beneath 30

11. Part of the vertebral column 31

12. A trunk vertebra, from the front 32

13. Longitudinal section of trunk vertebra 33

14. A caudal vertebra, from the front 34

15. The gall-bladder and bile-ducts 49

1 6. The portal vein 51

17. The venous system 53

1 8. Raja batis. Urinogenital organs (male) 55

19. Urinogenital organs (female) .... 57

20. Raja nasuta. The arterial system 62

21. Diagram of the heart and chief blood-vessels 63

o

22. The nervous system, from above 71

23. Raja batis. The brain, from beneath .... 73

24. Longitudinal section of the brain .... 74

25. The brain, from the left side •• • 74

26. Raja nasuta. Roots of the fifth, seventh, and eighth nerves 75

xiv LIST OF WOODCUTS.

FIG. PAGE

27. Raja nasuta. Principal branches of the fifth, seventh, and

eighth nerves . . 75

28. Raja balls. The auditory organ 8 1

29. Gadus morrkua. Side view of a disarticulated skull ... 92

30. The superficial muscles and nerves 104

31. The alimentary canal 108

32. The vascular system 117

33. The auditory organ 123

34. The brain 125

35. Lacerta agilis. Longitudinal section of the skull 137

36. The columellj. auris 142

37. The chondrc cranium, from above 144

(Lacerta viridis. \ ^
fy T ... Outline oi the head in the three species,

38. \ Lacerta aeihs. . . .

„ . . showing the epidermic scales .... ICC
V Zootoca mmpara . )

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 60

41. Urinogenital organs (male) 166

42. Urinogenital organs (female) 167

43. The heart, dorsal aspect 172

44. The aortic arches 173

45. The brain 177

46. Columba lima. 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

51. Tarso-metatarsus of an unhatched embryo 207

52. Urinogenital organs (male) 228

53. Urinogenital organs (female) 230

54. The circulatory system 232

55. The cloaca 236

56. The heart, from th^dorsal aspect 241

57. The lungs and syrinx 245

58. The brain 255

59. Dissections of the brain 259

60. Lepus cuniculus. Part of the alimentary canal with the

portal system and bile-ducts 301

61. The vascular system 309

62. Urinogenital organs (male and female), from the side . 317

LIST OF WOODCUTS. xv

FIG. PAGE

63. Lepus cztnicnlus. Part of the female organs, ventral aspect . 322

64. Longitudinal section of the head 334

65. Muscles of the fore limb—

A. From the outer side 340

B. From the ventral aspect 341

C. From the inner side 342

66. Muscles of the rnanus 347

67. Muscles of the hind limb, inner side 352

68. Muscles of the hind limb, outer side 355

69. Muscles of the pes 361

70. The brain, from beneath 367

71. Dissections of the brain, from above 371

72. Longitudinal section of the brain 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," i.e. a blunt bent needle fixed in a handle.
A German silver anatomical blowpipe.1
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 ;
C. 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, in, 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 cannuke 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 cannulae 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.

c. 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 ; l 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,1 or
boro-glycerine.

I should strongly advise students to adopt the plan so
much insisted upon by Professors Huxley and Martin in
their Elementary 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 I '2 litre of glycerine
and 0*3 litre of methylated alcohol.

ZOOTOMY

THE LAMPREY.

THE SEA LAMPREY (Petromyzon 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 for 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
<E 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 . . . . 10 parts.

Water . . . . 10 ,,

Corrosive sublimate . . 0*1 „
Alum .... 0-2 .,

(b) Transfer to melted glycerine jelly made by
dissolving 2 parts of gelatine, or " gelatin.6 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.

II. In the prepared skeleton make out the following
points :-

1. The notochord (Fig. i, nc), 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, nc).

2. The neural processes (Fig. i and 6 «./), small rods
of cartilage, set in pairs at short intervals along the dorso-lateral
regions of the notochord, and partly inclosing the neural
canal (Figs. 4 and 6 — 8, n.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, /./).

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4 ZOOTOMY.

3. The fin-rays (Figs. 7 and 8,/r), 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, i and 2, b.pt b.p'), surrounding the anterior end of
the notochord, and divided by the latter into dorsal (b.p)
and ventral (b.p') portions. The ventral portion forms a
continuous plate beneath the anterior end of the notochord
(Figs. 2 and 4, b.p') ; the dorsal portion consists of two

aa.

FIG. 2. — Petromyzon marinus. The brain case, from above, the
subocular arches supposed to be removed (nat, size : from a larger
specimen than Fig. i).

mi, auditory capsules : b.p, dorsal, and b.p', ventral portion of
basal or parachordal plate : h.p, hard palate : na.p, naso-palatine
canal : oc, occipital arch : tr, 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 trabeculse (Fig. 2, tr\ which unite
with one another in front, forming the hard palate (h.p\
and inclosing an oval space, the naso-palatine canal
(na.p}. Laterally, the trabeculae and hard palate send up
plates of cartilage (w)t 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 (p.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, i and 2, an\ 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. i, na ; 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

FIG. 3. — Petromyzon marinus. The nasal capsule, front view (nat.

size). I, olfactory foramina.

cavity (see Fig. 4 na.c). Near its centre it is perforated by
two oval apertures (Fig. 3, i) for the passage of the
olfactory nerves.

7. The subocular arches, each consisting of an
anterior lateral process (Fig. i, <?././), springing from
the anterior end of the hard palate, and of a posterior
lateral process (p.l.p), 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. i, st.fl), cylindrical
rods springing one from the posterior edge of each posterior
lateral process, near its proximal end, and taking a directly
downward course.

6 ZOO TOM Y.

9. The cornual cartilages (Fig. i, c.c\ small, irregular,
horizontal pieces, connected by fibrous tissue to the distal
ends of the styliform processes.

10. The posterior dorsal cartilage (Figs, i and 4,
p.d\ 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, i and 4,
a.d), 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. i, a. I),
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. i, /./),
flattened plates, situated one on either side beneath the pos-
terior dorsal cartilage, and between the descending process
of the anterior dorsal caitilage, and the anterior lateral
process of the subocular arch.

14. The lingual cartilage (Figs, i and 4, Ig), 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 (lg*} having the
form of a semicircle, and set transversely : with the free,
upwardly directed ends of this are connected two small
irregular cartilages (lg"}. The lingual cartilage lies in the
floor of the mouth ; the semicircular cartilage (lg'} sup-
ports the median portion of the tongue ; the small cartilages
(/£•") lie in the lateral wings of the tongue (§ 23,
Fig. 4, /,/').

15. The median ventral cartilage (Figs, i and 4,

THE LAMPREY. 7

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, i and 4, an\ a stout
circular cartilage, supporting the oral funnel (§ 21), and
giving attachment to the maxillary and mandibular teeth

o o »

(§ 24).

17. The styliform cartilages (Fig. i, st\ 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.

1 8. The branchial basket (Fig. i, d.c, i'.c, a — k, pc\
a cartilaginous framework supporting the gills. It consists
essentially, on each side, of (i) a longitudinal rod or dorsal
cartilage (d.c\ springing from the dorsal portion of the para-
chordal (&/), 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 — £•, k) uniting the dorsal
and ventral cartilages and passing between the outer gill-
clefts ; (4) lateral longitudinal bars (//, i) connecting the
transverse arches immediately above and immediately below
the gill-clefts; and (5) a cartilage (pc] supporting the
posterior and lateral walls of the pericardium.

Each of the transverse arche?, 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 (b] and sixth (/) are short curved rods ; the third (c) and fifth
(e) are flattened, and are produced into forwardly directed processes j
the fourth or middle portion (d) is a curved rod situated immediately

f

8 ZOOTOMY.

behind the corresponding gill-cleft. The longitudinal connecting bars
(k and i) 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 (k).
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 (st.p). 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 (pc). The latter has the
form of a backwardly directed hemispherical 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, h, z), so that they are seen at once when those muscles are removed :
but the pieces marked b, 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.

21. 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
papillae, passes insensibly into the general surface of the

1 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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io ZOOTOMY.

body above and at the sides, while below it is separated by
a deep furrow (Fig. 4, gr).

22. The mouth (Fig. 4, ;//), situated at the bottom of
the oral funnel, and of a somewhat crescentic form.

23. The tongue (Fig. 4, /), 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 (t).

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,
e.a), 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, #.#./),, 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 (s), — 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 diphy cereal, that is, evenly distributed
above and below the axis of the tail.

Ult

FIG. 5. — Petromyzon marinus. The urinogenital sinus, with the
rectum and part of the left kidney (nat. size).

#, anus : tnt, intestine : k, left kidney : r^ rectum : tt.g.p, urino-
genital papilla : u.g.s, urinogenital sinus : ?er, left ureter, .r, aper-
ture of left, and x' aperture of right ureter into urinogenital sinus :
y, bristle passed through right abdominal pore : c, 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 to a
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, i.e. at right angles to the general direction
of the myotomes themselves.

oes

FIG. 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.

br.w., branchial membrane: d.ao, dorsal aorta: d.c, dorsal carti-
lage of branchial basket : d.m, dorsal body-muscles : e.a, external
branchial aperture : f.t, fibrous tissue -inclosing neural canal : //, i,
lateral longitudinal cartilages of branchial basket : i.a, internal branchial
aperture : i.ju, inferior jugular vein : ///, jugular vein : my, myelon :
nc, notochord : n.ca, neural canal : u.f>, neural processes : as, oeso-
phagus : p.br, peri-branchial sinus : r.m.t, retractor muscle of tongue :
r.t, respiratory tube : s, circum-oesophageal sinus : v.ao, ventral aorta;
v.c, ventral cartilage of branchial basket : v.m, 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 alongish 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, lr\ 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 dorsally 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 :

ZOOTOMY.

the testis is a soft, greatly tabulated organ, closely resembling
fat : the ovary (Fig. 4, or\ 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.

m

-n.ca

f*

v*t

ur

int

FIG. 7. — Petromyzon marinus. Transverse section through the
abdominal region, including the first dorsal fin (nat. size).

cd, cardinal veins : d.ao, dorsal aorta : f.r, fin rays :, f.t, fibrous
tissue inclosing neural canal : int, intestine, the line pointing to the
spiral valve : k, kidneys : ly, sub-vertebral lymph sinus : m, body-
muscles : my, myelon : nc, notochord : n.ca, neural canal : ts, testis :
ur, ureter.

39. The intestine (Figs. 4 and 7, /'«/), 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, £), 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, ?/;•), 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, ii.g.s), a small
ovoidal sac, lying close behind the rectum, and becoming
narrowed ventrally to form the urinogenital papilla
(u.g.p).

43. The sub-vertebral lymph sinus (Fig. 7, /j-), ,1 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, pc), lying just
in front of and partly covered by the liver : its almost
hemispherical posterior wall, strengthened by cartilage
(§ 1 8, Fig. I, pc) 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 T by the external
aperture : observe—

45. The apertures of the ureters (Fig. 5, x, x'), 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, int), a longitudinal fold of
mucous membrane, projecting into the cavity of the intestine, and
having a slight spiral twist.

48. The aperture of the resophagus (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. rnarinu?, the aperture of the bile duct (Fig. 4, b.d), 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, cd\ 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, d.ao\ 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. 17

be formed by the bifurcation of a single trunk, the caudal vein (Fig.
8, c.v), which may be traced to the end of the tail, lying to the ventral
side of the caudal artery (Fig. 8, c.a), which is the direct continua-
tion of the dorsal aorta.

Ti.ca

c.v.

FIG. 8. — Petromyzon marinus. Transverse section through caudal
region, including the second dorsal fin (nat. size).

. c.a, caudal artery : c.vy caudal vein : f.r, fin rays : _/./, f.t', fibrous
tissue enclosing neural canal : m, body-muscles : my, myelon : ;/<-,
notochorcl : n.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 br, 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 —

c

iS 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, La), on the inner walls of the gill-sacs, leading into the
respiratory tube presently to be seen (§ 58).

56. The peribranchial sinuses (Fig. 6, p.br], 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.f), surrounding the lingual cartilage (§ 14, Figs, i
and 4, /£-), 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, r.t), lying almost immediately above the retractor
of the tongue l : the seven internal branchial apertures of
the left side are seen perforating its lateral wall.

59. The oesophagus (Figs. 4 and 6, as), 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), is 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
is1 related to the gullet like a 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 body-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 oesopha-
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, m\ com-
municating with the oral funnel by the very narrow oral
aperture.

65. The oral caecum, a blind pouch of the mucous membrane in
about the middle of the mouth-cavity, on the dorsal side (Fig 4, m) ;
it is continued posteriorly into a longitudinal groove.

66. The aperture of the oesophagus (Fig. 4, between
m and ces), 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, vl).

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.

XIII. Open the pericardium by carefully removing the
greater part of its left wall : note

69. The auricle (Fig. 4, au), 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.

70. The ventricle (Fig. 4, z1), seen by lifting up the
auricle to lie towards the right side of the pericardium : it
his 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. r.ao), 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 (i.e.
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-oac.

73. The inferior jugular vein (Fig. 4, i.ju) 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.ad), 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 proba 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, jit], 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.

So. The hepatic vein (Fig. 4, /$.?') may also be seen at this
stage ; leaving the liver, it pierces the pericardium and enters the
sinus venosus at the same 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 rnyelon (Figs. 4,
6 — 8, my, and 9), lying loosely in the neural canal (n.ca),
and passing in front into the brain (Figs. 4 br, and 9),
which nearly fills the small cranial cavity.

84. The medulla oblongata or myelencephalon
(Fig. 9, M.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

("'• 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, d>).

86. The mid-brain, or mesencephalon (Fig. 9, o.l}>
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,
///), 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
continuous behind with the aqueduct of Sylvius,

24 ZOOTOMV.

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, c.h\ the larger anterior part to olfactory
lobes, or rhinencephala (olf).

89. The nasal sac (Fig. 4, na), 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.

S.C

S.C

FIG. 9. — Petromyzon marinus. The brain from the dorsal aspect,
with the right auditory sac (X 3).

aq.s, aqueduct of Sylvius : a.s.c, anterior semicircular canal : cb,
cerebellum : c./i, cerebral hemispheres : m.o, medulla oblongata : o. /,
optic lobes : olf, olfactory lobes ; p.s.c, posterior semicircular canal : th,
thalamencephalon : v, vestibule : v.%, third ventricle : £-.4, fourth
ventricle : I — X, cerebral nerves.

90. The olfactory nerves (Fig. 9, I), passing directly forwards
f rozn the rhinencephala to the nasal sac, through the apertures in the
nasal capsule (§ 6).

91. 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, III), springing from

THE LAMPREY. 25

the tinier side of the mesencephalon, and passing outward; 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
S3venth nerves (Fig. 9, V, VII), leaving the brain just in front of
the auditory capsuh, and passing forwards and outwards.

95. The auditory sac (Fig. 9, r), exposed by the
removal of the dorsal wall of the auditory capsule ; it con-
sists of an ovoidal membranous sac, the vestibule (r-),
presenting on its upper surface, towards the outer side, two
semicircular canals (a.s.c, p.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 posted jr 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 caecum (Fig. 4, na'), 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 to

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 3 mm. thick in P. fluviatilis, 8 to
10 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

1 It is important not to omit this section unless time or material fails,
as it forms an excellent introduction to the art of interpreting sections.

THE SKATE.

THE SKATE (Raja bails).
THE THORNBACK (R, davata).
THE HOMELYN RAY (R. maculatd).^

A.— THE SKELETON.

I. THE 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 laminae 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, §§ 54 and 60. Several of the figures are
taken from the common New Zealand species, R. nasuta.

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, § I. 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) ; />, 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 ) > c-> shoulder-girdle and pectoral fins (§§ 42 — 49) :
</, hip-girdle and pelvic fins (§§ 50 — 53).

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
vertebne, 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 vertebrae, 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 vertebrae, extending from the posterior end of the
vertebral plate to the root of the tail, and the caudal
vertebrae, reaching to the end of that appendage.

IV. Examine the trunk vertebrae ; 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 vertebrae (Figs, n, 12, and 13, c),
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

ZOOTOMV.

l^

FIG. 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. In the remaining pectoral fin, only the proximal
ends of most of the fin rays are shown, and the cartilaginous branchial
rays are omitted for clearness sake.

ac, I, ac. 2, anterior and posterior acetabular facets : ant, antorbital
cartilage : au, auditory capsule : a.v.p, anterior vertebral plate : c.br. 3,
c.br. 5, third and fifth cerato-branchials : c.ft coracoid fontanelle : tr,

THE SKATE. 31

coracoid : cjiy, ceratohyal : e.br. 3, third epi-branchial : e.Jiy, epi-hyal :
gl. I, gl. 2, gl. 3, anterior, middle, and posterior glenoid facets :
li.br. I, h.br. 3, Ji.br. 5, hypo-branchials of the fir^t, third, and
fifth branchial arches : h.hy, hypo-hyal : Jim, hyomandibular : ha-,
commencement of haemal canal : /'/, iliac process : lb. i, lb. 2, lb. 3,
lb. 4, labial cartilages : nick, Meckel's cartilage or lower jaw : ms.pt,
mesopterygium. : mt.pt, metapterygium : ol, olfactory capsule : /./',
propterygium : p.pii, pre- pubic process : pt.qn, ptery go-quadrate
cartilage, or upper jaw : pu, pubic portion of hip girdle : >-, rostrum :
r.c, rostral cartilage : sc, scapula : s.c.f, scapulo-coraccid fontanelle :
sp, spiracular cartilage : s.sc, supra-sea pula.

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

Tt*

TLS

tr

FIG. ii. — Raja nasuta. The last seven trunk vertebrae, and the
first ten caudal vertebrce, viewed from the left side (nat. ?ize).

ct centra : cd. I, fir.-t caudal verrebra : d.r, dorsal root of spinal
nerve : h.p, hcemal process : /i.s, haemal spine : /.«, inter-neural plate :
n.p, neural process : n.s, neural spine : r, rib : /, trunk of spinal
nerve : tr, transverse process : tr. 28, twenty-eighth (last) trunk
vertebra : v.r, 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, n 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, n and 12, r\ small
pieces of cartilage attached to the ends of the transverse
processes.

FIG. 12. — Raja nasuta. A trunk vertebra, seen from the front
(nat. size).

c, centrum : i. n, inter-neural plate : n.p, neural process : n.s, neural
spine : r, rib : tr, transverse process.

8. The neural processes ('Figs, n, 12, and 13, n.p),
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.
n, v.r).

9. The neural spines (Figs, n, 12, and 13, n.s\ 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.

10. The interneural (or intercrural) plates (Figs.
ii, 12, and 13, /.«), 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. n,
d.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 vertebrae,
and containing the remains of the embryonic notochord.

V. Examine the caudal vertebrae in the same way :
make out the following points : —

12. The centrum of each vertebra (Figs, u and 14, c)
gives off, on each side, a downwardly-directed haemal
process (h.p\ which is seen, by examining the transition
region between trunk and tail (Fig. n), to be homologous
with the transverse process of a trunk vertebra : the haemal
processes, uniting below, form the haemal arch, which

J» * '•'./•. •-•
,w • • •'-•••,L£

FIG. 13. — Raja nasuta. Longitudinal vertical section cf a trunk
vertebra (nat. size).

c, centrum: i.n. , inter-neural plate: ;/./, neural process: n.s,
neural spine,

transmits the caudal artery and vein (§§ 157 and 158): a
median process, the haemal spine (/i.s), is given off at
the junction of the haemal processes of most of the
vertebrae, or may occur as a distinct cartilage (see Fig. n).

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 vertebrae : 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.

1 6. The skeleton of the caudal fin is rudimentary, con-
sisting of a few very small radial cartilages attached to the
posterior caudal vertebrae : 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).

I'"IG. 14. — Raja nasuta. A caudal vertebra, seen from the front
(nat. size).

c, centrum, h.p, haemal process : h.s, hsemal spine : n.p, neural
process : n.s, neural spine.

1 8. 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. 10, aii), 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, ol\ 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, r\ at the
sides of which the two thin rostral cartilages (r.c) are
attached.

24. In the postero-inferior region of the auditory capsule

I

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
somewhat 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

D 2

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).

VII. In the remaining loosely-attached portions of the
skull make out

34. The labial cartilages (Fig. 10, lb. i — 4), of which

THE SKATE.

37

there are altogether four, in connection with the ventral
region of each olfactory capsule : the first (Ib. i) supports
the corresponding flap of the fronto-nasal process (§ 64), the
second (Ib. 2) lies in the fold of skin external to the naso-
buccal groove (§ 64), the third (Ib. 3) bounds the nostril
internally, and the fourth (Ib. 4) externally.

35. The antorbital (palatine) cartilage (Fig. 10,
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, //.;;/), 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.
id, sp\ 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, pt.qu\ 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, mck),
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.

40. The hyoid arch (Fig. 10, e.hy, c.hy, h.hy\ a slender
rod of cartilage, attached dorsally to the postero-superior

3S 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.hy) above, cerato-hyal (c.hy] next, and
hypo-hyal (h.hy] below.

41. The five branchial arches (Fig. io),each of which
consists primarily of four segments, which are, counting from
above downwards, pharyngo-branchial, epi-branchial
(e.br], cerato-branchial (c.br\ and hypo-branchial
(h.br}. 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 (Ji.br. i) 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 (Ji.br. 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. 10).

43. The three convex articular surfaces or glenoid
facets (Fig. 10, gl. i — 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 (sct s.sc),

-that on the ventral side the coracoid region (cr).

44. The three large apertures or fontanelles which
perforate the shoulder girdle : the anterior of these is
the scapulo-coracoid fontanelle (Fig. 10, s.c.f) : 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 (c.f).

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. 10, /.//), along 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-pterygium (Fig. 10, ms.pt), 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, mt.pt), 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, pit) which sends off on each side a forwardly
directed pre-pubic process (p.pu) from the external

4o ZOOTOMV.

extremity of its anterior edge, and an iliac process (i/)
directed upwards and backwards from the external extremity
of its dorsal surface.

51. The acetabular facets (Fig. 10, ac. i, 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 calcined 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
rhomboid 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. 41

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 er\d 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.

6 1. 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 fimbriae. 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.1

1 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, a.p), 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 (pit)

—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.

' 70. 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.

75. 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, d), 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, /) (in the male) or of the ovaries (Fig. 19, oz>) and
oviducts (pd) (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, k) 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

8 1. 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 (r), from which is given off anteriorly,
and somewhat to the right side, the fleshy tubular conus
arteriosus (c.a) ; and to the dorsal side of these (beneath
in this position) the large thin-walled sub-triangular auricle
(«//), and posterior to this, the transverse, tubular, transparent
sinus venosus (s.v).

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, i.e. 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,1 first noting

85. The dura mater, or membrane lining the cerebro-
spinal cavity, in which the brain and spinal cord lie.

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. For a
permanent preparation, the brain should be placed for 24 hours in a
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 in situ, may then
be prepared by the glycerine jelly process (p. 2, § i).

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 oesophagus 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.

90. 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.

91. The fold of peritoneum — gastro-hepatic omen-
turn — 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 l 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, c.b.d} 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 v\ ith air by means
of an anatomical blowpipe. I find the following the most convenient
method for injection. Have ready four of the movable cannulas usually
provided with injecting syringes, or if these are not at hand, four glai:s
tubes drawn cut to the form shown in the annexed cut : the end a is
for insertion in the vessel, the constriction b for the

7

purpose of preventing any slipping of the ligature,
over the end c 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 (i.e.
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 cannulx 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 -e; cape. 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 arteiy, 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, /)
between them.

Running parallel with these vessels is also a transparent thin-walled
lymphatic vessel, from which many of the chief lymphatics can be
injected.

94. The gall bladder (Fig. 15, g.b\ a greenish or
yellowish transparent sac, partly imbedded in the liver
between its right and middle lobes.

r.Ld

l.fud

FIG. 15.— Raja nasuta. The gall bladder and bile ducts (half nat.
size).

c.b.d, common bile duct: c.d, cystic duct : g.b, gallbladder: l.h.d,
left hepatic duct : r.h.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-haemorrhoidal veins also often
escape being filled. In a 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

So ZOOTOMY.

95. Its passage anteriorly into the gall bladder, by the
short cystic duct (Fig. 15, c.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,
l.h.d) from the middle and left lobes, the other (r.h.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 (c.d) is very short.

XVITI. 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, /), passing towards the
middle lobe of the liver, and sending off branches to all
three lobes.

It is constituted distally by a gastric vein (Q), \\hich receives the
blocd from the stomach, and by a mesenteric vein (dti, spl, /;?, /),
\\ hich receives the blood from the intestine, spleen, and pancreas.

100. The cceliac artery (Fig. 20, CCK\ entering the
abdominal cavity on the dorsal side of the oesophagus and
dividing into two trunks, one of which, the gastro-hepatic
artery, sends off a hepatic artery (//) 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

101. 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 rupplies the intestine
(/), the other the pancreas (/;/) and spleen (<r//). The rectum is
mainly supplied by the small inferior mesenteric artery (§ 157, Fig.
20, ?.;;;•), which passes directly from the aorta to the rectal gland.

FIG. 16. — Raja nasuta. The portal vein (one-third nat. >i?e).
dit, duodenal vein : g, gastric vein : i, intestinal vein : f>, main trunk
of portal vein : pn, pancreatic veins : .<•//, splenic vein.

102. 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, //.j), a large transverse
vessel, lying across the ventral surface of the oesophagus,
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,
in the female, or the rudimentary pronephric ducts

E 2

5? ZOOTOMY.

in the male (Fig. 18, pn.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 oeso-
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 a o-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. The irregularly longitudinal ridges or rugae of the stomach.

1 08. 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 a 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, fd.s), formed by the union in the
middle line of the two posterior cardinal veins (cd), by which the bloQ

C<L>

FIG. 17. — Raja nasuta. The venous system, ventral aspect (one-
third nat. size).

The portal vein is not shown ; the renal portal vein (r.p) is supposed
to be removed on the right side (left in the figure), and the femoral
(//«), ilio-haemorrhoidal (il.h), &c., veins as well as part of the car-
dinal (cd) on the left. The right precaval sinus (pc.s) is cut open,
so as to show the apertures in its walls. The outlines of those portions
of the auricle (ait) and sinus venosus (s.v) which lie behind (dorsal
to) the ventricle (v), are dotted.

ab, veins from abdominal walls : au, auricle : b.a, bulbus anteriosus :
6r, brachial vein : c, caudal vein : c.a, conus arteriosus : cd, cardinal
vein : cd.' , posterior anastomosis of cardinal veins : cd.s, cardinal sinus :
ePg* epigastric vein : />;/, femoral vein : h.s, hepatic sinus : hce, hasmor-
rhoidal veins : HJi, ilio-haemorrhoidal vein : j.ju, inferior jugular
vein : ju, jugular vein : ly, opening of lymphatic trunk into precaval
sinus : pc.s, precaval sinus : r.p, renal portal vein : r.p', factors of
renal portal vein from pelvic and lumbar regions : r.p", branches of
renal portal veins entering kidney : sp.s, spermatic sinus : s.v, sinus
venosus : v, ventricle.

54 ZOOTOMY.

is brought back from the tail, kidneys, genital organs, 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 (pc.s) : they are
best seen at a future stage.

XXIII. The following organs are also best observed at
this stage : —

no. 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.

in. In the female the ovaries (Fig. 19, on) i these in
the young condition are indistinguishable from testes, but in
the adult state are 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, /£), flat, reddish

THE SKATE.

55

TIG. 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 oesophagus (a~s), and viewed from the ventral aspect :
the right testis (/) is removed, along with the corresponding epididymis
(epd) and all bu^ the posterior extremity of the vas deferens (v.d),
which, with the sperm sac (s.s) is turned outwards to display the
ureters (ter) : the cloaca (<:/), the urinogenital sinus (ug.s), and the
right vesicula seminalis (v.s) and sperm sac (s.s) are laid open.

a.p, abdominal pore : ct, cloaca : epd, epididymis : i.r, inter-renal
body : k, kidney : as, oesophagus : pn.d, pronephric duct : s.s, sperm
sac : s.s', its opening into the urinogenital sinus : /, testis : Hg.p, urino-
ge.iital papilla: ug.s, urinogenital sinus: ^lr, ureter: ur1, its opening
into the urinogenital sinus: v.d, vas deferens : v.st vesicula seminalis :
v.s', its opening into the sperm sac.

56 ZOOTOMY.

brown, tabulated bodies, lying close to the dorsal wall of
the abdominal cavity, and covered, on their ventral surfaces
only, by peritoneum.

/;/ the male.

114. The epididymes (Fig. 18, epd), 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.d\ 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 be
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. 1 8, pn.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).

In the female.

118. The oviducts (Fig. 19, fl. /,///), each of which
consists of two parts : a posterior, wide, thick-walled uterine

THE SKATE.

57

portion (///), opening into the cloaca, and an anterior,
slender, thin-walled portion, or Fallopian tube (/?./)
which unites with its fellow of the opposite side on the

ur

FIG. 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 oesophagus (as), 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.

a.p, abdominal pore: cl, cloaca: fl.t, Fallopian tube, or anterior
portion of oviduct : fl.f, common opening of the conjoined Fallopian
tubes into the abdominal cavity : k, kidney : mn.d, mesonephric duct :
od.g, oviducal gland : ces, oesophagus : ov, ovary : ti.b, urinary bladder :
u.p, urinary papilla : zir, ureters : ut, uterine portion of oviduct :
ut'y its opening into the cloaca.

58 ZOOTOMY.

I

ventral surface of the gullet, where the two tubes have a
common oval opening (fl.t') 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.

119. The urinary bladder (Fig. 19, u.b) 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).

XXV. Open the cloaca by a median incision along its
ventral wall, and note in it

1 20. The opening of the rectum.
In ike male.

121. A small, thin-walled tube, the urinogenital papilla
(Fig. 1 8, iig.p), 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, ?//'), 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, ii.p\ 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.

/;/ the male.1
XXVI. 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 SKAfE. 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, ug.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 (//;-') 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. 1 8, 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 defereus and note

127. Its expansion posteriorly into a chamber — a sort of vesicula
seminalis (Fig. 18, v.s), which has its walls produced into lamince,
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, ur\ 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 slit-like aperture
already noticed.

129. The inter-renal (Fig. 18, *>), 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 ganglia.

130. The cardinal veins (Fig. 17, flying to the ventral side of
the ureters, receiving veins from the kidney?, 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.ao), 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.

In 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 w\ 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, mn.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 note

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-

In 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, b.ci), a white dilatation, connected with the anterior
end of the conus arteriosus or pylangium (c.a, § 82), and
giving off three vessels, one anteriorly, the ventral aorta
(v.ao], and one on each side, the posterior innominate
arteries (p-in\ The ventral aorta passes forwards to the
level of the anterior gill cavity, and there divides into two
vessels, the anterior innominate arteries (a.tn) 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. i — 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 hypobranchiai artery (Figs. 20 and 21, hy.lr], 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 of the gills, sends off an anterior coronary artery (Figs. 20 and
21, a.cd] to the conus arteriosus and ventricle, and a posterior
coronary (p.co), to the sinus venosus.

62

ZOOTOMV.

ek./

FIG. 20. — Raja nasuta. The arterial system, seen from the ventral
aspect (one-third nat. size).

The heart and ventral ao^a (v.ao) are slightly displaced towards the
right side (left in the figure) : the left afferent branchial arteries (a.h)
are removed, and the right efferent branchials (e.br) : the lett efferent
branchials are straightened out, so as to bring their ventral ends to the

THE SKATE.

extreme right of the figure: the left hypobranchinl artery is also
displaced outwards ; that of the right side (left in the figure) (hy.br]
is drawn in situ.

a,br. I, first, and a.br. 5, last afferent branchial artery : a.co, anterior
coronary artery : a.in, anterior innominate artery : b.a, bulbus arterio-
sus : br, brachial artery : c, caudal artery : c.a, conus arteriosus :
c.c, common carotid art 617 : ccs, coeliac artery : d, duodenal artery :
d.ao, dorsal aorta : e.br. I, first, and e.br. 9, last efferent branchial
artery : e.c, external carotid artery : f.n, artery to fronto-nasal process :
.<?"> gastric artery: //, hepatic artery: hy, hyoidean artery: hy.br,
hypobranchial artery: /, intestinal artery: i.c, internal carotid artery:
//, iliac artery : i.m, inferior mesenteric artery : nin, artery to man-
dible : n.br, nutrient arteries of the gills : od, oviducal arteries : p.co,
posterior coronary artery : p.in, posterior innominate artery : pn,
pancreatic arteries : r, renal arteries : s, artery to snout : s.cl, sub-
clavian artery: s.m, superior mesenteric artery: spl, splenic artery:
spm, spermatic artery : v, ventricle : v.ao, ventral aorta : z>r, vertebral
artery.

140. The inferior jugular vein (Figs. 17 and 21, i.jn) 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 dnus (§ 149, Figs. 17 and 21, pc.s).

J.ao

br.v

n.lr

FIG. 21. — Raja nasuta. Diagram of the heart ar.d chief blood-
vessel-, from the left side (half nat. size).

a.br. I, first, and a.br. 5, last afferent branchial artery : a.co, anterior
coronary artery: au, auricle: br.a, brachial or subclavian artery:
br.v, brachial vein : c.a, conus arteriosus : cd, cardinal vein : d.ao,
dorsal aorta : e.br. I, first, and e.br. 9, last efferent branchial artery :
h.s, hepatic sinus : hy, hyoidean artery : hy.br, hypo-branchial artery :
i.ju, inferior jugular vein : ju, jugular vein: n.br, nutrient arteries cf
the gills: p.co, posterior coronary artery: pc.s, precaval sinus: s.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.
These — 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
tioth 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 columnse carnese.

148. The three longitudinal rows of aortic valves in

THE SKATE. 65

the conus arteriosus, each row containing five somewhat
semilimar 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 2i,pc.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 (;«), by which the blood is returned from the
head : another, postero-internal in position, is fhe 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 (/i.s) : a fourth,
at its anterior end, kads into the sinus venosus (s.v) : a fifth, very
small, just internal to the last, into the inferior jugular vein (i.ju} : a
sixth, on the outer wall, into the brachial vein (fir) 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,
ly] are 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 oesophagus
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

151. 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 is the 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.

XXXVIII. 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, e.br. i — 9), 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 take a 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 \\ ell as at their dorsal ends, thus forming
complete loop?, 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.br. 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, d.ad), 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.cl, Fig. 21, br.a). 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 cceliac (Fig. 20, cat), and
superior mesenteric (s.m) arteries (§§ 100 and 101),
then the arteries to the oviducts (od) or epididymes, sper-
matic arteries (spm) to the testes or ovaries, a single
inferior mesenteric artery (/.;;/), (§ 101), the numer-
ous small renal arteries (r) 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 haemal arches of the
caudal vertebrae (Fig. 10, /ice) to the end of the tail.

158. The caudal vein (Fig. 17, c), running parallel and ventral
to the caudal artery : on leaving the haemal canal it divides into the two
renal portal veins (rp\ which pass to and ramify in the corre-
sponding kidneys (r/1) receiving numerous veins (rp1) 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, theiiio-hsemorrhoidal
vein (ilJi), 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
(fpg) ; it passes almost directly forward along the lateral wall of the
abdominal cavity, receiving veins from the abdominal walls (a£), and
finally unites with the brachial vein (br).

It will be seen from Fig. 17, that the brachial, epigastric and ilio-
hseinorrhoidal 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.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 (i.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 (e.c) then passes
forwards and slightly outwards, and sends branches to the jaws,
snout, &c.

161. The vertebral artery (Fig. 20, vr)i 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, hy) 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. If a 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, c.r\ Both dorsal and
ventral surfaces of the medulla are marked with obscure
median 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, ?'. 4), roofing over the fourth ventricle (§ 180).

173. The mesencephalon (Figs. 22 — 25, <?./, c.c) con-
sisting on the upper surface of the two optic lobes
(<?./), 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

THE SKATE.

FIG. 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 — roth 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 : m.o, medulla
oblongata : v. 4, fourth ventricle : c.r, corpora restiformia : cb, cere-
bellum : oj, optic lobes: th, thalamencephalon : c.h, prosencephalon :
olfi olfactory lobes.

Nerves. /, olfactory: II, optic: ///, oculomotor: i.r, branch of
oculomotor to internal rectus : s.r, to superior rectus : it.r, to in-
ferior rectus : i.o, to inferior oblique : IV, patheticus : FIa, dorsal,

72 ZOOTOMY.

and Flb, ventral ramus of F1 orbito-nasal nenre : F2a, palato-nasal
nerve : F2b, maxillary nerve : F3, mandibular nerve : F//a, palatine
branch of portio dura: F//b, hyomandibular branch: c.ly, chorda
tympani : VIII, auditory nerve : IX, glossopharyngeal nerve : X, vagus :
hy, branch of glossopharyngeal to hyoid arch : br. I, branches of
glossopharyngeal and vagus to 1st branchial arch: br. 2, br. 3, br. 4,
branches of vagus to 2nd, 3rd, and 4th branchial arches : v, ventral
(gastric and cardiac) branch of vagus : /, lateral branch of vagus : br,
brachial plexus.

forward continuations of the ventral pyramids of the
medulla oblongata.

174. The thalamencephalon (Figs. 22, 24, 25, th\ 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 thalamocceie or third ventricle (v. 3).

175. The lobi inferiores (Figs. 23 — 25, /./) paired
ovoidal bodies on the under surface of the thalamencephalon.

176. The pituitary body or hypophysis cerebri
(Figs. 23 — 25, //), 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, s.z>, s.i>).
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.

178. The prosencephalon (Figs. 22 — 25, c.h\ a large
transversely elongated mass, in front of the thalamen-
cephalon and representing the fused cerebral hemispheres.

179. The olfactory lobes (Figs. 22 — 25, 7), two long,
nerve-like bodies, given off from the antero-lateral angles

THE SKATE. 73

of the prosencephalon, and passing forwards and slightly
outwards to the olfactory foramina (§32). Their further
course will be seen at a later stage (§ 206).

1 80. By lifting up or removing the cerebellum, the
whole extent of the fourth ventricle or myeloccele
(Figs. 22 and 24, v. 4) is seen : viewed from above it has a
triangular shape, the base being forwards, and the apex
(calamus scriptorius) backwards, as already seen.

/ -, ••,.., '
vnr

FIG. 23. — Raja batis. The brain from beneath (half nat. size).

Only the proximal portions of the olfactory lobes are shown.

m.o, medulla oblongata : pt, pituitary body : s.v, saccus vasculosus :
/.% lobi inferiores : i.c, internal carotid artery : o.f, optic chiasma : c.k,
prosencephalon : I—X, cerebral nerves.

1 8 1. By carefully cutting away the optic lobes, the fourth
ventricle is seen to be continuous with a cavity in the
mesencephalon, the aqueduct of Sylvius or mesocoele
(Fig. 24, aq. s), which sends lateral prolongations into the
optic lobes. Anteriorly the mesoccele is seen to be con-
tinuous with the thalamoccele (r. 3).

182. By cutting into the prosencephalon, it is seen to be
solid, lateral ventricles (prosocceles) being absent.

183. From the under surface of the thalamencephalon
arise the two large optic (second cerebral) nerves (Figs. 22,

74

ZOOTOMY.

23, and 25, 77) : their proximal ends are fused together to
form an optic chiasma (Fig. 23, o.c). Each nerve
passes outwards and forwards to the corresponding optic
foramen (§ 30).

.4

FIG. 24. — Raja batis. Longitudinal vertical section of the brain

(half nat. size).

m.o, medulla oblongata : z>. 4, fourth ventricle : cb, cerebellum :
c.c, cms cerebri : o.l, optic lobe: aq.s, aqueduct of Sylvius: ///,
thalamencephalon : v. 3, third ventricle: l.i, lobus inferior: c./i,
prosencephalon.

184. The third pair of nerves (oculomotores, Figs 22,
23, 25, 777), arising one on either side of the base of the
brain from the crura cerebri, a little behind the lobi infe-
riores, and passing outwards and forwards to their foramina
in the side walls of the skull (§ 30).

civ

E m.0

FIG. 25. — Raja batis. Side view of the brain (half nat. size).

m.f>, medulla oblongata : cb, cerebellum: i.c, internal carotid artery:
o.l, optic lobe://, pituitary body: s v, s.v', saccns vasculosus : th,
thalamencephalon: c./i, prosencephalon: I—X, cerebral nerves.

185. The fourth pair of nerves (pathetici, Figs. 22, 23,
25, IV), delicate threads which proceed from beneath the
antero-lateral regions of the cerebellum, outwards and
fonvards to their foramina in the side walls of the skull

(* 30).

THE SKATE. 75

1 86. T\vo large bundles of nerves proceeding one from
either side of the medulla oblongata, beneath the restiform

FIG. 26. — Raja nasuta. External view of the roots of the 5th, yth,
and 8th cerebral nerves of the left side (nat. size).

Va. Fa/, ventral or anterior roots of the trigeminal : Fb, dorsal or
posterior root of the same : VII, VII', roots of the portio dura : VIII,
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'A] goes to form the inferior ramus of the

VDT

FIG. 27. — Raja nasuta. The principal branches of the 5th, 7th, and
8th cerebral nerves (nat. size).

Fa, ventral and Fb, dorsal root of the fifth: FIa, dorsal, and F'b,
ventral ramus of the orbito-nasal nerve : F2a, palato-nasal nerve : _F2b,
maxillary nerve : F3, mandibular nerve : pt.qu, nerve to upper jaw^.
na, nerves to the region of the nostrils : VII, portio dura : VIII,
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 (Fb, VII, VIII) 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, Va') and a larger ventral ( Fa)
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 a posterior set. The anterior
set consists of two roots, a dorsal ( VII} and a ventral ( VII'), together
forming the seventh nerve : the posterior set consists of three roots, a
dorsal (Vb), 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 (Vb) : the lowermost ventral root (VIII) constitutes the eighth
nerve.

187. The sixth pair (abducentes. Figs. 22 and 23, VI)
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, IX), 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, Fia) 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, IV), 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, 7/7), which, after leav-
ing the skull, sends branches to the superior (s.r) and
internal (i.r) 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, VI\ 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, Flb) 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, //), 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,
///): after curving round the superior rectus, it passes
forwards and sends branches to the inferior rectus (it.r) and
inferior oblique (i.o).

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, V1) 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, o/f\
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 right
angles to a central ridge.

XLV. Remove the eye with its remaining muscles, and
set it aside for future examination.1 Dissect out

209. The second division of the fifth nerve (Figs. 22 and 27,
F2), arising mainly from the posterior fasciculus mentioned
in § 1 86, 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 (F2a) and an external, the maxillary nerve ( F2b)
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

(S 35).

210. The third division of the fifth, or mandibular

nerve (V3), 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 nostrils ; it also sends

1 The eye must be dissected in the fresh condition : for directions see
§ LI I., p. 84.

So 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, Vli rb): 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 (c.ty), 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, 7/77*), 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 (7;),
and three semicircular canals, one of which is anterior
and vertical (a.s.c\ another posterior and vertical (p.s.c), and
the third horizontal (h.s.c).

THE SKATE. Si

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 (aq.f), 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 by a 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).

^ a.s.O

}v.s.c-

FiG. 28. — Raja batis. The right membranous labyrinth, seen from
the outer side (nat. size).

v, vestibule : aq.f, aqueductus vestibuli : a.s.c, anterior, p.s.c,
posterior, and h.s.c, horizontal semicircular canals : a, a, a, ampullae :
X, side tubulure by which the posterior canal communicates with the
vestibule : n,n,n, 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,v), to the stomach and heart, and a lateral branch
,f), which passes between the peritoneum and dorsal

G

8- ZOOTOMY.

muscles, on the dorsal side of the spinal nerves (§ 222).
The branchial nerves (br. 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.

215. The glossopharyngeal or ninth nerve (Fig. 22,
fX), 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 (hy, br.i).

216. The brachial plexus (Fig. 22, br), 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. n, d.r) and a
ventral (v.r), 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 (/;-) 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, VIII),
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 ampullae of the semicircular
canals (Fig. 28, n).

218. The course of the ninth nerve through the capsule
(Fig. 22, IX) : 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, -AT): 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,l), a longitudinal nerve, lying to the dorsal side cf 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

G 2

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 (aq.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).

225. 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 (i.e. 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.

THE CODFISH (Gadus morrhua).
THE WHITING (G. merlangus).
THE HADDOCK (G. (zglefinus).1

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, pa) and the hyomandibular (§ 40,
Fig. 29, hm). 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 : —

i. The vertebral column, consisting of (a) trunk
vertebrae, 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 (parietal^
f rentals, 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 (b) caudal vertebrae, with complete inferior
arches.

2. The skull, consisting of (a) the brain-case, formed
of a number of bones firmly united by suture ; (b) 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 (c) 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 outside 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 : —

9. 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
vertebrae, and in consequence the atlas is, in preparation,
often left attached to the skull.

10. In the next three or four vertebras 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

9o 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 vertebrae note ,

15. The haemal arch, formed by the union in the
middle ventral line of two haemal processes, springing one
from each side of the ventral surface of the centrum near
its anterior end ; from the point of union a haemal spine is
given off and passes downwards and backwards. The
haemal 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.

1 6. In the anterior caudal region the haemal 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 haemal aspects of the
vertebras.

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

TS. The interspinous bones of the dorsal and anal
fins, alternating with the neural and haemal spines respec-
tively, and attached to them by fibrous tissue.

THE COD. 91

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
vertebrce 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 haemal spines.

In the Codfish there are 13 rays to the first dorsal fin, 1 6 to 19 to
the second, 17 — 19 to the third, 18 — 19 to the first anal, and 17 — 18 to
the second. The formula for the fin rays is therefore, U. 13 [ 16 — 19 |
17 — 19. A. 18 — 19 | 17 — 19. In the Haddock the formula is D.
14 — 16 | 20 — 24 | 19 — 21. A. 24 — 25 | 21 — 21 ; and in the Whiting
D. 13 — 14 | 20 — 23 | 20 — 21. A. 33—35 | 22 — 24.

^

VII. In the brain-case make out the following points : —

20. The single concave occipital condyle, for articu-
lation with the centrum of the atlas : it is the hinder face
of the basi-occipital bone (Fig. 29, b.o), which forms the
posterior part of the base of the skull, ending in front by a
thin jagged edge.

21. The foramen magnum or occipital foramen, a
large aperture immediately above the occipital condyle, for
the passage of the spinal cord into the brain.

22. The ex-occipitals (e.o), two irregular bones forming
the lateral boundaries of the foramen magnum and articu-
lating below with the dorso-lateral edges of the basi-occipital.
Each ex-occipital is perforated by an aperture for the exit of
the vagus nerve, and presents on its posterior border an arti-
cular facet for the corresponding surface already seen on the
neural arch of the atlas (§ 9).

23. The supra-occipital (s.o), a large bone bounding

ZOOTOMY.

na

m.e

cp.o

op

v.Jty

br.r

s.op

FIG. 29.— Gadus morrhua. The bones of the skull, disarticulated
and viewed from the left side (| nat. size).

0/.J, alisphenoid : an, angular : ar, articular : b.o, basioccipital
br.r, _ branchiostegal rays : c.hy, cerato-hyal : d, dentary : e.o, ex-
occipital : ep.hy, epihyal : ep.o, epiotic : fr. frontal : h.hy, hypohyal :
hm, hyomandibular : i.hy, interhyal : i.op, inter-opercular : Ic, lachry-
mal : m.e, mesethmoid : m.pt, metapterygoid : ms.pt, mesopterygoid •
mx, maxilla : na, nasal : op, opercular : cp.o, opisthotic : /, parietal •
pa.s, parasphenoid : p.e, parethmoid : pa, palatine : p.mx, prem axilla •
p.op preopercular : pr.o, prootic : pt, pterygoid : pt.o, pterotic : gu
quadrate s.o, supraoccipital : s.op, subopercular : s.or, suborbitals •
sp.o, sphenotic : sy, symplectic : u./iy, urohyal : vo, vomer : x, articular
facet on parethmoid : x', articular facet on palatine : y, articular facet
on sphenotic and pterotic : /, articular facet on hyomandibular.

THE COD. 93

the foramen magnum above, and produced dorsally into a
median, laterally-compressed crest, the occipital spine.
The basi-, ex-, and supra-occipitals together form the
occipital segment of the skull.

24. Externally to the occipital region, the brain-case is
produced on either side into a large out-standing mass, the
auditory capsule, which presents above two well-marked
processes — an inner, the epiotic process, short and sub-
tetrahedral in form ; and an outer, the parotic process,
which is long, and projects backwards and outwards. The
median occipital spine and the paired epiotic and parotic
processes form the five projections which are so marked a
feature in the postero-dorsal region of the skull.

25. The epiotic process forms nearly the whole of the
small epiotic bone (ep.o\ the postero-internal ossification
of the auditory capsule.

26. The parotic process is constituted by two bones,
which are seen to meet in an irregular suture on its outer
surface. The uppermost of these is the pterotic (pt.o),
or postero-dorsal ossification of the auditory capsule, the
lower the opisthotic (op.o), or postero-ventral ossification :
the latter articulates behind with the ex-occipital, and
below with the basi-occipital, and is perforated near its
posterior border by a foramen for the exit of the glosso-
pharyngeal nerve.

27. The pro otic (pr.o), a large bone, articulating behind
with the opisthotic and forming the antero-ventral ossifi-
cation of the auditory capsule : its anterior border is
deeply notched for the passage of the fifth and seventh
cerebral nerves.

28. The sphenotic (sp.o), the antero-dorsal ossification
of the auditory capsule, a large, irregular bone, articulating
behind with the pterotic and below with the prootic.

94 ZOOTOMY.

29. A large articular surface (}') on the side wall of
the auditory capsule, formed in front by the sphenotic,
behind by the pterotic ; it is covered with cartilage in the
recent state and gives articulation to the hyomandibular

(§ 40).

30. The frontals (/;-) united with one another in the
middle line into a single large shield-shaped bone which
forms the greater part of the roof of the brain-case, articu-
lating behind with the supra-occipital in the middle line,
and with the sphenotics externally.

31. The parietals (/>), two flat bones, completing the
roofing-in of the brain-case, being wedged in, one on either
side, between the supra-occipital internally, the sphenotic
and pterotic externally, the frontal in front and the epiotic
behind. On the dorsal surface of the parietal is a spine-like
process, beneath which is a foramen for the exit of the
cutaneous branch of the fifth nerve (§ 98).

32. The alisphenoids (al.s), two small bones, situated
in the side walls of the brain-case, and articulating with the
prootic behind and below, and the frontal and sphenotic
above.

33. The parasphenoid (pa.s\ a long, stout, median
bone, forming the greater part of the base of the skull :
posteriorly it widens out, underlaps the basi-occipital and
articulates with the prootics : both in front and behind it
thins out considerably and ends in a jagged edge.

34. The vomer (ZY?), a median bone, forming the
anterior part of the base of the skull : it ends in front in a
strong transversely curved edge, beset with teeth on its
lower surface (§ 161), posteriorly it is pointed and under-
laps the parasphenoid.

35. The mesethmoid (m.e), a median bone situated
immediately above the vomer : it is truncated in front, and

THE COD. 95

sends off backwards a long process which fits into a deep
notch in the frontals.

36. The parethmoids (p.e\ irregular paired bones
forming large lateral projections at the anterior end of the
brain-case, representing ossifications of the olfactory capsules.
Each presents on its outer surface an articular cavity (jf) for
the palatine (§ 46).

37. A vacuity on each side between the mesethmoid,
the parethmoid, and the frontal, and serving to lodge the
nasal sac (§ 180).

38. The absence of side walls to the skull except in the
olfactory and auditory regions.

39. A longitudinal section shows that in the dried skull
there is free communication between the cavity for the brain
and those for the auditory organs.

VIII. In each side of the upper jaw and suspenso-
rium make out

40. The hyomandibular (/im), a large bone articulat-
ing with the facet (y) afforded by the sphenotic and pterotic
by a prominent rounded head (y) : it sends off a long
backward process for articulation with the opercular,
and presents on its outer surface a prominent, down-
wardly directed ridge serving for muscular attachments,
and perforated anteriorly by two foramina for the seventh
nerve. At its lower end the hyomandibular ends in
front in a jagged triangular process, behind in a straight
edge.

41. The symplectic (sy), a long, somewhat triangular
bone, having a short dorsal edge united by synchondrosis
with the straight lower border of the hyomandibular, and a
pointed ventral process which fits into a groove on the inner
face of the quadrate (§ 42). In the natural position of the
bones, the symplectic, as well as a considerable portion of

96 ZOOTOMY.

the hyomandibular and quadrate, is hidden by the pre-
opercular (§ 64).

42. The quadrate (qii) a bone of very irregular form,
presenting on its inner surface a deep groove for the re-
ception of the symplectic, and ending below in a saddle-
shaped articulation for the lower jaw.

43. The meta-pterygoid (m.pt), a thin lamina of bone,
united by synchondrosis with the straight part of the dorsal
border of the quadrate, and fitting closely against the
anterior border of the hyomandibular and symplectic.

44. The pterygoid (//), a long, flat, irregular bone,
with a thickened ventral border : it articulates by suture
with the anterior edge of the quadrate and meta-pterygoid,
and takes a direction forwards, and slightly upwards and
inwards.

45. The meso-pterygoid (ms.pt\ a very thin bony
lamina, fitting against the upper edge of the pterygoid.

46. The palatine (pa), an irregular bone, consisting of
a flattened posterior portion, and of a stout, rod-like,
incurved anterior portion ; at the junction of its two
parts, the bone presents on its upper surface an articular
facet (xr) for articulation with the parethmoid (§ 36). Pos-
teriorly the palatine ends above in a straight edge, and
below in a long jagged process which articulates with
the pterygoid.

47. The premaxilla (p.mx), a stout, curved, rod-like
bone forming the gape of the upper jaw, produced at
its upper or inner end into a strong upward process, and
covered on its oral surface with close-set curved teeth.

The two premaxillas abut at their dorsal (inner) ends against a large
nodule of cartilage, which is not seen in the dried skull.

48. The maxilla (mx), lying behind and parallel with
the premaxilla : its anterior (dorsal) somewhat expanded

THE COD. 97

end articulates with the vomer : its posterior (or ventral)
flattened end reaches nearly as far back as the quadrate. It
does not enter into the gape.

IX. Note the following bones in each ramus of the lower
jaw :—

49. The articular (ar\ a large bone articulating by a
saddle-shaped surface with the quadrate : it is thick and
strong posteriorly, and produced into a long pointed pro-
cess anteriorly. On its inner surface is a groove in which,
in the recent condition, Meckel's cartilage lies : this
latter is rod-like, about 2 — 5 mm. in diameter, and pointed
at its anterior end, which projects beyond that of the
articular.

50. The angular (an\ a small stout bone attached to
the postero-inferior angle of the articular.

51. The dentary (d), a large bone forming the main
part of the lower jaw, and curving inwards to join its fellow
of the opposite side, to which it is united by synchondrosis.
Its posterior edge is deeply notched for the reception of the
articular, and it contains a cavity open behind, in which
Meckel's cartilage and the mandibular nerves run.

X. Note in the hyoidean apparatus

52. The two paired halves or cornua of the apparatus,
large, laterally-compressed bones, lying, in the natural
position of the parts, within the rami of the mandible, and
uniting with one another by a median symphysis a short
distance behind the mandibular symphysis.

53. The connection of each hyoidean cornu with the cor-
responding suspensorium by a short rod of bone, the inter-
hyal (i./iy), which articulates on the one end with the
dorsal extremity of the cornu, and on the other with the
cartilaginous interval between the hyomandibular and
symplectic.

H

98 ZOOTOMY.

54. The composition of the hyoidean cornua : each con-
sists of a dorsal, somewhat triangular bone, the epi-hyal
(ep.hy), articulating at its apex with the inter-hyal, and at
its base united by suture to a second bone, the cerato-hyal
(c.hy), which forms the main part of the cornu, and is
connected ventrally with two small ossifications, the hypo-

hyals (h.hy).

55. The branchiostegal rays (br.r), seven^ curved
rods of bone, articulated to about the upper three-fourths of
the posterior edge of the cerato-hyal : the four superior rays
are connected with the outer face, the three inferior with
the inner face of the cerato-hyal.

56. The uro-hyal or basi-branchiostegal (u.hy), a
median vertical plate of somewhat triangular form, inter-
posed between the hypo-hyals of opposite sides.

XI. In the branchial arches, make out

57. The superior pharyngeal bones, two large
irregular bones, covered inferiorly with teeth, which lie, in
the entire fish, in the roof of the pharynx. These represent
the coalesced dorsal elements or pharyngo-branchials of
the four anterior branchial arches.

58. The epi-branchials, four slender bones standing
out horizontally from the outer edge of each superior
pharyngeal bone.

59. The cerato-branchials, four larger bones on each
side, forming the main part of the four anterior branchial
arches : each is articulated at its dorsal end with the outer
(ventral) extremity of the corresponding epi-branchiai, and
takes a direction forwards, downwards, and slightly inwards.

60. Each cerato-branchial is articulated below with a
hypo-branchial ossification, which passes forwards and
inwards.

61. The basi-branchial, a median ventral ossification,

THE COD. 90

common to the first three arches, the hypo-branchials of which
articulate with it laterally : the hypo-branchials of the fourth
arch are united with one another in the middle ventral
line by cartilage.

62. The rudimentary fifth branchial arches, each consist-
ing of a single bone — the inferior pharyngeal bone

-which is beset on its dorsal face with teeth, and in
the entire fish, bites against the superior pharyngeal
(§§ 162, 163).

XII. In the skeleton of the gill-cover or operculum,
note the following four bones on each side :-

63. The opercular (Fig. 29, op), a flat bone, bifid
posteriorly and having on its anterior border a facet for
articulation with the posterior or opercular process of
the hyomandibular.

64. The pre-opercular (p.op\ a large bone with an
evenly curved anterior border produced at one place into
an irregular process, and a jagged posterior border ; its outer
face is produced into a prominent ridge for attachment of
muscles. In the natural position of the parts it fits closely
against the outer face of the hyomandibular, symplectic,
and quadrate.

65. The sub-opercular (s.op), a flat plate, somewhat
rounded below and pointed above : and lies immediately
beneath the opercular.

66. The inter-opercular (t.op), an irregular bone,
articulated at its upper and posterior end with the sub-
opercular, and at its opposite extremity connected by ligament
to the angle of the mandible.

XIII. There still remain a few loosely attached bones
in connection with the brain-case, chiefly in the
region of the nose and eyes; these are

67. The so-called nasals (na)t delicate scale-like bones,

H 2

ioo ZOOTOMY.

grooved for sensory tubes, situated one on either side of the
nasal region, to the dorsal side of the parethmoids.

68. The sub-orbitals (s.or), a semicircular chain of
bones, lying beneath the eye-ball : the most anterior of the
series is large, thin, and triangular in shape, and is the so-
called lacrymal (lc) \ the others are small and five to
seven in number. All are grooved for sensory tubes.

69. Two or three small grooved bones of a similar
nature occur in relation to the parotic processes.

XIV. In the shoulder-girdle and pectoral ^fin note on
each side

70. The post-temporal, a forked bone, articulating by
the inner and larger of its limbs with the epiotic, by the
outer and smaller with the parotic process of the skull.

71. The supra-clavicle, a stout rod, articulating above
with the post-temporal, and fitting below by its bevelled
inner surface against the dorsal extremity of the clavicle.

72. The clavicle, a large curved bone, with a thick
anterior and a thin posterior border, attached above to the
supra-clavicle, and taking a direction at first downwards,
then forwards and inwards, so as nearly to meet its fellow
of the opposite side in the middle ventral line of the throat,
a short distance beyond the uro-hyal.

In the Haddock the anterior (ventral) portion of the clavicle is greatly
thickened.

73. The post-clavicle, a slender bony rod, connected
with the inner face of the clavicle near its dorsal end, and
passing backwards and downwards.

74. The scapula and coracoid, two delicate lamina?
attached to the inner face of the clavicle : the upper and
smaller of the two is the scapula : the lower, of an irregularly
triangular form, is the coracoid.

THE COD. 1 01

75. The brachial ossicles, four small, dice-box
shaped bones, articulating with the posterior border of the
scapula and coracoid.

76. The fin-rays, attached to the distal ends of the
brachial ossicles and having essentially the same character
as those of the median fins ; they diminish gradually in size
from the pre-axial to the post-axial border of the fin (see
§ 95) overlap one another at their proximal ends, and are
much frayed out at their distal extremities.

XV. In the hip-girdle and pelvic fins note

77. The pelvis, consisting of the two thin, irregular
innominate bones,1 united with one another in the middle
ventral line, but showing no distinction into the three
ossifications of the typical vertebrate os innominatum.

78. The fin-rays, articulating with the postero-external
"borders of the innominate bones. Owing to the position
of the pelvic girdle beneath the throat, the pelvic fins come
to be situated anterior to the pectorals.

B.— DIRECTIONS FOR DISSECTION.

XVI. Make out the following external characters :-

79. The elongated body (Fig. 30), slightly compressed
from side to side ; the head passing insensibly into the
trunk, and the trunk into the tail.

80. The integument, containing numerous small
imbricating scales, covered with a layer of thin, slimy,
pigmented epiderm, the colour of which varies in differ-
ent parts of the body, being white below, and greyish or
olive, mottled with golden yellow, above.

It is possible that the so-called innominate bone may represent the
basale metapterygii or basipterygium of the Elasmobranch fin (p. 40,
§ 52), and not a true pelvic girdle.

102 ZOOTOMY.

In the Haddock the lateral line (see § 82), is black, and there is also
a blackish blotch below the lateral line, between the pectoral and the
first dorsal fins : in the Whiting there is a black spot on the axil of
the pectoral fin.

8 1. Remove a few scales and examine under a low
magnifying power ; each is seen to be a flat, rounded plate,
composed of concentric laminae of calcific matter, devoid
of bone-cells ; its anterior end is embedded in the derm
and overlapped by other scales, its posterior end is covered
only by epiderm, and presents an even free border ("cycloid "
scales).

82. The lateral line,, a horizontal row of peculiarly
modified scales, lodging sensory tubes ; it passes from the
tail forwards, a little above the middle line of the body, and
becomes indistinct on the head.

83. The large mouth, at the extreme anterior end of
the body, supported below by the mandible (Fig. 29, d) and
above by the premaxillcc (p.mx) and maxillae (inx\ of
which the latter are behind the former and do not actually
enter into the gape. The skin in which the maxilla and pre-
maxilla are contained is so loose as to render the upper jaw
slightly protrusible.

84. The teeth are best seen at a later stage (§§ 159-
163, p. 120).

85. The barbule (Fig. 30, £), a median filamentous
process, hanging from the under side of the lower jaw near
the symphysis.

In the Cod the barbule is a^ long as or longer than the eye : in the
Haddock it is very short : in the Whiting absent.

86. The nostrils (anterior nares) (Fig. 30, n.a), situated
a short distance behind the blunt anterior extremity of the
snout ; these are two small apertures on each side, of which

THE COD. 103

the posterior and outer is circular and open, while the
anterior and inner is guarded by a flap-like valve.

87. The large eyes (<?), devoid of eyelids and covered
with a continuous layer of transparent integument.

88. The gill-opening, a large crescentic aperture on
each side, extending from under the throat upwards and
backwards along the side of the head ; it is bounded be-
hind by the shoulder-girdle (§ 95) and in front by the gill-
cover or operculum, which is easily distinguishable into two
part?, the operculum proper (Fig. 30, op\ supported by
the opercular bones (§§ 63 — -66), and the branchiostegal
membrane (br.m}, supported by the branchiostegal rays
of the hyoid bone (§ 55).

89. The gills, seen by lifting up the operculum: they
are four in number, and consist of rows of deep red
branchial filaments, supported on the four anterior
branchial arches (§§ 57 — 62) ; between the gills, as well as
in front of the first and behind the last gill, are the bran-
chial clefts, five in number, leading into the cavity of
the mouth.

90. The pseudobranchia (rudimentary hyoidean gill),
seen as a red patch covered by semi-transparent mucous
membrane, on the inner surface of the gill-cover, a little
anterior to the dorsal end of the first branchial arch.

91. The absence of spiracles (p. 43, § 70) and of external
auditory apertures.

92. The anus (Fig. 30,0), a somewhat prominent aperture,
situated in the middle ventral line, about half-way between
the snout and the end of the tail.

93. The genital (g) and urinary (;/) apertures,
situated on a common elevation of integument, immediately
posterior to the anus ; they are small apertures, the genital
being the more anterior of the two.

104

ZOOTOMV.

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a; cj p

^ t t °

v C ii

C C 5

8

c

0 S 5

c o; O

- c

.'S § J2 . C "o

o t 9 c

IT; rf ^
S *-< o

_c
"o

cx

•S r*

o M"

THE COD. 105

94. The median fins, thin vertical folds of integument
supported by bony fin-rays (§ 19) ; three of them are dorsal
in position (dorsal fins, Fig. 30, d.f. i, d.f. 2, d.f. 3), ex-
tending from immediately behind the head to the tail ; two
are ventral (anal fins, a.f. i, a.f. 2), extending between
the urinary aperture and the tail ; and one is posterior, the
caudal fin (c.f] ; the latter is apparently quite symmetrical
(homocercal), its rays being equally distributed above and
below the fleshy lobe in which the tail ends.

95. The pectoral fins (fore-limbs) (Fig. 2,/./), situated
on each side of the anterior region of the trunk, close behind
the gill- slits, and about midway between the dorsal and ventral
contours. The shoulder girdle to which they are attached
(§§ 7° — 74) can be felt immediately behind the gill-slit. If
the pectoral fin be made to stand out at right angles to the
body, it will be seen to have a dorsal surface looking
upwards and backwards, a ventral surface, downwards
and forwards, a strong, straight pre-axial border towards
the head, and a thin curved post-axial border towards the
tail. When left to itself, it lies with its dorsal surface against
the side of the body and its pre-axial border looking upwards.

96. The pelvic or so-called ventral fins (hind-limbs)
(Pv-f)t small fins situated below and slightly in front of the
pectorals : the pelvic girdle (§77) to which they are attached
can be felt in the angle between the ventral ends of the
shoulder girdles. The surfaces and borders of the pelvic
fins have the same names as those of the pectorals, and are
easily identified.

XVII.1 Carefully dissect away the skin from the left
side of the body, observing the following : -

The following sections (§ XVII — 99) may be omitted until after the
dissection of the viscera, and then worked out on the right side of the
body.

loS ZOOTOMY.

97. The body muscles (Fig. 30), distinctly divided into
vertical segments or myotomes, separated from one
another by septa of connective tissue : each myotome takes
a zigzag course, passing, from the middle dorsal line, at first
sharply backwards, then gently forwards, then gently back-
wards, and finally sharply forwards to the middle ventral
line. The myotomes are also more or less distinctly
divided into dorsal and ventral portions : the dorsal
muscles on nearing the head, turn forwards, and are inserted
into the frontals ; the ventral muscles being inserted into
the clavicles.

98. The cutaneus quinti ( T), or cutaneous branch of the tri-
geminal nerve (§ 193), seen emerging from between the muscles on
the dorsal surface of the head, and passing backwards and slightly out-
wards immediately beneath the skin. Soon after its origin it gives off
two or three small nerves which pass backwards and upwards, and,
uniting with one another form a trunk ( V] which runs along the bases
of the dorsal fins, as far as to the caudal. The main trunk of
the cutaneus quinti divides into two branches, one of which ( V")
passes downwards and backwards to the anal fins, supplying them in
the same way as the dorsal branch supplies the dorsal fins : the other
(V'"} passes along the outer face of the clavicle and sends branches to
the pectoral and pelvic fins. Traced forwards, the cutaneus quinti is seen
to make its exit from the skull by a foramen in the parietal (§ 31).

99. The cutaneus vagi, or cutaneous branch of the pneumogas-
tric nerve (§ 196), emerging from beneath the operculum near its dorsal
end, having already divided into two trunks, which pass almost directly
backwards, the first {X} immediately beneath the skin of the lateral
line, the other (A") along the line of junction of the dorsal and ventral
muscles ; at about the level of the second dorsal fin these nerves begin
gradually to approach one another, and 1 he upper one soon fades off, the
lower one then passing along the lateral line to the tail. The two
trunks are united by one or two commissures.

XVIII. Keeping the fish with its left side uppermost,
make a median ventral incision from the hip-
girdle backwards to within a quarter of an inch of

THE COD, 107

the anus. Take a second incision passing verti-
cally dorsalwards from the anterior end of the
first, and a third sloping obliquely backwards and
upwards from its posterior end : carefully lift up
the flap of muscle as you make these cuts so as to
be sure that none of the internal organs are
injured. Extend both cuts upwards until the
body cavity is well exposed : then fasten back or
remove the flap of muscle. Observe the following
points without further dissection :-

100. The abdominal cavity, enclosed by the muscular
walls of the body, ending in front at about the level of the
shoulder girdle, and extending posteriorly for a short distance
behind the anus.

10 1. The peritoneum (parietal layer), a pigmented mem-
brane lining the abdominal cavity. The visceral layer of
the peritoneum is reflected over the viscera (see § no),

102. The liver (Fig. 31, ?r), a large brown-coloured
organ, with its broad attached end at the anterior boundary
of the abdomen and its long left (/;-3) and short right (/r1)
and middle (/;-2) lobes extending backwards towards the
posterior end of the cavity.

103. The stomach (Fig. 31, sf}, a wide thick-walled tube,
passing from the front wall of the abdomen, backwards to
within a short distance of the anus, where it becomes bent
forwards upon itself : in the undisturbed position of the
parts it is largely covered by the liver.

104. The intestine (Fig. 31, dm., //., rcf], a coiled tube,
connected anteriorly with the recurved portion of the
stomach, and ending behind in the anus (see § 119).

105. The pyloric caeca (Fig. 31, py.c] numerous small
blind tubes, arranged in bunches around the small intestine
at its junction with the stomach.

loS

ZOOTOMY.

106. The spleen, a smooth, dark red body, of elongated
form, 'situated somewhat dorsal to, but not directly con-
nected with the stomach.

107. The gall-bladder (Fig. 31, g.b), a large ovoid sac,
filled with bright green bile, situated about the middle of
the abdominal cavity towards the right side.

ret

hA

pij.c

FIG. 31. — Gadus morrhua. Dissection of the alimentary canal
and its glands, from the right side (\ nat. size).

a, anus : c.b.d, common bile duct : c.d, cystic duct : dm, duodenum :
g.b, gall-bladder : /;.</, hepatic duct : il, ileum : //-1, right lobe of liver :
!r~, middle lobe of liver : 7;-3, left lobe of liver : as, oesophagus :
py.c, pyloric caeca : ret, rectum : st, stomach : x, aperture of bile
duct, below it apertures of pyloric coeca.

1 08. In the male, the testes, long lobulated glands,
having much the appearance of fat, and extending horizon-
tally along a considerable proportion of the length of the
abdominal cavity : their size varies greatly according to the
season and the age of the fish.

109. In the female, the ovaries, conical sacs, of a pink

THE COD. 109

colour, situated in the posterior part of the abdominal
cavity, above the termination of the intestine.

no. The visceral layer of the peritoneum, a thin trans-
parent membrane, enveloping, somewhat loosely, the fore-
going viscera.

in. The air-bladder or swim-bladder, covering the
whole of the dorsal wall of the abdomen, the peritoneal
lininsr of which is continued over its ventral surface: if in

O

the distended condition, its smooth median and sacculated
lateral regions render it readily distinguishable ; if collapsed,
it is less obvious.

112. The ureter, a thin-walled tube, passing upwards
from the urinary aperture to the posterior end of the air-
bladder to join the kidney, which is at present concealed :
near its ventral end it gives off a bilobed diverticulum, the
urinary bladder.

XIX. Continue forwards the median ventral incision
already made, by cutting through the hip-girdle
and between the right and left halves of the
shoulder-girdle : dissect away the left half of both
pectoral and pelvic girdles, working from below
upwards, and taking especial care not to cut too
deeply and so run the risk of injuring the hepatic
(§ 125) and precaval (§ 141) veins. Note

113. The gullet (Fig. 31, as], a tube of about the same
diameter as the stomach, with which it is continuous
posteriorly, while in front it passes into the pharynx
(§XXX.).'

114. The pericardial cavity; a small chamber con-
taining the heart (§ 115) and separated by a strong fibrous
partition -- the pericardio-peritoneal septum — from
the cavity of the abdomen : it is bounded above by the floor
of the mouth and bases of the gills, and below by the

i io ZOOTOMY.

ventral ends of the clavicles and the muscles in connection
with them.

115. The heart (Fig. 32), consisting of (a) the small,
thin-walled sinus venosus (s. v\ attached by the hepatic
veins (§ 125) to the pericardio- peritoneal septum; (b) the
large, irregular thin-walled auricle (ait), situated in the
dorsal region of the cavity, and largely concealing (c) the
firm, prismoidal ventricle (v), which lies in the ventral
region of the pericardial cavity and passes in front into (d)
the white, rounded bulbus arteriosus (b.a).

1 1 6. The pericardium, a thin membrane lining the
pericardial cavity and reflected over the heart in the same
manner as the peritoneum over the abdominal viscera.

XX. Skin the top of the head and clear away the
muscles until the roof of the skull is exposed :
break away the latter, bit by bit, with bone forceps
or strong scissors, and observe

117. The brain, lying loosely in the large cranial
cavity, and continuous posteriorly with the spinal cord,
which passes through the neural canal of the vertebral
column to the tail.

118. The arachnoid fluid filling the space between the
brain and the walls of the cranial cavity.

Large cod are often killed by a blow on the head ; this gives rise to
extensive extravasation, and the cranial cavity is found to be full of
clotted blood, which adheres so closely to the brain as to require care in
its removal.

XXI. If no second specimen is to be dissected, go over
§§ XXXVI — 196 : then cut through the spinal cord
about half an inch from its junction with the
brain, sever the various cranial nerves, carefully
detach the olfactory lobes from their attachments
(§ 189), remove the brain, and place it in alcohol

THE COD. in

of about 90 per cent. If a second specimen is to be
dissected, the examination of the external features
of the brain may be postponed, and the organ
placed in alcohol at once.

XXII. Place the fish once more on its right side, and
by turning forward the lobes of the liver, and,
when necessary, dissecting away the peritoneum
from the viscera, blood-vessels, £c, make out the
following : -

119. The divisions of the alimentary canal (Fig. 31) : the
oesophagus passes insensibly into the stomach, the cardia
or aperture of communication between the two being marked
only by a difference of colour and texture ; the stomach
passes back to the hinder end of the abdomen, becomes
bent upon itself towards the right side, and narrowing,
becomes continuous with the small intestine, the pylorus
or aperture of communication between the two being marked
by the attachment of the pyloric caeca (py.c) ; the first loop
of the intestine is U-shaped and represents the duodenum
(din) ; this is followed by the ileum (//), which after a

1 The injection of the blood-vessels, which is necessary for their
satisfactory examination, is best performed in the following way : (a)
Make a small incision into the bulbus arteriosus, and insert a cannula
directed forwards ; from this the ventral aorta and afferent branchial
arteries are injected : (b) insert a second cannula into one of the branches
of the me.-enteric artery, e.g. that supplying the pyloric caeca, directing
it forwards, or towards the proximal end cf the artery ; from this the
dorsal aorta and efferent branchial arteries are filled : (c) a third can-
nula is inserted into one of the factors of the portal vein, e.g. that
corning from the pyloric caeca, its point being directed forwards cr
towards the main portal vein, which is in this way thoroughly injected :
(d] a fourth cannula is inserted, pointing forwards, into the spermatic
vein (§ 126) ; from this the main systemic veins are easily filled. Plaster
of Paris, or some other cold injecting material, must be used ; as a very
slight heat causes gelatinization of the connective tissue of the blood-
vessels and their consequent rupture.

ii2 ZOOTOMY.

minor turn, forms a long loop enclosed in a special invest-
ment of peritoneum and extending backwards posterior to
the anus ; passing forwards again, the ileum forms a loop
within and concentric to that of the duodenum, and is then
continued insensibly into the rectum (rct\ which is only
marked by its somewhat greater diameter and by the dark
colour of its contained faeces ; the rectum passes directly
backwards to the anus (#), between the ileum on the right
and the stomach on the left.

120. The way in which the viscera are supported by
folds of peritoneum : the stomach is suspended to the
dorsal wall of the abdomen by a vertical fold, the meso-
gaster : a similar fold supporting the small intestine is the
mesentery : one suspending the rectum is the meso-
rectum : the testes are kept in position by the mesorch-
ium, the ovaries by the mesoarium : the anterior border
of the liver is connected to the anterior wall of the abdo-
men by the coronary ligament and its dorsal surface is
connected with the stomach by the gastro-hepatic
omentum.

121. The cystic duct (Fig. 31, c.d) from the gall-bladder
(g.b), joined by several hepatic ducts (/i.d) from the liver :
from the point of junction the common bile duct (c.b.tf)
passes backwards and opens into the small intestine just
beyond the pylorus.

122. The portal vein (Fig. 32, p], taking blood from the other
abdominal vi- cera to the liver : it is a large vein receiving factors from
the stomach, intestines, spleen, and pyloric coeca, as well as a branch
from the air-bladder, leaving the wall of the latter at about the junction
of its anterior and middle thirds, and bringing blood from the rete
mirabile (x) (vide infra § 139). All these tributaries unite to form
a plexus of large veins in the gastro-hepatic omentum, from which
several veins go off into the substance of the liver (^').

123. The gastric branch of the vagus (tenth cerebral) nerve, a

THE COD. 113

large nerve entering the abdomen alongside the gullet and spreading
out into a number of fine branches on the surface of the stomach.

124. The cceliac and mesenteric arteries (Fig. 32, cce, m), entering
the abdomen above and to the right of the gullet : the former goes
almost exclusively to the pyloric caeca : the mesenteric artery supplies
the stomach (g], intestines (/), spleen (spl], andrete mirabile (x}.

125. The two hepatic veins (Fig. 32, hp) proceeding, one on each
side, from the anterior border of the liver, through the pericardio-peri-
toneal septum to the sinus venosus.

126. The spermatic vein (Fig. 32, sp.v] bringing blood from the
ovary or testis, from the anterior end of which it passes directly forwards
to join the precaval vein (§ 141) : the spermatic artery (sp.a) arises
from one of the gastric branches of the mesenteric.

XXIII. Remove the liver, stomach, intestine and
spleen : cut open the stomach and duodenum,
wash out their contents and note

127. The rugce of the stomach, prominent longitudinal
folds into which its mucous membrane is thrown.

128. The pyloric valve, a circular ridge of mucous
membrane forming a constriction between the stomach and
intestine.

129. The aperture of the bile-duct (Fig. 31, x) in the
duodenum, near the pyloric valve : a bristle should be
passed from it into the duct.

130. The three or four openings of the pyloric caeca
(Fig. 31, below ,v), situated in the duodenum between the
pylorus and the bilary aperture.

XXIV. Make out the following points in the repro-
ductive organs, still left in situ :-

In the Male.

131. The testes, two elongated bodies, each consisting
of a straight tubular axis, the vas deferens, with a soft
greatly lobulated body, the testis proper, attached to the
whole length of one side. At about one fourth of their
length from the posterior end, the two testes unite with

i

ii4 ZOOTOMY.

one another in the middle line, and send off a short common
duct, which passes, closely attached to the front wall of the
ureter, to the genital aperture.
./// the Female.

132. The ovaries, two conical bodies, united with one
another posteriorly and sending off from the point of junc-
tion a short oviduct which passes downwards between the
ureter and the rectum to the genital aperture.

XXV. Remove the reproductive organs and the ureter
from the body, along with a small portion of
the body wall containing the urinary and genital
apertures : in cutting through the ureter leave a
recognisable piece of its dorsal end, as it will
have to be traced to the kidney (§ 143) : pin
out these organs under water, and make longi-
tudinal incisions though the ureter and the vas
deferens or oviduct and ovary ; note

133. A median partition dividing the dorsal end of the ureter into
two tubes.

/// the Male.

134. The common genital canal, receiving the vasa
deferentia, opening externally by the genital aperture, and
separated by a thin partition from the ureter.

135. The numerous small apertures in the vas deferens
by which it receives the secretion from the lobes of the
testis.

Jji the Female.

136. The large central cavity of the ovary, encroached
on by irregular processes of the substance of the organ, on
which the ova are developed.

137. The cavity of the oviduct, continuous with those of
the two ovaries, and opening externally by the genital
aperture.

THE COD. 115

XXVI. Open the air-bladder by a longitudinal incision
along its left side, and dissect away the muscles,
&c., which still obscure its anterior end, taking
care not to injure the precaval vein (§ 141) ; note

138. The characters of the air-bladder: its lateral and
ventral walls are very thick and tough, its dorsal wall so
thin chat the vertebral column, aorta (§ 142), and kidneys
(§ 143) can be readily seen through it ; its ventro-lateral
portions are deeply sacculated, and its antero-lateral angles
produced each into a long coiled tube, blind at its free end ;
of these the left only is seen at present, imbedded among
the muscles at the anterior end of the air-bladder.

139. The rete mirabile of the air-bladder, a large, soft,
cake-like mass of rounded outHn-e and red colour, situated
within the air-bladder in contact with its ventral wall : as
already seen, it receives a branch from the mesenteric artery
and pours its blood into the portal vein.

140. The anterior portion of the kidney — usually called
the head-kidney — a dark-brownish red mass, lying above
and in front of the anterior end of the air-bladder.

141. The (left) precaval vein (ductus CitTierii) (Fig. 32,
pc], a large vein passing from the sinus venosus upwards
to the anterior part of the kidney, crossing the gullet as it
goes, and lying immediately behind the last branchial arch ;
it receives the corresponding spermatic vein, and at its
dorsal end is formed by the confluence of two veins, the
left jugular bringing the blood from the head, and the
left cardinal returning that from the trunk generally.

142. The dorsal aorta (Fig. 32, d.ao\ a large median
artery, seen through the thin dorsal wall of the air-bladder;
to show it plainly, the latter should be dissected away.

The dorsal aorta is continued posteriorly as the caudal artery (c.a),
which passes through the haemal arches of the tail ; before doing so it

I 2

n6 ZOOTOMY.

gives off an artery (y) which passes downwards alongside the ureter
(§ 112) to supply the bladder, anterior anal fin and body muscles of that
region, and also anastomoses with the intestinal artery (t) by a small
branch.

143. The kidneys, consisting of two irregular longi-
tudinal bands of soft reddish-brown tissue, lying one on each
side of the aorta ; to see them satisfactorily, the dorsal wall
of the air-bladder must be dissected away ; anteriorly they
pass each into the so-called head-kidney already seen (§ 140) ;
posteriorly they unite and form a large median mass, lying
immediately behind the air-bladder and enclosed in the
haemal canal of the anterior caudal vertebrae, which must
be cut away to display it ; it is from this hinder part of the
kidney that the unpaired ureter springs.

144. The cardinal vein (Fig. 32, l.cd, r.cd), a somewhat
irregular trunk, running through the substance of each
kidney.

The middle part of the left cardinal is aborted for some distance, the
veins from the left kidney in this region passing into the right cardinal.1
Posteriorly, the two become continuous with the caudal vein (c.v),
which parses through the hsernal canal, ventral to the caudal artery. A
vein (y] bringing back the blood from the posterior part of the air
bladder, urinary bladder, anterior anal fin and body-wall, and anasto-
mosing with the portal, runs parallel to the corresponding artery (§ 142),
and enters the caudal vein just as it emerges from the haemal canal.

145. The sympathetic nerve is also imbedded in the kidney.

XXVII. Dissect away the muscles, &c lying in front
of the heart and at the bases of the gills, and bring
into view

146. The ventral aorta (Fig. 32, v.ao), passing forwards
from the bulbus arteriosus and ending abruptly at about the
level of the ventral end of the first gill.

1 Its anterior part is sometimes connected with the right cardinal by a
transverse anastomosis in this region.

THE COD.

117

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nS ZOOTOMY.

The hyoidean (§ 175) and two first efferent branchial arteries (§ 158)
anastomose at their ventral ends, and from the junction of the two
latter an artery is given off on each side, which meets with its fellow
below the ventral aorta to form an azygous vessel, which is best seen at
this stage. This soon divides into two branche?, one of which passes
above, the other below, the pericardium, supplying the muscles in
these regions, and giving off several very small coronary vessels to the
heart (Fig. 32, co). The ventral branch eventually divides into two,
which supply the pelvic fins (pi}.

147. The afferent branchial arteries (Fig. 32, a.br^,
.a.br^}, four on each side, given off laterally from the ventral
aorta to the four pairs of gills, and passing dorsalwards
along the posterior face of the corresponding branchial
arches.

148. The inferior jugular vein (Fig. 32, i.jii], an unpaired vein
bringing the blood from the lower parts of the head : it passes through
the pericardial cavity to the dorsal side of the heart, and opens into
the right precaval.

XXVIII. Remove the heart and observe again the
relations of its parts (§ 115); then open its
various chambers by the removal of the left
wall of each. This is best done • under water.
Observe

149. The thin smooth walls of the sinus venosus.

150. The sinu-auricular valve, between the sinus
venosus and the auricle; it consists of two membranous
flaps, respectively dorsal and ventral in position.

151. The thin walls of the auricle, strengthened by a
network of interlacing muscular bands, the musculi
pectinati.

152. The auriculo-ventricular valve, guarding the
round aperture between the auricle and the ventricle ; it
consists of two flaps, respectively anterior and posterior in
position!

THE COD. 119

153. The thick muscular walls of the ventricle, raised
internally into a network of ridges, the colurnnse carneas.

154. The aortic valves, consisting of two semilunar
flaps situated right and left, at the junction between the
ventricle and the bulbus arteriosus.

155. The thick fibrous walls of the bulbus arteriosus.

XXIX. Draw the gills of the left side downwards, so
as to feel the muscles (levatores arcuum branchi-
alium) connecting them with the skull on the
stretch : dissect away these muscles, as well as the
anterior part of the air-bladder, make out

156. The branchial branches of the vagus, distributed to the bran-
chial arches in the same manner as in the Skate (p. 82, § 214). The origin
of the gastric, cardiac, and cutaneous branches of the vagus may Le seen
at the same time, as well as its exit from the skull (see § 196).

157. The glossopharyngeal, dividing, soon after its exit from the
skull, into two branches, a posterior going to the anterior face of the
first branchial arch, and an anterior passing at first forwards, and then
downwards, along the inner face of the hyomandibular to the pseudo-
branch (§ 196).

158. The left epibranchial artery (Fig. 32, ep.br),
lying longitudinally along the dorsal ends 'of the gill arches,
and receiving the four efferent branchial arteries
(ef.br.1, ef.br.*), one from each arch. After receiving the
last efferent artery the epibranchial trunk passes inwards
and backwards, and unites with its fellow of the opposite
side to form the dorsal aorta, but just before doing so, it
gives off a subclavian artery (s.d) on each side, which
supplies the pectoral fin. The cceliac (cat) and mesen-
teric (m) arteries (§ 124) arise from the right epibranchial
just anterior to the subclavian.

XXX. Cut through the lower jaw, the hyoid, and the
branchial arches, a little to the left of the middle
ventral line, so as to leave the tongue intact on

120 ZOOTOMV.

the right side ; place the fish in the supine
position (dorsal surface downwards) and fasten
out the mandible, hyoid, and gill arches right and
left, so as to get a good view of the interior of the
mouth. Observe the following :-

159. The numerous small premaxillary teeth arranged
in two symmetrical sets on the premaxillse.

160. The larger mandibular teeth on the lower jaw.

161. The median cre-scentic group of vomerine teeth,
a short distance behind the premaxillary teeth.

162. The superior pharyngeal teeth, arranged in
four groups, two on each side, on the ankylosed pharyngo-
branchials (§ 57).

163. The inferior pharyngeal teeth, one group on
each of the small fifth branchial arches (§ 62).

164. The small, blunt, non-protrusible tongue, supported
by the median ventral portion of the hyoid arch.

165. The absence of posterior nares or spiracles.

1 66. The branchial clefts, vertical fissures between
the gill arches, five in number, the first being between the
hyoid and first branchial arches, the last between the fourth
and fifth branchials.

167. The gill-rakers, horny filaments acting as strainers,
attached to the branchial arches, and bounding the margins
of the clefts.

1 68. The greatly constricted aperture of the oesophagus.

169. The pseudobranchia has been already noticed
(§ 90) : on removing the mucous membrane, it is seen to
be a rounded vascular body, resembling the rete mirabile
in the air-bladder.

XXXI. Remove a portion of one of the gills on the
left side, and make out by dissection and trans-
verse sections

THE COD. 121

170. The bony branchial arch, supporting the gill
along its whole length, and having a crescentic transverse
section.

171. The form and arrangement of the branchial fila-
ments: each has the form of a right-angled triangle with
a very narrow base attached to the branchial arch, and with
the apex free : the hypotenuses face opposite ways in suc-
cessive filaments, so that while the bases of the filaments form
a single row, their free ends form a double row, each row
corresponding with a demibranch in the skate (p. 46, § 84).

172. The complete freedom of the branchial filaments
owing to the absence of partitions, such as are found in the
Skate (p. 45, § 83, and p. 69, §§ 164, 165).

173. The afferent and efferent branchial arteries, running
parallel with one another along the outer side of the
branchial arch, the afferent artery being external : the
branches of the afferent artery go to the inner sides (hypo-
tenuses, § 1 7 1 ) of the gill filaments, the feeders of the effer-
ent artery lie along their outer sides.

XXXII. Keeping the fish in the supine position, dissect away the
pharyngobranchials of both sides sj as to expose both epi-
branchial arteries ; trace forward the latter, and dissect away
enough of the mucous membrane to make out the following :

174. The carotid arteries (Fig. 32, c), continuing forwards the
epibranchial trunks, and uniting with one another above the parasphe-
noid by a short, slender, transverse trunk, thus completing the circulus
cephalicus.

175. The hyoidean artery (Ft*. 32, hy), springing from the ventral
end of the first afferent branchial, and dividing into two branches, one
of which forms the afferent artery of the pseudobranch (/j), while the
other anastomoses with the epibranchial (ep.br}.

The blood is collected from the pseudobranch by an efferent (ophthal-
mic) artery (op), which, after curving over the corresponding carotid,
and anastomosing with its fellow of the opposite side by a short trans-
verse trunk immediately in front of the carotid anastomosis, passes to
the choroid gland of the eye (§ 178).

122 ZOOTOMY.

176. A nerve running alongside the hyoidean artery is the posterior
or hyomandibular division of the seventh nerve or portio dura.
(See§ 193.)

XXXIII. Remove the layer of transparent integument covering
the exposed surface of the eye ; cut away the supraorbital
process of the frontal with bone forceps, and, if time permit,
dissect out the ocular muscles and their nerves, which have
the same essential disposition as in the skate (pp. 77, 78, §§ 191
— 203) ; then remove the eye, dissect away the muscles, &c. still
attached to it, and divide it into inner and outer hemispheres by
an equatorial incision, passing midway between the pupil and
the entrance of the optic nerve. Note the following : —

177. The cornea, iris, lens, sclerotic, retina, and aqueous and
vitreous humours, have the usual relations (pp. 84, 85, §§ 224 — 228).

178. The choroid, consisting of three distinct layers ; a black pig-
mentary layer next the retina, a shining silvery layer next the sclerotic
and between these a red vascular layer, which undergoes a great
thickening around the entrance of the optic nerve, forming a sort of
annular cushion ; this thickening is the so-called choroid gland.

179. A slit in the retina extending from the blind spot or entrance of
the optic nerve, along the posterior (outer) side of the eyeball to the
ora serrata or outer boundary of the retina ; through it extend a deli-
cate grey fold of the choroid, the processus falciformis, which ends
against the posterior side of the lens in a pyrifoim enlargement, the
campanula Halleri.

XXXIV. The fifth nerve may now conveniently be dissected
(§ 193) 5 afterwards remove the skin in the neighbourhood of
the nostrils, and observe

i So. The small nasal sac, communicating with the exterior by the
two apertures already seen (§ 86), but having no connection w'ith the
mouth : its wall is formed by the delicate, plaited Schneiderian
membrane.

XXXV. Carefully break away the roof of the auditory capsule so
as to expose the organ of hearing ; or, better, remove the
entire auditory capsule, fasten it out firmly under water in a
dissecting-clish and dissect it from the inner or cranial side.
Note

1 8 1. The irregular system of cavities excavated in the bone and
cartilage of the auditory capsule for the membranous labyrinth ; the
separation of these cavities from the brain cavity by membrane only.

182. The membranous labyrinth (Fig. 33), consisting of the ovoidal

THE COD. 123

vestibule (r) and of the three semicircular canals : the latter have
the usual arrangement; the anterior (a.s.c) and posterior (p.s.c) canals
have their adjacent limbs confluent, so that the two canals open by three
apertures into the vestibule ; the horizontal canal (h.s.c) lies entirely to
the outer side of the vestibule, into which it opens by two separate aper-
tures, and the ampullx (a) are situated at the actual extremities of the
canals, those of the anterior and horizontal canals being anterior,
that of the posterior canal posterior.

183. The two otoliths, one large (s) and shaped something like a
shell (sagitta), and the other very small (at) (asteriscus) lying in a small
diverticulum of the vestibule, just beneath the ampulla of the posterior
canal.

G..S.C

8

FIG. 33. — Gadus morrhua. The organ of hearing. (From a
sketch by Mr. G. B. Howes.)

z/, vestibule: a.s.c, anterior, p.s.c, posterior, and h s.c, horizontal,
semicircular canals : a, a, a, ampullae: s, sagitta : as, asteriscus.

XXXVI. Examine the brain : if a fresh fish is used for
the purpose and no spirit-specimen is available,
the verification of the characters of the ventral
surface must be left until the origins of the nerves
have been made out, when the brain may be
removed : note the following :—

184. The medulla oblongata (Fig. 34, m.o\ or hind-
most division of the brain, continuous with, and of scarcely
greater diameter than, the spinal cord.

I24 ZOOTOMY.

Its dorsal surface is marked with an obscure longitudinal furrow,
continuous with the dorsal fissure of the cord, and separating two
longitudinal elevations, the posterior pyramids, external to which are
two similar elevations, the restiform bodies.

185. The cerebellum (crb\ a large tongue-shaped
body, lying on the dorsal side of the medulla oblongata,
and largely concealing it in a view from above. The medulla
and cerebellum together form the hind-brain.

1 86. The mid-brain, consisting on the dorsal side of
two considerable ovoidal masses, the optic lobes (<?./),
and below of a mass corresponding to the crura cerebri
(r.f), of other vertebrate brains.

187. The fore-brain, consisting mainly of the two
cerebral hemispheres (c./i), irregular rounded masses,
situated just anterior to the optic lobes, and of considerably
smaller size than the latter : each hemisphere is marked
dorsally with a furrow or sulcus parallel to its inner edge.
A small somewhat rhomboidal area in the middle line,
between the hemispheres and optic lobes, is all that appears
externally of the 'twixt-brain or thalamencephalon,
above; below it is constituted by two somewhat bean-shaped
bodies, the lobi inferiores (/./), and the infundibulum
(/>/), lying between them (see § 205). On slightly separating
the hemispheres they are seen to be united by a delicate
transverse commissure (cm) passing between their inner faces.

1 88. The pituitary body (//), a rounded vascular mass,
of deep red colour, situated in the middle ventral line
immediately beneath the thalamencephalon.

189. The olfactory lobes (0/f), two rounded bodies,
each about two-thirds the diameter of one of the cerebral
hemispheres, situated in close contact with the hinder walls
of the nasal sacs, and connected by delicate nerve-like cords
(I) with the corresponding hemispheres : the connecting

THE COD.

L-5

m.o

FIG. 34. — Gadus morrhua. The brain, A, from above ; B, from
beneath ; C, from the left side ; D, longitudinal vertical section ; E,
with the ventricles laid open from above, by the removal of the greater
part of the cerebellum (crb) and of the optic lobes (o.l) ; the cerebral
hemispheres are also cut through horizontally to show the absence of
lateral ventricles, and the commissure (cm) by which the hemispheres
are united (nat. size).

aq.s, aqueduct of Sylvius ; c.c, crura cerebri : c.h, cerebral hemis-
pheres : cm, commissure between hemispheres : cm', commissure be-
tween lobi posteriores : crb, cerebellum : f.G, fornix of Gottsche : in,
inmndibulum : /./, lobi inferiores : l.p, lobi posteriores: m.o, medulla
oblongata : o ./, optic lobes : elf, olfactory lobes : //, pituitary body :

I26 ZOOTOMY.

O, tori semicirculares : z/.3, third ventricle : z/.4, fourth ventricle : JT,
valve-like flap covering anterior part of aqueduct of Sylvius : /,
peduncles of olfactory lobes : //, optic nerve : ///, third nerve : IV,
fourth nerve : V, fifth nerve : V1, orbitonasal nerve : V-3-, maxillary
nerve: P2b, palatonasal nerve: V*, rnandibular nerve: Vc, cutaneus
quinti : VI, sixth nerve : VII, seventh nerve : VIII, auditory nerve :
IX, glossopharyngeal ; X, vagus : Xc, commissure between fifth and
tenth nerves.

cords are single in the anterior, double in the posterior part
of their course.

190. The large strap-like optic nerves (II), arising
from the ventral surface of the brain, immediately in front of
the optic lobes : they pass at first directly forwards, then
cross one another, the right nerve going to the left eye, and
vice versCi : they make their exit from the cranial cavity
through foramina in the membranous side-walls of the
skull.

191. The third pair of nerves (oculomotor, III),
arising from the ventral surface of the mid-brain, external to
the lobi inferiores and passing to their foramina in the mem-
branous wall of the skull some distance posterior to the
optic foramina.

192. The delicate fourth pair of nerves (pathetic, IV),
arising from the dorsal surface of the brain, between the
optic lobes and the cerebellum, and leaving the skull a little
above the optic foramen.

193. The fifth (trigeminalj V) and seventh (facial or
portio dura, VII) nerves, arising together from the anterior
part of each side of the medulla oblongata, and leaving the
cranial cavity by the trigeminal notch in the prootic (§ 27).

The fifth nerve early divides into the three characteristic divisions :
the first of these (orbitonasal, V1) passes forwards and upwards along
the inner wall of the orbit, over the optic nerve, and supplies the parts
about the snout : the second division (maxillary, V'2a) passes outwards

THE COD.

T ->'-

- -/

and forwards, the greater part of it going to the upper jnvv ; a branch
given off near its origin (palatonasal, V-b) 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 (Vc)
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.

1 he vagus, on leaving the skull, sends off branchial nerves which
supply the branchial arches in the same manner as in the skate (p. Si,
§ 214), it then divides into two trunks, one passing ventral wards 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 (Xc).

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 (/./), a pair of rounded
elevations on the anterior part of the floor of the fourth
ventricle, and between them a large transverse commissure
(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
optic lobes 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 (t.s), two somewhat
kidney-shaped elevations, situated, one on each side on the
floor (cms cerebri) (c.c) of the optic ventricle.

201. The fornix of Gottsche (/£)> 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 (x\ 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 (aq.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

i

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 (///) 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.1

THE GREEN LIZARD (Lacerta viridis\

THE SAND LIZARD (L. agilis).

THE SCALY LIZARD (Zootoca vivipara].

(A).— THE SKELETON.

I. The skeleton of the lizard may be prepared either
by maceration, i.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. 131

well to make a longitudinal vertical section of it
with a fret-saw. In the other skeleton the bones
should be disarticulated, the vertebrae 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 J to i 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 vertebrae, divisible into (a) a cervical region
of eight vertebrae, forming the skeleton of the neck ; (b) a
thoracico-lumbar region of twenty-two vertebrae, forming,
with the ribs and sternum, the skeleton of the trunk : (c) a
sacral region of two vertebrae, giving attachment to the
pelvis : and (d} a caudal region, consisting of a variable
number of vertebras supporting the tail.

2. The skull, articulated to the first cervical vertebra,
and consisting of (a) the brain-case and upper-jaw :
(b) lower-jaw, composed of two separate rami : and (c)
the hyoidean apparatus supporting the tongue.

3. The ribs, springing in pairs from many of the vertebrae :
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

*J i •

anterior thoracic region, to the vertebrae 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
vertebrae.

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 vertebrae :
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, backvvardly 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
vertebrae, 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 vertebrae:
each fits by the concave anterior fac,e of its centrum against

THE LIZARD. :•;?

w -J

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 vertebras, due to the fact that
each neurapophysis is notched, slightly in front, more deeply
behind.

13. The cervical vertebrae, 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.

1 6. 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 vertebras differ but

134 ZOOTOMY.

little from the anterior or true thoracic, save for the fact that
their centra are somewhat shorter.

1 8. The sacral vertebrae, distinguished by their short
centra, and by the presence of large, expanded, outwardly
directed transverse processes, against which the ilia
(§ 10 1 ) 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 vertebrae,
is somewhat less marked than in the other vertebrae : the
posterior convexity of the second sacral is more than usually
pronounced.

19. The anterior caudal vertebrae 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 vertebrae 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 vertebra; but a few of the anterior 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
vertebrae, but consists of an unjointed calcined 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 (sf) : 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 vertebrae 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, /;;/), a median
rounded aperture on the hinder surface of the skull, leading
into the brain cavity.

31. The occipital condyle (Figs. 35 and 37, o.c), a
rounded surface beneath the foramen magnum, articulating
with the atlas.

32. The posterior temporal fossae, 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.oc\ 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 fossae, 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.

'37

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, t.o.s), a
plate of cartilage forming a median vertical partition between
the orbits (§ 69).

ep.o

.9.0

en

op.o
K.X.XL

FIG. 35. — Lacerta agilis. Longitudinal ve-tical section of the
skull (after W. K. Parker, slightly altered) X 4. The cartilaginous
parts are distinguished by dotting, the membranous spaces by cross-
hatching.

als, alisphenoid : b.o, basioccipital : b.pt, basipterygoid : b.s, ba.si-
sphenoid : e.o, exoccipital : ep.o, epiotic ; e.pt, epipterygoid : fa, fon-
tanelle : fr. frontal: i.o.s., interorbital septum: na, nasal: o.c, occi-
pital condyle : op.o, opisthotic : pa, parietal \pa.s, parasphenoid : p. mx,
p-emaxilla : pr.o, prootic : s.mx, septo-maxillary : s.n, septum nasi •
s.o, supraoccipital : i-o, vomer . I — XII, foramina for exit of the cere-
bral nerves.

3'

19. 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, pa\ 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 (fo] : 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.

41. The frontals (/;•), 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 (no), paired bones extending from the
anterior border of the frontals to the posterior border of the
anterior nasal fossa.

43. The premaxilla (p.mx), 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
fossae, 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 maxilla, 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.

50. 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.

51. The supratemporals, two bones on each side, of
which the first overlaps the posterior edge of the postorbital,

1 4o 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 latter 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, />.<?), a median bone
forming the posterior part of the basis cranii, and furnishing
the middle third of the occipital condyle (o.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, (e.o)
(posterior portion), and opisthotic (op.o) (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 (s.o), its lateral portions represent the
epiotics (ep.o.).

57. The prootics (pr.o\ 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, a.s.c,
p s.c, k.s.c).

THE LIZARD. 141

59. The basisphenoid (Fig. 35, b.s), 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 (b.pt\ its front edge is continued into
a delicate bony style, the parasphenoid (pa.s\ 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 fossae : 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 (uo\ 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.

H2 ZOOTOMY.

64. The epipterygoid (e.pt.) (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 columella 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.

i.at

jf CM

FIG. 36. — Lacerta agilis. The columella auris (after W. K. Parke?)
x 14. The cartilaginous parts are dotted.

e.st, extra- stapedial : i.st, infra-stapedial : m.st, medio-stapedial :
s.st, supra-stapedial : st. 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, (st), a small cartilaginous nodule in the fenestra ovalis : (b) the
medio-stapedial (m.sf), a bony bar connected with the stapes, the
ossification from it extending into the latter : (c) a. cartilaginous rod
continuous with the distal end of the medio-stapedial, sending off a
downwardly directed process, the infra-stapedial (i.st), 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 (e.st) : its dorsal extremity, the supra-
stapedial (s.st) 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, loth, and nth cerebral nerves: the i2th
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, voiners,
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 (Figs. 35, 37. i.o. s), 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.n\ to the end of the snout,
forming the partition between the nasal sacs ; the dorsal edge of the
interorbital septum closely underlies the anterior part of the brain,
and gives off, on each side, a partly cartilaginous partly membranous
plate, directed upwards and outwards, which, uniting behind with the
prootic, above with the skull roof, and in front with the descending
processes of the frontals, furnishes a side-wall to the anterior part
of the brain-case : the interorbital septum and its wings have in trans-
verse section the form of a Y. Paired ossifications in the posterior part
of the membrano-cartilaginous skull walls represent the alisphenoids (al.s).

70. The nasal capsules (Fig. 37, no), 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

Ixl-1.

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-

s.n

-en

FIG. 37. — Lacerta viridis. The chondrocraniuna from above (after
\V. 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 : e.n,
external nares : ep, epiotic : e.pt, epipterygoid : f./n, foramen magnum :
fo, fontanelle : /i.s.c, position of horizontal semicircular canal : i.o.s,
interorbital septum : na, nasal capsule : o.c, occipital condyle : p.oc,
parotic process : pr.o, prootic : p.s.c, position of posterior semicircular
canal : s. n, septum nasi : s.o, 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. 145

71. A cartilaginous process, the inferior turbinal, passes imrards
from, the anterior part of the lateral wall of the olfactory capsule,
and serves to increase the surface of the olfactory mucous membrane.

72. The septo-maxillary (Fig. 35, s.mx), 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 junction 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.

81. 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 (p.cd), 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).

83. 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.

IX. In the shoulder-girdle note

84. 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 scapulae, articulating each with the outer
extremity of the corresponding coracoid, and forming the
dorsal half of the glenoid cavity.

86. The suprascapulse, continuous with the expanded

THE LIZARD. *47

dorsal extremities of the scapulae, and passing inwards
towards the vertebral column : they expand gradually to the
dorsal edge, and consist, like the sternum, of partly calcined
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.

88. 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.

90. 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.

91. If the limb is extended at right 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

L 2

148 ZOOTOMV.

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 calcined 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 calcined 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 i : 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 plialanges.

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 (§ no).

I5o ZOOTOMV.

100. Each limb of the os innominatum is a separate
bone, 'the three meeting in the acetabulum in the tri-radiate
suture.

101. 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.

102. 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 of
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.

105. 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 cloacae, a small rod of bone passing horizontally back-
wards from the symphysis ischii in 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.

no. 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.

in. 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 ZOOTOMV.

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 fibre-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 of 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 :-

1 1 6. 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. §§ 89 — 97).

1 1 8. 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 ZOOTOMV.

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

-us)-

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 belo\v
the general level of the head, is the thin tympanic
membrane.

123. The vent, or cloacal aperture (Fig. 39, <-/), 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 ;

FIG. 38. — The head from above and from the side of — A. Lacerta
viridis ; B. Lacerta agilis ; C. Zootoca vivipara (slightly 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 ZOOTOMV.

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, gr^en on the sides, and white beneath.
Zootoca vivipara is olive above, \\ith a white-edtjed 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, r.r, r.l, r.i), 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 tendinese, into segments, the
longitudinal fibres of which are inserted into the anterior

o

edges of the median ventral scales.

The rectus abdominis consists of three portions : a ventral portion
(rectus ventralis, r.v) arising from the last sternal rib and inserted into
the ischium : an external portion (rectus lateralis, r.l) beginning as a
thin sheet of fibres between the skin and the pectoral muscle (§ 127)

THE LIZARD.

157

o.ex.

O.C32

m

sr

r.v

cr

r.i

FIG. 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 \vith the rectus lateralis (r./) and superficial layer of the ex-
ternal oblique (o. ex].

158 ZOOTOMY.

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 (txjiy), pectoral (/), and external oblique (o.ex) muscles are
removed, as well as the posterior part of the rectus ventralis (r.v) : by
the removal of the pectoral the left half of the sterum (st) is exposed.

In, biceps : cl, cloacal aperture : c.mn, cerato-mandibularis : d, del-
toid : e.i, external intercostal : m.hy, mylo-hyoid : mn, mandible :
o.ex, obliquus externus, superficial portion : o.ex', deep portion of
the same : o.hy, omo-hyoid : o.i, obliquus internus : /, pectoralis :
per, peritoneum : r.i, rectus internus : r.l, rectus lateralis : r.v, rectus
ventralis : s.c.m, sterno-cleido-mastoideus : s.hy, sterno-hyoideus : sr,
serratus : st, sternum : st', its posterior prolongations.

and joining the preceding portion at its insertion : and an internal and
posterior portion (rectus internus, r.i) 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 (o.ex, o.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).

It consists of two layers, a superficial one (o.ex) arising by slips from
the vertebral ribs, and with its fibres ending against the outer border of

' O O

the rectus lateralis, with which it becomes indistinguishable posteriorly ;
and a deep portion (o.ex') lying within (dorsal to) the pectoral, and
similarly related to the rectus ventralis.

127. The pectoralis (/), 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 (rn.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 an<^ Fig. 39).

130. The external intercostal muscles (<?./), 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 (<?./), 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 little 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, lr\ a large, brownish organ,
occupying about the middle third of the body cavity, and
imperfectly divided into right and left lobes.

i6o

ZOOTOMY.

a.co

m.co

r.au

s.cl.v

Lau

FIG. 40. — Lacerta viridis. A dissection from the ventral aspect,
showing the alimentary, circulatory, respiratory, and urinorjenital organs
(nat. size). The liver (/;-) 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 cleferentia, is removed, as also is the right corpus
adiposum.

a.co, anterior cornu of hyoid : az, azygos, or cardinal vein : bjiy,
bcdy of hyoid : c, caudal vein : c,ad, corpus adiposum : c.m, cceliaco-
mesenteric artery, the branches of which have no reference letters, to
avoid confusing the fgure, (see § 159) : ci£t caecum : cr, carotid artery :
d.ao, dorsal aorta : du, duodenum : e.j'u, external jugular vein : <?/,
epididymis : efg, epigastric vein :f.a, femoral artery :f.v, femoral vein :
g.b, gall-bladder: i.ju, internal jugular vein: il, ileum : i.m, inferior
merenteric arteries : k, kidney : l.ao, left aortic arch : I. an, left auricle :
Ig, lui gs : If, liver : m.co, middle cornu of hyoid : p. a, pulmonary
artery : pc, pericardium : p.co, posterior cornu of hyoid : pit, pancreas :
//, pelvic vein : pt.c, postcaval vein : pt.v, portal vein : p.v, pulmonary
vein: r, rectum : r.au, right auricle : r./i.a, right hepatic artery: sr,
sciatic vein : scl.a, su1 clavian artery : scl.v, subclavian vein : spl, spleen :
sf, i-tomach : s.z>, sinus venosus : th, thyroid gland : tr, trachea : is,
testis : v, ventricle.

135. The gall-bladder (g,b), 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 (du, //), forming several coils in the
posterior third of the ccelome.

137. The corpora adiposa (c.act), paired masses of fat,
of somewhat semi-lunar 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, r,au, l.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 (pt.c\ a large vessel, usually
gorged with blood, passing from the anterior border of the
liver forwards to the right side of the heart.1

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.c).

XVII. Dissect away the mylo-hyoid (m./iy) and under-
lying muscles (c.inu, o.hy, s.hy, &c.} until the
following structures are laid bare :

144. The trachea (tr), an annulated tube lying in the
middle ventral line of the throat.

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 :
sUt 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 Caroline, 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 (///), 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.c\
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 i.ju\ coming from the lateral region of the
head and bringing blood from the brain, &c. ; the external
Jugular (e.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 (sd.i^ 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

(§§ 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, st\ 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 (du] 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 (/•), dis-
tinguished by its greater diameter and by having its anterior
end produced on the left side into a small blind pouch or
caecum.

151. The pancreas (/«), 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 (spf), 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 (c.m\ 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 cceliac 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.

1 60. 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 (pt.r), 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 respectively.

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 (rji.a), a small vessel springing from
the dorsal aorta, and passing parallel to the veins mentioned in § 163
to the right lobe ol 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.

In the male: —

1 66. The testes (Figs. 40 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 (ep\ a whitish, elongated body
attached to the inner face of each testis, and extending
backwards into the pelvic cavity (see § 190).

1 66

ZOOTOMY

168. The mesorchium (Fig. 41, MS.O), a fold of peri-
toneum suspending each testis to the dorsal body-wall : a
similar fold (b.lg) supports the epididymis, and is attached
in front along the line of junction of the colourless and
pigmented regions of peritoneum (§ 133).

mso

FIG. 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.

bl, urinary bladder : b lg, fold of peritoneum supporting epididymis :
el1, anterior, and cl~, posterior, division of cloaca: ep, epididymis: k,
kidney : ms.o, mesorchium : /, copulatory organs, of which the right is
shown retracted (/>') and the left everted (p) : r.m, retractor muscle of latter :
r, ridge separating anterior and posterior divisions of cloaca : ret, rectum :
ret', its opening into the cloaca : /, testis : u.g, urinogenital papilla and
aperture : v.d, vas deferens.

THE LIZARD.

In tJie 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.

in so

» r

cl.

FIG. 42. — Lacerta viridis. The 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 : cl1, an'erior, and cl2, posterior, division of
cloaca: k, kidney : nts.o, mesoarium : od, left oviduct : od', its peritoneal
aperture : od", aperture of right oviduct into the cloaca : ov>, ovary:
nr, aperture of ureter.

1 68 ZOOTOMY.

170. The oviducts (od), 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 (rns.o), a fold of peritoneum sus-
pending each ovary to the dorsal body-wall.

172. The broad ligament (b.lg), 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).

Jn 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
J76. The cloaca (Fig. 41, cll,d'2) or posterior division
of the alimentary canal, passing insensibly into the rectum
in front, and opening behind by the vent.

177. The urinary bladder (£/), 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. 40 — 42, £), 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, //) have already been
seen (§ 138) attached to the edges of the corpora adiposa :
traced backwards, each is s^en 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 (r) ;
it lies along the ventral aspect of the caudal vertebrae and
brings back blood from the various tissues of the tail.

1 80. 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 (/?•) and sciatic (st) 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 directly continued into the postcaval, while

1 70 ZOOTOMY.

the left crosses over to the right side to join its fellow at
about the level of the origin of the coeliaco-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 (f.a), 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 rugae 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 valvulas conniventes, delicate longitudinal
ridges on the mucous membrane of the small intestine.

186. The ileo-caecal 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

1 88. The division of the cloaca by an incomplete ridge
of mucous membrane (Figs. 41 and 42, r) into two sections,
an anterior (dl) receiving the rectum and a posterior (d~)
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.d}, convoluted
tubes, continuous with the epididymes in front, and passing
backwards to the dorsal wall of the cloaca.

191. The urinogenital apertures (u.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 maybe 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, od"}
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 (od'}.

195. The apertures of the ureters (ur), 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

(§ 19')-

XXII. Lay open the pericardium and observe

197. The ventricle (Figs. 40 and 43, v\ a fleshy conical
structure, having its pointed apex directed backwards and
connected to the pericardium by a fine ligament.

198. The right (r.aii) and left (l.au) auricles, thin-

172

ZOOTOMY.

walled chambers, situated anterior to the ventricle, to the base
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, p.a], lying to the animal's left, and the
left aorta (Lao) to the right, are situated ventrally at their
origin, while the right aorta (r.ao) is dorsal to the other

l.ao

ptf:

FIG. 43. — Lacerta viridis. The heart, from the dorsal side (X 3).

cr, carotid artery : e.ju, external, and i.ju, internal jugular vein : l.ao,
left aorta : t.au, left auricle : p. a, pulmonary artery : pr.c, right, and
pr.c', left, precaval vein: pt.c, postcaval vein: p.v, pulmonary vein:
r.ao, right aorta : r.aut right auricle : s.au, sinu-auricular aperture : s.cl,
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 (j.r), 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

precaval (pr.c) passing directly backwards, the postcaval
(pt.c) directly forwards into it, while the left precaval (pr.c),
on reaching the neck, turns mediamvards 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 (fl.v), bringing the blood
from the lungs, and uniting into a short common trunk
which enters the left auricle on its dorsal wall.

r.ao

duo

FIG. 44. — Lacerta viridis. The aortic arches, supposed to le
removed close to thtir origin from the heart (nat. size).

cr, carotid artery : d.as, dorsal aorta : l.ao, left aortic arch : p.a, pul-
monary artery : r.ao, right aortic arch : s.cl, 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 oesophagus and to unite with one
another on the ventral face of the vertebral column to form
the dorsal aorta (d.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

i74 ZOOTOMY.

(ductiis Botalli] : shortly before this union the carotid artery
proper is given off and passes forwards to the head.

205. The subclavian arteries (s.cl), 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.ait), 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 and 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 aortas, 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

the left being ventral to that of the right : all three arterial
apertures 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

O

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,

j75 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 nares, 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 piginented sac (Jacobson's organ)
lying under the na^al 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 ai d 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, m.d], 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

A

m.o

v4

m.o

FIG. 45. — Lacerta viridis. The brain ; A, from above, with the
left cerebral hemisphere (cJi) and optic lobe (<?./) opened ; B, from
beneath; c,'from the left side ; D, in -longitudinal vertical section.

N

1 78 ZOOTOMY.

a.c, anterior commu sure: aq.s, aqueduct of Sylvius: cb, cerebellum :
c.c, crura cerebri : c.h, cerebral hemispheres : ch.p, choroid plexus : c.s,
corpus striatum : /./«, foramen of Monro : inf, infunclibulum : m.o,
medulla oblongata : o.c, optic chiasma : o.l, optic lobes : olf, olfactory
lobes : o.t, optic tracts : o.v, aperture between aqueduct of Sylvius
and optic ventricle : p.c, posterior commissure : pn, pineal body : pty,
pituitary body: z/.3, third ventricle: v.q, fourth ventricle:/ — XII,
cerebral nerves.

223. The cerebellum (cb), a small semicircular flap
covering the anterior part of the medulla oblongata on the
dorsal side.

224. The fourth ventricle (7'. 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.t),
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.c).

226. The cerebral hemispheres (c.h), 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 (olf) 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 (/«), 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 (pty), a rounded mass situated

THE LIZARD. 179

in 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 (o.c), an x-shaped body situated
immediately anterior to the infundibulum, and consisting
of the optic tracts (o.t), 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 (XI), arising from
the spinal cord, and passing forwards, receiving fibres as it goes, to the
medulla oblongata, 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

iSo ZOOTOMY.

XXVII. Carefully cut into the cerebral hemisphere and
optic lobe of one (say the left) side,1 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 (o.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 (c.s).

244. The choroid plexus (ch.p\ 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, f.m), 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 (aq.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.

1 If another specimen is to be dissected, this may be done on both
sides, and a longitudinal section (§ XXIX) made of the second brain.

THE LIZARD. 181

248. The third ventricle (r. 3), a narrow vertical slit
between the optic thalami, continuing forwards the aqueduct
of Sylvius : it communicates in front by the foramen of
Monro (//«), 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 (p.c), a similar trans-
verse band connecting the optic thalami at their junction
with the mid-brain.

XXIX. 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 liria.)

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 vertebrae (§ i) 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 vertebrae, the
latter to the sternum ; a longitudinal vertical sec-
tion should be made of the skull with a fine
fret-saw.

THE TIGEON. 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 vertebrae, forming the
skeleton of the neck, and the last two of them bearing well-
developed ribs, which do not unite with the sternum ; (b)
the four anterior thoracic vertebras, all united with one
another and bearing ribs which articulate with the sternum ;
(c) the compound sacrum, consisting of several vertebras
ankylosed together, and giving attachment to the pelvis ; of
these ankylosed vertebras 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 • (d) the free caudal vertebrae, 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; (b) the lower jaw or mandible ; and (<•) 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.

5. 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

1 84 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 vertebrae 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.

9. 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.

10. 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 vertebrae note :

1 6. 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.

1 8. The absence of free ribs in the remaining vertebras :
the apparent transverse process is, however, perforated by
an aperture, the vertebrarterial canal, for the passage of
the vertebral artery (Fig. 54, p. 232, vr), 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-

i86 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 division : a delicate ligamentous cord, the
ligamentum suspensorium, passes from centrum to centrum through
the aperture in the meniscus.

V. In the thoracic vertebrae 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 laminae.

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 (§§ 14,
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.

trj

FIG. 46. — Columba livia. The sacrum of a nestling (about fourteen
days old), viewed from beneath ( x 2).

On the left side (right of the figure) the first two caudal ribs (c.r) are
removed, so as to show the dorsal transverse processes (tr.p") : the sub-
sequently ossifying membrane which fills up the intervals between the
iransverse processes is also removed on the same side : the last thoracic
vertebra is not shown, not yet having united with the sacrum.

The cartilaginous parts are dotted.

c.i, ossified centrum of first, and c. 7, of seventh caudal vertebra :
c.r, first caudal rib: /.I, centrum of first, and /.3 of third lumbar
vertebra: s.i, centrum of first, and s. 3 of third sacral vertebra : trp,
transverse process of first lumbar, tr.p', of second sacral, and tr.p",
of first caudal vertebra.

VI. In the remaining vertebrae entering into the com-
position of the compound sacrum make out :
26. The two or three lumbar vertebrae (Fig. 46, /. i — -
/. 3), immediately succeeding the fifth thoracic : each has a
stout wide body, short strong transverse processes abutting

1 88 ZOOTOMY.

against the ilia (§ 107), rudimentary neural spine, and no
hypapophysis.

27. The three or four sacral vertebrae (s.i — ^.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 (V. i), 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 (c.r) — from its centrum, which also
abut against the ilia : a distinct passage is left between the
two processes.

29. The remaining ankylosed caudal vertebrae, 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 vertebrae, each having a short
centrum, a well-marked spine, and long, flat, outstanding
transverse processes : ^in the last two there is also 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 vertebrae : it forms the hinder termi-
nation of the vertebral column and supports the uropygium
(§ 121, p. 209).

THE PIGEON.

189

B

F.IG. 47. — Columba livia. The skull of a young bird (about six
\veeks 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 : b.o, basioccipital :
</, dentary : e.o, exoccipital : eu, aperture of Eustachian tube : f-tn,
foramen magnum : fr, frontal : i.o.s, in*erorbital septum : jit, jugal :
!c, lacrymal : Ib.s, lambdoidal suture : m.eth, mesethmoid : mx, maxilla :
mx.p, maxillo-palatine process : na, na' , no.", nasal : o.c, occipital
condyle : or fr, orbital plate of frontal : pa, parietal : pa.s, para-
sphenoid ://, palatine :p.mx, premaxilla : pt, pterygoid : qu, quadrate :
s.art, supra-angnlar : s.o, supraoccipital : sq, squamosal : ty, 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, f.m) 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 (b.o),
one dorsal, the supraoccipital (s.o), and a pair lateral,
the exoccipitals (e.o); the supraoccipital is bounded above
by the lambdoidal suture (Ib.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 (pa] and frontals
(fr) 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. 191

40. In the young bird the antero-ventral region of each
side of the brain-case is formed by a separate bone, the
squamosal (sq\ 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 (or.fr), an inturned portion of the latter
bone, and a lower and larger portion, forming a distinct
bone, the alisphenoid (al.s).

43. The interorbital septum (i.0.s.)t 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
(in.etJi), 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 fenestrse, 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
(n), for the transmission of the optic nerves from the brain
to the eyes.

48. The tympanic cavity ((y), 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 exoccipitai behind, and by the
basi temporal (§ 50), beneath.

49. The parasphenoid (pa.s), 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 is a 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 (eu) 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 diploe : 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
cranii is deeply concave from before backwards for the re-
ception of the medulla oblongata (Fig. 58, m.o) : 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, cJi) ; 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, #./); behind and
below these two hollows is the cerebellar fossa for the
cerebellum (Fig. 58, cb\ 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 fossae : 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

O

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 diploe ;
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 (ix, 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 (xn) ; 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 (gu\ 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.

6r. The columella (Fig. 48), a small and delicate rod
cf bone, having its expanded inner end fixed in the fenestra

s.st..

St .JtSP^^ ~~~^::: v:3 '^'^-^ C. St.

I. St.

FIG. 48. — Columba livia. The columella auris ( x 8).
The cartilaginous parts are dotted.

e.st, extra-stapedial : i.st, infra-stapedial : s.st, supra-stapedial : st,
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
§ 3J7> P- 250.)

The columella consists of a slender bony rod, having at its inner end
an oval plate of bone, the stapes (st), 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-stapedisl ; the second
division, situated dorsally, is the supra-stapedial (s.st) ; the third,
central in position, the infra-stapedial (i.st) ; the supra- is connected
with the extra-stapedial by an oblique bar of cartilage.

62. The pterygoids (Fig. 47, //), short, stout, paired
bones on the base of the skull, each articulating behind

o 2

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 (pi), 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
maxillae (§ 67).

64. The vomer, a small median bone, lying between the
palatines at the anterior end of the parasphenoid.

65. The lacrymal (lc), a considerable bone forming the
anterior wall of each orbit, and articulating above with the
corresponding frontal.

66. The premaxillae (pmx), 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 maxillae (MX), continuing backwards the max-
illary processes of the premaxillce, 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 (inxp), 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 (///), 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 (na), a long, forked bone, fitting against
the anterior edge of the frontal, and having a short external
process (na") which extends obliquely downwards and for-
wards to the maxilla, and a longer anterior process (na')
which passes forwards external and parallel to the nasal
process of the premaxilla.

71. The anterior nasal fossae, large vacuities one on
ach side of the beak, bounded above by the internal pro-
cesses of the nasals and nasal processes of the premaxillae,
below by the maxillae, 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
a 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

ig3 ZOOTOMY.

bones ; a stout irregular articular (ar), furnishing the
articular cavity for the quadrate, and continued forwards
into a slender Meckel's cartilage ; a splint-like bone, the
angular (an\ 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.

XL 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 fenestrae, 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, a small 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 fossae on the
anterior border of the body of the sternum, extending

200 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.1

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

90, 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.

91. 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.

"i

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 mantis the dorsal
surface looks upwards and the pre-axial border downwards
and forwards.

95. 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 ; 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.i) articulating with the radius, the larger (ulnare, cp.2)
with the ulna.

99. The metacarpus or middle division of the manus,
consisting of (a) a large cylindrical bone, the second m eta-
carpal (mcp. 2}; (b) a slender curved bone, the third
metacarpal (mcp. 3), on the post- axial side of the second,
to which it is ankylosed at its extremities, its shaft remaining

Ta

FIG. 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.

<r/.i, radial, and cf>.2., ulnar carpal : mcp. I, first, mcp. 2, second, and
mcp.i), third, metacarpal : ph. I, phalanx of pollex : ph. 2, proximal, and
p/i.2.', distal phalanx of second digit : ph. 3, phalanx of third digit : ra,
radius : ul, ulna.

free; (c) the first metacarpal (mcp.i), 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 (///. i), 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 (ph. 2] being flattened and very thin on its
post-axial side, the distal one (p/i.2J) pointed and concave
dorsally : the third metacarpal bears a single pointed
phalanx (ph. 3).

101. 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 :

102. It consists of two paired bones, the ossa inno-
minata (Fig. 50), more or less extensively ankylosed to

n

obf is

fu

FIG. 50. — Columba livia. Left os innominatum of a nestling
(fourteen days), viewed from without ( x 2).

The cartilage is distinguished by dotting.

ac, acetabuluin : a.tr, anti-trochanter : il, pre-, and z7, post-
acetabular portion of ilium : is, ischium : t.s.f, ilio-sciatic foramen :
ob.ft obturator fissure : pu, pubis.

the sacrum in the adult, but easily separable in the young
bird.

103. The acetabulum (Fig. 48, ac),& 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.tr).

THE PIGEON. 205

104. The ilio-sciatic foramen (f.s.f), a large aperture
immediately posterior to the acetabulum.

105. The pubis (/«), 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 (ob.f).

1 06. The ischium (is), 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 (//, //'), which consists of pre- and post-acetabular
portions, the former (it) ankylosed at the ventral boundary
of the acetabulum with the pubis, the latter (//') 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.

no. 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.

in. 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.

mtl2

FIG. 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 (tl.i, tl.2) are represented as separated from
the tibia and metatarsus respectively.

The cartilaginous parts are dotted.

m'.Z.2, second, mtl. 3, third, and mtl.^, fourth metatarsal : ti, tibia :
//.I, proximal tarsal cartilage, afterwards fusing with tibia : tl.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, //.i) : its separateness
in the cartilaginous state distinguishes it from an epiphysis,
which is a distinct ossification in a continuous cartilage.

238 ZOOTOMY.

115. The patella, a small nodule of bone in front of
the knee-joint, connected by ligament with the femur and
tibio-tarsus.

1 1 6. The fibula, a slender 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.

1 1 8. 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,
tl.2] and the remainder is formed of three separate long
bones, (metatarsals, mtl.2, mtL^ mil. 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.

1 20. 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
innermost 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

v

the bird, leaving the other side untouched, or
better, have two birds for comparison, one entire,
the other plucked : note the following external
characters :

121. 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 pennse 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.

125. 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

(§ 15°).

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 ij 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. 211

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 proximal stem, the tarso-metatarsus, and of
four digits, the first (pre-axial, § in) 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 form a number of
feather-tracts or pterylse, 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,

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

THE PIGEON. 213

anterior (dorsal) surface of the tarso-metatarsus and on the
dorsal surface of the toes.

XVII.1 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 2 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 du section of the soft parts is completed, and to
proceed from § 141 to Section XX., p. 214.

- 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 booklets, 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 booklets.

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

1 If it 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
tatter 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 oesophagus 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.

151. The trachea, a narrow tube, surrounded1 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 pectoralis 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.

1 58. The transversus 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
(§ I59) : 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 (§ 1 64) : 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 Irom 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.

2iS 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.

1 68. The pectoral arteries and veins, large vessels
distributed to the pectoral muscles, and, at present, pre-
venting further reflection of the pectoralis major.1

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 XXII., 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 ccelorne, 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 coelome, 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 vertebrae 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

222 ZOOTOMY.

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 of its 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.

o o

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 laminse, of which the right passes across the
duodenum and becomes attached to the posterior surface of
the right lobe of the liver, forming the duodeno-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).

1 86. 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 caeca, 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, \vhitish 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, c.m.r), 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 pDrtal 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 cceliac 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 coeliac 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 coeliac, 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-pulmonary 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 leaves it 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 PIGEOX. 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.

XL 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 midway 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-sacs from the kidneys
and reproductive organs, taking care not to
injure the postcaval vein (§ 215), and, in the

Q 2

22S

ZOOTOMY.

female, the anterior end of the oviduct (§ 212) :
make out :
In the male.

209. The testes (Fig. 52, ts\ two white, ovoidal bodies,
about three-quarters of an inch long in the adult, but very

V.s

V.d

FIG. 52. — Columba livia. The urinogenital organs of an adult
male, ventral aspect ( x |).

The right testis and vas deferens are separated from the kidney and
ureter, and displaced outwards.

adr, adrenal : cl.2, middle, and ^/.3, posterior, compartment of cloaca :
k, kidney : ts, testis : ur, ureter : uij, opening of ureter into cloaca :
v.d, vas deferens : v.d1 ', its opening 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
irom the inner face of each testis, and passing directly

THE PIGEON. 229

backwards to the cloaca (V/), where it ends in a dilatation,
the vesicula seminalis (v.s) (see § 231, p. 236).
In 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 (l.od), 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
(l.od"\ 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
(l.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 (r.od), 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.

In both sexes.

214. The kidneys (Figs. 52 and 53, k), 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 —

230 ZOOTOMY.

which are embedded in cavities furnished by the pelvis and
sacrum.

215. The postcaval vein (vena cava inferior s.
posterior,) (Fig. 54,/fc), 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

ur

T.od

l.od"

l.od/

FIG. 53. — Columba livia. The urinogenital organs of an adult
female, ventral aspect ( x f ).

The peritoneum is removed, but the parts are in situ, except that the
left oviduct is partly uncoiled.

cl.2, middle, and cl.^, posterior, compartment of cloaca : /', kidney ;
Lod^ left oviduct: l.od', its opening into cloaca: Lod", its funnel-like
anterior end : l.od'", its opening into crelorne : ov, ovary ; r.od, rudi-
mentary right oviduct : r.od', its opening into cloaca : ur, ureter : ur',
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, ur), 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
lie careful not to injure the renal (§ 220) or the hypogastric
(§ 218) vein.

217. The adrenals or supra-renal bodies (Fig. 52,
iidr\ 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, r.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 (c.m.r} : 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 (/.//) from
the roof of the pelvis.

r.prc
r.au

sc.a

FIG. 54. — Columba livia. The blood vascular system, from the
ventral aspect (nat. size).

THE TIGEON. 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 th^ heart and the
coccygeo-rnesenteric vein (p.m.v) are displaced to the left.

a.ao, arch of the aorta: a.in.a, anterior inesenteric artery: a.r,v,
afferent renal veins : a.r.v, vein bringing blood from pelvis into renal
portal system : br.a, brachial artery : br.v, brachial vein : c, caudal
artery and vein : c.c. common carotid artery : c.m.v, coccygeo-mesen-
teric vein : cce.a, cceliac artery : d.ao, dorsal aorta : e.c, external carotid
artery : epg, epigastric vein : c.r.z*, efferent renal veins : f.a, femoral
artery :f.v, femoral vein : h.v, hepatic vein : i.c, internal carotid artery :
/.zY, internal iliac artery and vein : i.m, internal mammary artery and
vein : in. a, innominate artery : i.v, iliac vein : jit, jugular vein : ju',
anastomosis of jugular veins : l.au, left auricle : I p. a, left pulmonary
artery : l.prc, left precaval vein : l.vn, left ventricle : pc, lefc pectoral
arteries and veins : pc.a, right pectoral artery : pc.v, right pectoral vein :
p. m.a, posterior inesenteric artery : ptc, p^stcaval vein : r.a.i, anterior,
r.a.2, middle, and r.a.^, posterior, renal artery : r.au, right auricle :
r.p, renal portal vein : r.p.a, right pulmonary artery: r.prc, right pre-
caval vein ; r.v, renal vein : r.rn, right ventricle : sc.a, sciatic artery :
sc.v, sciatic vein : set. a, subclavian artery : vr, vertebral artery and
vein.

219. The femoral vein (f.v), a large trunk returning
the greater part of the blood frorn the leg,1 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 (r.i<\ 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 (e.r.v) from the
middle and posterior lobe of the kidney : the blood from the anterior
iobe 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 passu 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 (r.p], 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.r.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
small veins from the sacral region (a.r.v').

223. The femoral artery (/.a), 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 (sc.a), 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 (st.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 (r.a. i), 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 (r.a. 3),
arising from the sciatic a little external to the last, and passing backwards
to the posterior lobe.

220. The origin of the cceliac (cce.a) and anterior
mesenteric arteries (a.m.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 (d.\) is almost globular when
distended, and receives the rectum ; the middle chamber
(d.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 (cl.$) 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 (ur)
in the dorsal wall of the middle chamber.

236

ZOOTOMY.

231. In the male the genital papillae (Fig. 52, v.d')
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, l.od'}, a considerable opening just external to that
of the left ureter : the rudimentary right oviduct has a

FIG. 55. — Columba livia. The cloaca of a young female. A, opened
fro 01 the ventral aspect ; B, in longitudinal section (nat. size).

b.f, bursa Fabricii : b.f, its opening into posterior chamber of cloaca :
r/.i, anterior, cl.2, middle, and cl.?,, posterior, chamber of cloaca : od,
opening of oviducts into middle chamber of cloaca : r, rectum : w,
opening of ureters into middle chamber of cloaca.

small opening (r.od'} similarly situated on the right side :
in the young bird the two apertures are of equal size
(Fig. 55, od).

233. The aperture of the bursa Fabricii (Fig. 55, &/'), 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 (b.f), 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, Lvn\ 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.vn\ much softer to the
touch than the left, and forming the right concave side of
the ventricular division.

237. The right auricle (r.au)9foimmg the right half of the
auricular division, and usually gorged with blood after death.

238. The left auricle (l.au), usually in a more collapsed
state than the right.

239. The innominate arteries (in. 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.c), which proceeds almost
directly forwards, and the subclavian (scl.a}, which con-
tinues the direction of the innominate, and almost immediately
divides into two : of these the brachial or axillary artery
(br.d) passes forwards and outwards, and curving round
at the shoulder enters the wing, which it supplies,1 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 (pc.ci) continues the direction of the
innominate and subclavian, which it nearly equals in calibre,
and supplies the pectoral muscles.

240. The internal mammary artery (/.;«.), a small vessel given off
from the posterior surface of the subclavian : it passes backwards along
the inner surface of the ribband 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 (l.p.a)
passes forwards and outwards, parallel to the left innominate,
while the other (r.p.a) turns to the right and passes to the
dorsal side of the innominates.

243. The right precaval veins (vena cava superior s.
anterior dextra,) (r.prc}, a large vessel situated dorsal and
external to the right innominate artery : it is formed by the
union of three veins, the jugular (jii) (§ 249) from the
neck, the brachial (br.v) from the wing, and the pectoral
(pc.v) from the pectoral muscles : posteriorly it enters the
right auricle at its anterior end.

244. The internal mammary vein (i.m), 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. 239

245. The left precaval vein (vena cava superior s.
anterior sinistra), (l.prc), 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, ^here its further course will be seen subsequently

(§ 254).

246. The postcaval vein (ptc) 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
(c.c\ 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 vertebras : about an inch behind the head, the
arteries diverge again, and each, passing forwards and
slightly outwards, divides into an external carotid (e.c),
supplying the head generally, and an internal carotid
(t.f), supplying the brain.

248. The vertebral artery (vr\ 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 (J2t) : they are
united with one another by a transverse commissure (jit] 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 palaLe, 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.

XXXVII. 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 (h.v), of which the latter is
the larger, entering the postcaval just before its exit from the liver.

253. The epigastric vein (epg) (§ 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. ^b.l.prc] curving round the
dorsal side of the left auricle to reach the right auricle.

255. The pulmonary veins (p.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 (r.p.a, l.p.a) (§ 242) to the lungs.

257. The arch of the aorta (a.ao) (§ 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.

a.ao

FIG. 56.— Columba livia. The heart, viewed from the dorsal
aspect (nat. size).

a.ao, arch of aorta: br.a, brachial artery: br.v, brachial vein : c.c,
common carotid ; ju, jugular ; l.au, left auricle: l.p.a, left pulmonary
artery : l.prc, left precaval : l.vn, left ventricle : r.au, right auricle :
r.au', its smooth-walled dorsal portion receiving the pre- and post-
cavals : r.p.a, right pulmonary artery : r.prc, right precaval : r.vn,
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 (§ 269).

XLI. Open the right ventricle by a V-shaped incision,
introducing the scissors into the cut end of the*
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 columnae carneae, 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 chordae tendineae,
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
(§ J59) 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 aperture of 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.

sl.l

FIG. 57.— Columba livia. The lung?, filled from the trachea with
a solid injection and viewed from the ventral aspect (nat. size).

In the left lung the bronchus (/;;-, br'} is traced to its termination by
dissecting away the overlying substance of the lung.

br, principal bronchus : br1, br", br'", secondary bronchi : p. a,
pulmonary artery : p. v, pulmonary vein : sy, syrinx : tr, trachea : sp. b,
aperture for prebronchial air-sac: sb.b, for sub-bronchial: a. in, for
anterior-intermediate : p. in, for posterior-intermediate : /, for posterior
(abdominal).

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 (br', br", br'") 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 (j>) is at the postero-external angle of the lung : that of the
posterior-intermediate (p. in) just anterior and external to the last : that
of the anterior-intermediate (a. in) 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 (sb.b) is also on the
ventral surface, just anterior to the entrance of the chief bronchus : and
that of the prebronchial (sp.b) 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), it is 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 (p.in), the posterior with the posterior sac (ab) : 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.

o o

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 vertebrae, and passing
transversely outwards parallel to and equidistant from the
ribs.

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
vertebrae : 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 vertebrae :
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
irnpar : 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.

XLVI I. 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 : (b) 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, §§ 191 — 203) : 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
a concave 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 cf the

250 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 flat 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.

LII. 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).

LIII. Carefully remove the skin from the shoulder and
wing, and dissect oft' 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-arrn.

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 (§ 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 flexores 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 bifurcations 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, a 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, m.o\ con-
tinuous behind with the spinal cord, and like it composed
externally of white matter : l it greatly exceeds the cord in

1 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.

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.^).

A

B

cJi

O.I

FIG. 58. — Columba livia. The brain. A, from above ; B, from
beneath ; C, from the left side ( x 2).

cb, cerebellum : c.h, cerebral hemispheres : f, flocculus : inf, infun-
dibulum : m.o, medulla oblongata : o.l, optic lobes : olf, olfactory lobes :
o.t, optic tracts : pn, pineal body : H-XII, roots of cerebral nerves :
sp.lt root of first spinal nerve.

256 ZOOTOMY.

339. The cerebellum (Fig. 58, cb\ 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 (<?./), paired, white, ovoidal bodies,
situated one on either side, immediately in front of the
medulla and below the cerebellum.

341. The cerebral hemispheres (c.h\ 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 (pn\ a small rounded mass on
the dorsal surface of the brain, wedged in between the
cerebral hemispheres and the cerebellum.

343. The olfactory lobes (olf\ 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 (o.t\ 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 (u) spring.

345. The infundibulum (/«/), 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 (in), 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 (iv), 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 (vn), a small trunk arising
close behind the fifth.

351. The eighth or auditory nerve (vin), a large, soft
trunk arising close behind the seventh : its fibres are traceable
upwards to the dorsal pyramids of the medulla.

352. The ninth (ix), 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 (xn), 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
(§ 35 7) : 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, p) : from its attachments the cerebellum extends
backwards over the medulla and forwards between the
optic lobes.

355. The optic commissure (o.c\ a flat, horizontal
band .of white fibres uniting the optic lobes beneath the
anterior prolongation of the cerebellum.

356. The thalamencephalon (the), 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 of 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 (?'.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, (/./").

c.h

a/.c

o.c

7n.r.

FIG. 59. — 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 : c.h, cerebral hemispheres :
c.s, corpus striatum : f.m, foramen of Monro : inf, infundibulum : m.o,
medulla oblongata : o.c, optic commissure: o.ch, optic chiasma : o.l,
optic lobes : olf, olfactory lobes : o.v, optic ventricle : p. peduncles of
cerebellum : p.c, posterior commissure : pn, pineal body: th-c, thala-
mencephalon : ^.3, third ventricle : £-.4, fourth ventricle.

S 2

260 ZOOTOMY.

3;

159. The foramen of Monro (/;;*), 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 (p.c\ a similar cord
uniting the thalami immediately in front of the optic
commissure.

362. The fourth ventricle (v.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, <?.?;), a cavity in
each optic lober 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, ^.3, v. 4).

366. The relation of the foramen of Monro (f.m) 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 (/>{/").

THE PIGEON. 261

3'

[68. The relations of the anterior (a.c\ posterior (j>.c),
and optic (o.c] commissures.

369. The arbor vitae, 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. If a second brain is not at hand, this maybe seen
in a section of the cerebellum removed in § LVI : it is best
seen, however, in a fresh brain.

THE RABBIT (Lepus cuniculns}.

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 vertebras
which immediately follow the head ; the thoracic region,

THE RABBIT. 263

consisting of twelve or sometimes thirteen rib-bearing ver-
tebrae ; the lumbar region, containing seven or some-
times six large vertebrae without ribs; the sacral region,
consisting of four vertebrae more or less completely fused
into a 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 small 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, divisible 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 vertebrae
note :

9. The centrum or body, a sub-trihedral mass of bone
forming the ventral portion of the vertebra.

10. 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 laminae.

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.1

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.

1 6. 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 serve's 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 vertebrae : 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 vertebrae : 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 vertebrae: these are much like the,

*

lumbar, but have smaller metapophyses, and no anapo-
physes or hypapophyses. In the first the spine is usually
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 vertebrae, 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 vertebrae : these
have the centrum with its 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 belo\v
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 vertebrae : 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 sternebrse, 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.

40. 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.

4?. 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 laminae, 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 laminae, 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 wing-like laminae
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 ZOOTOMV.

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

T

274 ZOOTOMY.

front to the septum and free behind, and are ensheathed in
the palatine processes of the preinaxillre. 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.

6 1. 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-turbmal.

64. The premaxillse, 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 maxillae, two large and very irregular bones,
which, together with the premaxillse, form the framework of
the upper jaw. Their outer surfaces are spongy ; on their

THE RABBIT. 275

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 laminae of bone, which articulate
in front with the maxillae, 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 proc ss, 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

T 2

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 fossse for the reception of the chief divisions of
the brain. The hindmost of these, or cerebellar fossa,
for the lodgment of the cerebellum (§ 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).

Interposed 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 : l

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 cms.

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 dissectioa. See Sees. 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.

IX. In the shoulder-girdle and fore-limb note :

8 1. 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. 279

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 presents 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 wall be seen that the altered position of
the parts in the mammal is due to the following changes : l
(i) 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.

2So 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). In the 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 i), 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,

cS2 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.

90. The sesamoid bones, small nodular ossicles situated on the
palmar side of the joints of the dibits : 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 :
91. 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,1 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).

92. If the hind-limb be compared with that of the Lizard
(p. 151 § 1 08), it will be seen that the femur, and with it
the whole limb, has undergone rotation forwards : as a con-
sequence of this the hind-limb 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.

284 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 fabellse, 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.

99. 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 i), 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,

2S6 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.

1 01. 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.

104. 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.

1 06. 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 vibrissae, or "whiskers," a number of long
stout bristles on the upper lip.

THE RABBIT. 287

109. 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.

1 10. The auditory apertures, one on either side of the
hinder region of the head, guarded by the large external
ears.

in. 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.

114. 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.

1 1 6. Theurinogenital 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.

1 1 8. 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, i.e., 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 rings ;
it ends in front in the larynx, which is situated in the binder
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 fibresof the pectoralis major pass either directly outwards, 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 § 401).

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 : irs 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 perito-
neuni (§ 145), 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 leer.

O

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.

u 2

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 caecum 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
caecum, with which it is seen to be connected, and which it
resembles in colour ; its diameter is less than that of the
caecum, 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 fecal matter.

J53- 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 (i.e. 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, a dark-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 pink 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 trachea, by making a small
aperture in it and inserting a blowpipe.

1 6 1. 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).

XV. Place the animal in the prone position, i.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 vertebrae,

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. As in 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 by a
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, r.c), and the dorsal caudate lobe (can) closely
applied to the right kidney ; and on the left side, the
ventral left central lobe (l.c), the dorsal left lateral
lobe (/./) fitting against the left anterior region of the
stomach, and the small Spigelian lobe (spg\ fitting closely
into the lesser curvature (see § 168) of the stomach.

1 66. The gall bladder, a green pyriform sac, embedded
in the right central lobe of the liver.

167. The oesophagus, or gullet, a narrow tube emerg-
ing from the thorax through an aperture in the diaphragm,
dorsal to the liver, and entering the stomach.

1 68. 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 oeso-
phagus towards the left of the lesser curvature, and the

THE RABBIT. 297

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, n 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 by a 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 caecum 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 csecum, 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 caecum, and the exit of the colon from the same.

177. The termination of the distal or blind extremity of
the caecum 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 :
T8o. The postcaval vein, or inferior vena cava 1

1 A rabbit is best 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 frooi 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. 299

(Fig. 6i,/fr), 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 cceliac artery (cat. 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 cceliac 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).

1 86. The gastric branch of the vagus, a small nerve taking a
somewhat spiral course round 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, can.),
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 caunula, 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).

1 88. 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.

190. 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 (p.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.v\
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 (pn), 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 (pn.d), a short delicate tube,

1.1

II

h.

sp.a,

FIG. 60. — Lepus cuniculus. The stomach, duodenum, pos-
terior portion of rectum, and liver (in outline), with their arteries, veins,
and ducts. A. The coeliac artery of another specimen (both X |).

302 ZOOTOMY.

The gullet (ces) is cut through and the stomach somewhat displaced
backwards to show the ramifications of the coeliac artery (ca'.a) : the
duodenum (Jit) is spread out to the right of the subject to show the
pancreas (pn) : the branches of the bile-duct (c.b.d), portal vein (p.v),
and hepatic artery (h.a), are supposed to be traced a short distance into
the various lobes of the liver.

a.m. a, anterior mcsenteric artery : cau, caudate lobe of liver, with
its artery, vein, and bile-duct : c.b.d, common bile-duct : cd.sl, cardiac
portion of stomach : c.il.a, common iliac artery: cce.a, cceliac artery :
ty.a, cystic artery : cy.d, cystic duct : d.ao, dorsal aorta : du, proximal,
and dit', distal, limbs of duodenum : dit.a, duodenal artery : du.k.a
(in A), duodeno-hepatic artery : g.a, gastric artery and vein : g.b, gall
bladder : h.a, hepatic artery : h.d, left bile-duct : l.c, left central lobe of
liver, with its artery, vein, and bile-duct : l.g.v, lieno -gastric vein :
/./, left lateral lobe of liver, with its artery, vein, and bile-duct: ms,
branch of mesenteric artery and vein to duodenum : ms.r, mesorectum :
m.v, chief mesenteric vein : as, oesophagus -.p.m. a, posterior mesenteric
artery: p.m.v, posterior mesenteric vein : pn, pancreas • pn.d, pan-
creatic duct : p.v, portal vein : py.st, pyloric portion of stomach : ret,
rectum : r.c, right central lobe of liver, with its artery, vein, and bile-
duct : j/.if, Spigelian lobe of liver, with its artery, vein, and bile-
duct : spl, spleen : sp.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 (c.b.d\ 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 various 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 a right bile-duct : the left central and left lateral
ducts similarly unite to form a left bile-duct (h.d] : the right and
left bile-ducts unite to form the common bile-duct (c.b.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 cceliac artery (§ 182) : shortly after its origin
from the aorta it sends off to the left the splenic artery (sp.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 coeliac, is the hepatic artery (h.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.d) to the gall bladder : coining off to the right of the hepatic
is the duodenal artery (du.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 (^.r), 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, m.v) towards the animal's right side, and the
lieno-gastric vein (l.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.

201. The lacteals, delicate, transparent, colourless vessels
in the mesentery, running more or less parallel to the
arteries and veins.

XXL 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 caecum : the cascum 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 cobn occur in three longitudinal rows,
separated by three muscular bands, or taeniae 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 caecum with a small portion of the ileum
and colon, clear out its contents bv directing: a stream of water

** o

through it, and either distend with air and dry, or, better,
distend with a o'5 per cent solution of chromic acid and place
in a vessel of the same fluid 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 rugae 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.

2JO. The irregular transverse ridges orvalvulae 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 hand 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 vermiform is 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 of the colon, the smooth character of that of
the rectum.

XXIII. 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 vertebne.

217. The aorta, passing from the abdominal cavity for-
wards between the pillars of the diaphragm.

218. The oesophagus, 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, h.v), by which
the blood is taken from the liver to the postcaval : they are
best seen by slitting up the infra-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 (i.pJi) 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 pleurae : 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)
mediastinai 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.
a.t 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.

x 2

3o8 ZOOTOMV.

XXVI. Dissect away the pericardium, the thymus 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, /.?-), 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 (r.r), 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 auricles (r.aii, Lau], 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 (/.#), proceeding from the
cone-like 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 (p.v\ returning the blood
from the lung to the left auricle. They are best seen at a
later stage (see § 306).

e.c

FIG. 61.— Lepus cuniculus. The vascular system (X

3io ZOOTOMV.

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 : a.epg, internal mammary artery : a.f, anterior
facial vein : a.m, anterior niesenteric artery : a.ph, anterior phrenic
vein : az.v, azygos vein : br, brachial artery : cM.a, common iliac
artery : c.il.v, common iliac vein : c&, coeliac artery : d.ao, dorsal
aorfa : e.c, external carotid artery: .e.il.a, external iliac artery: e.il.v,
external iliac vein : e.jti, external jugular vein : Jin. a, femoral artery :
fm.v, femoral vein : h.v, hepatic veins : i.c, internal carotid artery : i.cs,
intercostal vessels: i.il.a, internal iliac artery: i.il.v, internal iliac
vein : i.ju, internal jugular vein : i.l, ilio-lumbar artery and vein : in,
innominate artery : l.au, left auricle : L-'.L, left common carotid artery :
l.prc, left precaval vein : /. z/, left ventricle : in.sc, median sacral artery :
p. a, pulmonary artery: p.epg, epigastric artery and vein : p.f, posterior
facial vein : p. in, posterior mesenteric artery : p.ph, posterior phrenic
veins : ptc, postcaval vein : p.v, pulmonary vein: r, renal artery and
vein : r.au, right auricle : r.c.c, right common carotid artery : r.prc,
right precaval vein : r. z>, right ventricle : scl.a, subclavian artery : scl.v,
subclavian vein : spin, spermatic artery and vein : s.vs, superior vesical
artery and vein : ut, uterine artery and vein : vr, vertebral artery.

231. The two precaval veins, or venae cavse supe-
riores (r.prc, l.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 (scl.v), from the
corresponding arm, and the external jugular vein
(e.jii) already noticed (§ 127) from the head ; the right pre-
caval is seen at once to enter the right 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, (/./), coining from the external ear ; near its junc-
tion with the subclavian, it receives the internal jugular vein (i.jtt),
which runs close alongside the trachea, and receives the blood from the
brain.

THE RABBIT. 311

232. The thoracic portion of the postcaval vein (ptc],
passing forwards from the diaphragm to the right auricle.

233. The anterior phrenic vein (a.ph), passing forwards from the
diaphragm, alongside the postcaval, and pouring its contents into the
right precaval.

234. The oesophagus, 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 (<?<?), 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.ao), 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 last into the two common iliac arteries

312 ZOOTOMV.

(c.il.a, § 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 (i.cs) 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 (/;/), springing from the
arch of the aorta towards its right side ; it gives off at its
origin the left common carotid artery (l.c.cj and then,
passing forward, divides into the right common carotid
(r.c.c] and right subclavian (s.cl.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 oi"
the larynx, divides into the internal carotid (/.<-), which
passes dorsalwards to reach the brain, and the external
carotid (e.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 backward-, the right vagus is seen to pass across (ventral to)
the ri^ht 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 is a flat pale
nerve lying immediately dor.-ai to the artery : traced backwards, it
enlarges at about the level of the first ril> 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 immediately
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
(&r), which passes directly outwards, and sends branches
to the fore-limb and shoulder-girdle, giving off also the
internal mammary artery (a.epg), 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 (;-), 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 (r\ 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 (spm\ 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.st), a small trunk arising from

THE RABBIT. 315

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 (cM.a), formed by
the bifurcation of the aorta : each gives off soon after its
origin the iiio-lumbar artery (/./) to the posterior part
of the dorsal abdominal walls, and then almost immediately
divides into the internal iliac (til. a), which passes along
the dorsal wall of the pelvic cavity, and the external iliac
(e.il.a), which gives off an artery to the bladder and uterus,
and then, passing beneath Poupart's ligament, becomes the
femoral artery (/;;/.#), and supplies the leg. Immediately
external to Poupart's ligament the femoral gives off the
posterior epigastric artery (p.epg), which is distributed
to the ventral abdominal walls.

259. The ilio-lumbar veins (/./), large vessels which
enter the postcaval just anterior to the bifurcation of the
aorta.

In some cases the left ilio-luinbar 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. Tne trifurcation of the inferior cava at its posterior
end into the two outwardly directed external iliac veins
(e.il.V), and the median, backwardly directed common iliac
vein (c.ti.v). The external iliacs, like the corresponding
arteries to which they are parallel, are the intra-abdommal
portions of the femoral veins (/;;/.#), by which the blood
is returned from the legs ; they also receive the blood from
the bladder and uterus : the posterior epigastric veins
(P- ePS)-> open into the femorals immediately external to
Poupart's ligament. The common iliac is formed by the
union of the two internal iliac veins (i.il.v}, which run

316 ZOOTOMV.

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 nr) 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
line, and then backwards almost parallel with one another,
and enter

263. The bladder (bl), 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 from 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.

In the Male.

265. The penis (A, c.c, c.s, g.p), 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

ur

va.

II

u.g.a-

qcL an

J u.fj.a.

FIG. 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 lubes, and uteri, are not shown.

an, anus: bl, urinary bladder: c.c, corpus cavernosuin : c.s, corpus
spongiosum : c.gl, Cowper's gland : g.cl, glans clitoridis : g.p, glans
penis : p-gl, perineal gland : p.gl', aperture of its duct on the perineal
space : pr, anterior, pr1, posterior, and pr", lateral, lobes of prostate :
rcty rectum : r.gl, rectal gland : «.£".rt, urinogenital aperture : u.m,
uterus masculinus : ur, ureter : va, vagina : vb, vestibule : v.d, vas
deferens.

ventrally by the two hard, closely applied corpora
cavernosa (c.c), 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 (e.s, 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 (ii.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.a), 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 (//.;#), 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 (//'), a glandular mass, in relation with
the neck of the bladder and the uterus masculinus.

It consists of five lobes : an anterior (pr), so closely applied to the
dorsal wall of the uterus masculinus as to be almost inseparable from
it : another posterior (/>''), more prominent than the first, bilobed
anteriorly, and easily separable from the uterus masculinus; and two

326 ZOOTOMY.

small lateral lobes (pr"), lying along the sides of the neck of the
bladder.

275. Cowper's glands (c.gl], a pair of brown, ovoid masses, imme-
diately behind the posterior lobe of the prostate, and enclosed in a
layer of muscle.

276. The rectal glands (r.gl), 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 (/.£/), 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 (/.£"/').

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 coroora cavernosa : continue the

i.

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 verumontanurn.

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.

/// the Female.

285. The vulva, or external urinogenital aperture,
(Fig. 62, B, u.g.a) 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 (c.c, g.d), 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.cl), 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, r.ut, /.»/), paired tubes proceed-
ing from the anterior end of the vagina, and proceeding
outwards towards the flanks ; they are comparatively wide

Y

322

ZOOTOMY.

at their posterior or vaginal ends, but become narrow
anteriorly and pass almost insensibly into

289. The Fallopian tubes (//./), 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.

r.ut

FIG. 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.

Jl.t, Fallopian tube : _/?./', its peritoneal aperture : l.itt, left uterus :
l.ut', left os uteri : r.ut, right uterus : r.ui', right os uteri: 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, rb), 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.gl), 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 rugae 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, r.ut'\ 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 layer and an inner mucous layer raised up
into very large and prominent rugae.

301. The smooth walls of the Fallopian tube and the
opening of that tube posteriorly into the uterus, and
anteriorly by its funnel-like fimbriated extremity (fl.t'}
into the peritoneal cavity in the immediate neighbourhood
of the ovary.

/;/ 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 striae
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 venae cavae. 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 cavae 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 auriculae, 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 is a 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 columnse carnese, 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 chordae tendineae, 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 the 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 slightly 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.1 Remove both eyes : divide one of them into an
inner and an outer hemisphere by an equatorial
incision, i.e. 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,

1 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, §§ 224 — 228).

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) in situ, they
should be removed, and examined under a low power of the
microscope.

350. The fenestra ovaiis and fenestra rotunda

(§ 56)-

351. Tne aperture of the Eustachian tube on the

inner wall of the tympanum, below and anterior to the
fenestra ovaiis (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 (vl.pa).

360. The tongue (tg), firmly fixed by its postero-inferior
part to the floor of the mouth, presenting on its dorsal
surface a number of small elevations or papillae, 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 (epg),
and behind by two small processes of mucous membrane,
the cornicula laryngis (c.la).

363. The aperture of the posterior nares (p.na\ 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—8o, pp. 277, 278).

THE RABBIT. 335

The section is taken slightly to the left of the median plane so as to
clear the mesethmoid (m.etfi) : all but the anterior and posterior ends of
the septum nasi (m.et/r) is cut away, so as to expose the ri^ht nasal cavity
with its turbinals : the brain is removed, so as to show the cranial fossce
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.gl). The cartilage is distinguished
by fine, the bone by coarse, dotting.

b.hy, body of hyoid bone : b.o, basi-occipital : b.s, basi-sphenoid :
cb.fo, cerebral fossa : cbl.fo, cerebellar fossa : c.la, corniculum laryngis
embedding arytenoid cartilage : cr, cricoid cartilage :c.t.m, crico-thyroid
membrane : epg, epiglottis : eth.lb, ethmo-turbinal : eu, aperture of
Eustachian tube : fl.fo, floccular fossa :_/)-, frontal: f.v.c, false vocal
cord: g.hy, genio-hyoid muscle: i.e. a, internal carotid artery.: i.pa,
interparietal : ja, Jacobson's cartilage : Li, lower incisor : m, masseter
muscle covering edge cf mandible : m.etk''-, lamina perpendicularis :
m.etli1, septum nasi : inn, mandibular symphysis : mo, mouth cavity :
tnx, palatine plate of maxilla: mx.tb, maxillo-turbinal : na, nasal:
na.tb, naso-tiirbinal : oc.al.m, occipito-atlantal membrane : od, odontoid
process : as, oesophagus : ol.fo, olfactory fossa : pa, parietal : //, palatine
plate of palatine : pmx, premaxilla : p.na, posterior nares : p.s, pre-
sphenoid : s.^, sublingual gland : s.mx, subuiaxillary gland : s.o,
supra occipital: sp.i, sp.2, J/-3, roots of first three spinal nerves:
st.hy, sterno-hyoid muscle: s.t, sella turcica : tg, tongue: M, thyroid
cartilage : tn, tentorium : /;-, trachea : z/.z'1, anterior, and u.i-, posterior,
upper inci-or : v. I, atlas; v.2, centrum, and v.21, arch of axis:
y'3> v-3'> °f third vertebra : v.c, vocal cords : v.l, ventricles of larynx :
rl.pa, velum palati : vr.a, vertebral artery : x, bristle passed through
right nostril : y, bristle passed through right naso-Dalatine canal :
// — X//, roots of cerebral nerves.

365. The small paired aperture of the naso-palatine or
Stenson's canals (y), situated immediately behind the
posterior upper incisors (u.i2), 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.tb, 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.

XLVI1. 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 (eu), 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 (m.et/i1, § 59), forming a median
vertical partition between the anterior part of the two nasal
chambers.

372. Jacobson's cartilage (ja, § 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.

XLVIII. 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, M), a large plate of cartilage, consisting
of right and left alae united to one another ventrally at an obtuse
angle : dorsally each alse is produced into anterior and posterior
cornua, small processes, the posterior of which articulates with a facet
on the cricoid.

375. The cricoid (cr), 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
(cr.th.ni).

The anterior rinof of the trachea is often more or less transitional

•j

between the ordinary tracheal rings and the eric jid.

376. The arytenoids (ary\y 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 (c.la).

378. The epiglottis (epsf), 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.

o ^

379. The reddish mucous membrane lining the Jarynx, continuous
behind with that of the trachea and in front \viih that of the pharynx.

380. The ventricles of the larynx (:'./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 (f.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
parsing 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 arytenoicls : to see
them one of the alae 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,1 and
giving off nerves to the arm and shoulder.

Besides several smaller nerves there are four chief trunics given
off from the brachial plexus : 2 (a) the ulnar nerve runs alongside the
brachial artery, passes im nediately internal to the olecranon into the
fore-arm, and then aljng the outer or ulnar side of the latter : (b) the
median nerve 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 mainly 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 : (cf) 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 vertebras behind which they emerge : the first thoracic,
for instance, is the nerve which makes its exit between the first and
second thoracic vertebrae.

; 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 : (b) 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.1

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, /s), a thin superficial
sheet of muscle expending 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 fasciae : 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 (l.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 If 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.

Z 2

340

ZOOTOMY.

7.sc.m pcmi

tz

~fls.d

FIG. 65, A. — Lepus cuniculus. Muscles of the fore-limb, from
the outer side ( x ^).

ab.p, abductor pnllicis : a.br.i, abductor brachii inferior: a.br.s, ab-
ductor brachii superior: an. I, annular ligament : b.hu, basio-humeralis :
bi, biceps : br.i, brachialis internus : cLm, cleido-rnastoid : cp. /, capsular
ligament of shoulder : cr.br, coraco-brachialis : d, deltoid: ex.c.d, ex-
tensor communis digitorum : ex.cp.r, extensor carpi radialis : ex.cp,u,
extensor carpi ulnaris : ev.d.^ extensor quarti digiti : ex.d.$, extensor
quinti digiti : ex.p.a, extensor parvus antibrachii : fl.cfl.r, flexor carpi
radialis : Jl.cp.ii, flexor carpi ulnaris : fl.p.d^, superficial head of flexor
profundus digitorum, its middle portion removed to show the underlying
muscles (C) : fl.p.d*1, ulnar head of the same muscle : Jl.p.d*, its radial
head : Jl.p.d*, its middle head: Jl.s.d, flexor sublimis digitorum : hit,
humerus : i.sp.f, infra-spinous fascia : La, linea alba : l.a.sc, levator
anguli scapulae : l.d, latissimus dorsi : l.sc.m, levator scapulae major :
ob.ex, obliquus externus abdominis : pc.ma, pectoralis major : pc.mi,
pectoralis minor : pc.t, pectoralis tenuis : pi, palmaris: pn.c, panniculus
carnosus: pr.t, pronator teres : r.ab, rectus abdominis : rh.c, rhomboideus
cervicalis : rh.d, rhomboideus dorsalis : sr.fii, serratus magnus : s.sc,
subscapularis : s.sp, supra-spinatus : s.sp.f, supra-spinous fascia : st.hy.
sterno-hyoid : st.m, sterno-mastoid : tc.ina, teres major : tr, trachea :
trl, middle, tr", external, tr*, internal, and t)A, accessory, head of triceps:
tz, trapezius : «/, ulna.

THE RABBIT.

341

trapezius : its fibres are gathered into a comparatively narrow
bundle and inserted into the humerus.

393. Thelevator scapulae major (l.sc.m), a narrow 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.

la.

sr.m

FIG. 65, B. — Lepus cuniculus. Muscles of the fore-liinb, from the
ventral aspect (x i). For references see Fig. 65, A.

394. The cleido-mastoid (Fig. 65, A and B, d.m],
arising with the sterno-mastoid (st.m, § 130), from the
periotic, and passing backward to be inserted into the
clavicle.

395. The basio-humeralis (bJni), 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
scapulae major near their insertions, and reflect them
so as to expose the underlying muscles : note :

r7i.o

s.se

l.a.sc

cp.l

FIG. 65, C. — Lepus cuniculus. Muscles of the fore-limb, from the
inner side ( x ^). For references see Fig. 65, A.

397. The rhomboideus dorsalis (Fig. 65, C, r

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 (rh.c), a long
muscle arising from the hinder surface of the skull and

THE RABBIT. 343

from the spines of the cervical vertebras, and inserted with
the preceding muscle into the supra-scapular border.

399. The serratus magnus (A, B, and C, sr.m), 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.

400. The levator anguli scapulae (l.a.sc), a large
muscle arising from the transverse processes of the last five
cervical vertebras, 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 §§ I3I--I33) ; 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 spinse, 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.t>r.s), a small
triangular muscle arising from the acromion, and inserted
into the deltoid ridge : detach from its origin and reflect.

LI I. Cut through the insertions of the pectoralis minor,
rhomboidei, serratus magnus, and levator anguli
scapulae: 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.

404. The teres major (te.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.

405. 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 (cr.br), 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 tlie outer surface of tJie scapula.

407. The supra-spinatus (s.sp}, 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.br.i) arising
from the infra spinous fascia (i.sp.f) 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 (i.sp), lies beneath the pre-
ceding : it arises from the whole post-scapular fossa and
from the post-axial surface of the spina scapulae, 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.p.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—

(a). The middle or long head (anconeus longus, ^r1),
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.

(/>). The short or outer head (anconeus brevis, tr-}
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, tr6} 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, fr4) is a
very small, fan- shaped muscle, exposed by reflection of the
anconeus lonp-us and internus, on the inner faee of the;

4_> '

346 ZOOTOMY.

elbow-joint : it arises from the inner condyleof the humerus,
and is inserted into the olecranon.

413. The biceps brachii (£/), 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 (br.i), 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

/// the fore-arm 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 (#«./), 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.c.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. Each tendon passes

THE RABBIT.

347

along the dorsal aspect of the corresponding digit, broadens
out into a sort of sheath over the metacarpo-phalangeal

a

flpd fl.cp.r

3 a?

FIG. 66. — Lepus cuniculus. Muscles of the manus. A, dorsal ;
B, ventral (nat. size).

I — 5> the digits : ab.d.$, abductor minimi digiti : ab.p, abductor
pollicis : an. I, annular ligament : ex.c.d, extensor communis digitorum :
ex.cp.r, extensor carpi radialis : ex.cf>.u, extensor carpi ulnaris : ex.d.^9
extensor quart! digiti : ex.d.$, extensor quinti digiti ; ex.p.i, extensor
pollicis et indicis : fl.p.d.m, flexor brevis minimi digiti : fl.p.p, flexor
brevis pollicis \fl.cp.r, flexor carpi radialis : fl.cp.u, flexor carpi ulnaris :
fl.p.d, flexor profundus digitorum : fl.fi. d2, its tendon to the index digit,
cut short : fl.s.d, flexor sublimis digitorum : fl.s.d-, its tendon to the
second digit partly removed, and its distal end reflected : ft.s.d^, 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: io, interossei : lb. 1,7^.2, $.3, lumbricales : r (above),
radius : r (below), retinacula, those of the second digit cut through and
reflected to show the insertion of the flexor sublimis : //, ulna.

34S ZOOTOMY.

and inter-phalangcal articulations, and is inserted into the
middle and distal phalanges : divide and reflect.

417. The extensor pollicis et indicis (ex.p.i), 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 (ab.p), 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.

419. The extensor quart! digit! (ex.d.^), the extensor
quint! digit! (ex.d.^), and the extensor carpi ulnaris
(ex.cp.it), 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 quint! 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 (fccp.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. Thepronatorteres (Fig. 65, C,/r./), 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 (fl.cp.r), a long, slender
muscle arising from the inner condyle of the humerus just

THE RABBIT. 349

posterior to the origin of the pronator teres, and passing
into a long tendon which is inserted into the proximal end
of the second metacarpal : the insertion is best seen at a
later stage : cut through and reflect.

423. The flexor profundus digitorum, or flexor
perforans (fl.p.d\ a large muscle, the chief flexor of the
digits, and made up by the union of four heads-

(a). The superficial head arises from the inner con-
dyle of the humerus just posterior to the origin of the flexor
carpi radialis, and in common with thepalmaris (§ 424) : cut
it through near its origin and reflect.

(b). The ulnar head lies deeper than and anterior to
the foregoing, by the reflection of which it is exposed : it
arises from the inner condyle of the humerus in common
with the flexor sublimis (§ 425).

(<r). The radial head arises from the proximal part of
the posterior surface of the radius.

(d). The middle head arises from .the posterior surface
of the ulna. The four heads unite at the distal end of the
fore-arm to form a common tendon, the insertion of which
is best seen at a later stage of the dissection (§ 427).

424. The palmaris (//), a small, slender muscle arising
with the superficial head of the deep flexor from the inner
condyle of the humerus and passing into a long tendon
which becomes lost in the palmar fascia, or sheet of
connective tissue covering the ventral surface of the manus,
sending off also a small slip which is inserted into the
ungual phalanx of the pollex : cut through and reflect.

425. The flexor sublimis digitorum (fl.s.d\ or flexor
perforatus, lying immediately beneath the superficial head
of the flexor profundus : it arises in common with the ulnar
head of the latter from the inner condyle of the humerus,
and divides distally into four tendons, which pass, superficial

350 ZOOTOMY.

and post-axial to the tendon of the flexor profnndus, into
the manus and along the ventral faces of the second to the
fifth digits : each tendon divides at the base of the proximal
phalanx into two slips which pass one on either side of the
proximal phalanx to be inserted into the proximal end of
the middle phalanx : cut through and reflect.

The tendon for the fifth digit has in connection with it a very small
muscle, the flexor brevis minimi digiti (fl.p.d.m.}, which arises
partly from it, partly from the pisiform bone, and joins the tendon
again at its distal end. A similar muscle, the flexor brevis pollicis
( fl.pp.), arises from the annular ligament and is inserted into the tendon
of the flexor profundus going to the pollex.

426. The retinacula (r\ transverse tendinous bands
which keep the flexor tendons in place : there is one at
the metacarpo-phalangeal articulation, formed by an ex-
pansion of the tendon of the flexor sublimis, one proximal
to the joint between the proximal and middle phalanges,
and another distal to the same joint.

427. The insertion of the flexor profundus : its tendon
spreads out into a broad stout sheath lying immediately
dorsal to the tendons of the superficial flexor : from this
sheet five tendons are given off, one to each digit, each
passing along the ventral face of the digit and being inserted
into its ungual phalanx : the tendons of the second to the
fifth digits pass between the two slips into which the
corresponding tendon of the flexor sublimis is divided.

428. The lumbricales (ll>. i, 2, 3), three small spindle-shaped muscles
arising from the ventral surface of the tendon of the flexor profundus
at the place where it divides into slips for the second to the fifth digits :
they are inserted into the proximal ends of the proximal phalanges
on the pre-axial side of the third, fourth, and fifth digits respectively.

429. The abductor minimi digiti (ab.db\ a small muscle lying on
the ventral face of the fifth metacarpal : it arises from the pisiform
bone, and its tendon joins with that of the superficial flexor going
to the fifth digit.

THE RABBIT. 351

430. The interossei (io), seen, by reflecting the flexor profundus with
the Inmbricales and the flexor minimi digiti, as three pairs of small
muscles lying on the ventral faces of the second to the fourth inetacarpals
and one on the pre-axial side of the fifth rnetacarpal : they arise from
the metacarpals. The two muscles of each pair are in close con-
tact with one another for the greater part of their extent, but
separate distally to be inserted into the sesamoid bones at the meta-
carpo-phalangeal articulation ; a small additional slip occurs on the
post-axial side of the second digit, and one on each side of the fourth :
these are much smaller than, and arise ventrally to, the paired muscles.

LIII. Dissect away the origins and insertions of any
muscles still left attached to the shoulder-joint,
and make out :

431. The capsular ligament surrounding the shoulder-
joint : it consists of thin fibrous tissue, and is attached on
the one hand round the margin of the glenoid cavity
and on the other round the neck of the humerus : if
it has not already been cut, make an incision through it, and
notice that it helps to bound a closed synovial cavity,
between the two bones, lined by a delicate synovial
membrane which secretes a small quantity of synovial
fluid.

432. A similar synovial cavity at the elbow-joint: the
joint is further strengthened by strong lateral ligaments,
which pass, one on the pre-axial side from the humerus to
the radius, the other on the post-axial side from the humerus
to the ulna.

LIV. Make out the muscles of the hind limb, begin-
ning with those which connect it with the trunk :

On the ventral surface of the vertebral column.

433. The psoas magnus (Fig. 67, B, ps.m\ a large
muscle in the lumbar region passing longitudinally back-
wards from the diaphragm to the thigh : it arises from the
last three ribs, the last three thoracic and all the lumbar

352

ZOOTOMY.

n It n •>» \V\Ovw ':, \'\C :J> " . •

LJ M, —

7.a

r.al

ad.m

ttd.2

FIG. 67. — Lepus cuniculus. Muscles of the inner side of the hind
limb : A, superficial, B. deep layer (X 3).

In A the adjoining portions of the abdominal muscles are shown : in
B these are removed so as to show the muscles on the ventral face of
the vertebral column.

ad.b, adductor brevis: ad. I, adductor longus : ad.m, adductor magnus,
its fibres separated in B to show the semi-tendinosus : ex.c.d, extensor
communis digitorum : ex.d.i, extensor prirni digiti : Ji.d.c, flexor coin-

THE RABBIT. 353

munis digitorum : #r, sracilis, removed in B with the exception of its
origin : gsl, inner head of gastrocneinius : /.a, linea alba, Ig.pa, liga-
mentuin patella: ob.ex, obliquus externus abdominis : pc, pectineus :
//, plantaris : q.lb, quadratus lumbmun: qu.i, superficial head of
rectus anticus : qu.i1, its deep head: qu.2, vastus internus, mostly
removed in B : qu.^, crureus : r.ab, rec'us abdominis : sa, sartorius,
removed in B : s,m, semi-membranosus : s.t, semi-tendinosus : t.ach,
tendo Achillis : tb.a, tibialis anticus.

vertebrae : in its anterior half it forms the inner slope of the
great longitudinal muscular ridge, which lies close to the
middle line and has embedded in it the long transverse
processes of the lumbar vertebrae : at about the middle of
its course it turns outwards and is inserted into the lesser
trochanter of the femur: its insertion is best seen after
some of the muscles of the thigh have been removed (§ 448).

434. The quadratus lumborum (q.lb), a large muscle
lying just external to and having the same general direction
as the preceding : it forms the external slope of the muscular
ridge mentioned above, as well as the whole of its deeper
portion : it consists of two parts separated by the transverse
processes of the lumbar vertebrae, the inner arising from the
last five thoracic and all the lumbar vertebrae, the outer from
the five last ribs and corresponding transverse processes and
from all the lumbar vertebrae : it is inserted partly into the
lumbar vertebrae, partly into the pubic border of the ilium.

435. The psoas parvus (ps.p\ lying internal to about
the posterior half of the psoas magnusr it arises from the
bodies of the four posterior lumbar vertebrae, and is inserted
into the pubis by a tendon which acquires a connection
with Pou part's ligament (p.lg).

436. The iliacus (//), a broad muscle, arising from the
ventral faces of the last lumbar and first sacral vertebras, and
passing obliquely outwards and backwards to be inserted,
along with the psoas magnus, into the lesser trochanter
(§44«).

A A

354 ZOOTOMY.

In the thigh and Jiip.

437. The fascia lata, or strong fibrous covering of the
muscles of the thigh : it is especially thick on the outer side :
dissect it away so as to expose the underlying muscles,
taking care not to injure any of the latter, some of which
are closely attached to the fascia.

438. The sartorius (Fig. 67, A, sa), a small flat muscle
on the inner face of the thigh, about midway between its
anterior and posterior borders : it arises from the middle of
Poupart's ligament, and passing obliquely outwards blends
with the anterior edge of the gracilis (§ 439).

439. The gracilis (gr\ a large thin sheet of muscle
covering the greater part of the posterior half of the inner
surface of the thigh : it arises from the whole of the
symphysis pubis, and passes distally into a broad fascia
which is inserted into the upper part of the inner (pre-axial)
border of the tibia : separate it from the underlying muscles,
cut it through, and reflect along with the sartorius.

440. The quadriceps (Figs. 67 and 68, qu\ or great
extensor of the crus, a very large muscle forming the anterior
part of the thigh : it consists of several parts—

(a). The long or superficial head of the rectus
anticus (qu. i), forming the anterior edge of the thigh : it
arises from the pubic border of the ilium, and is inserted by
a strong thick tendon, the ligamentum patellae (Ig.fci),
in which the patella is embedded, into the crest of the tibia :
carefully separate it from the underlying muscles, cut through
and reflect.

On the dorsal surface of the thigh the edge of the rectus is produced,
near its proximal end, into a somewhat semicircular expansion which is
inserted into the fascia lata : this represents what is usually a separate
muscle, the tensor vaginae femoris or tensor fasciae latae.

The vastus internus (qu.i), occupying the space, on

THE RABBIT.

355

the inner surface of the thigh, between the rectus anteriorly
and the sartorius and gracilis posteriorly : it arises from the

c2

a.n.1

fid.c

FIG. 68. — Lepus cuniculus. Muscles of the outer side of the hind
liinb : A, superficial, B, deep layer (X £)•

ac, acetabulum : ad. I, adductor longus : ad.m, adductor rnagnus :
an. I, annular ligament : bil, superficial head of biceps femoris : />/2, its
deep head, reflected in B to show its double origin : d, calcaneum :
c.l.l, external lateral ligament of knee : er.sp, erector spinae : fl.d.c,
flexor communis digitorum : gl.ma, gl.ma', gtuteus rnaxiruus : gl.me,
gluteus medius : ^l.nii, gluteus minimus: gm.a, gemellus anterior:
gl.pt gemellus posterior : gr, gracilis : qs1, outer head of gastrocnemius,
turned aside in B to show the soleus : Ig.fia, ligamentum patellae :
ob.ex, obliquus externus : 0*1, i, obturator internus : //, plantaris : //,
popliteus : pr, peronei (in A) : pr.b, peroneus brevis : pr.d.^, peroneus
f|iiarti digiti : pr.d.$, peroneus quinti digiti : pr.l, peroneus iongus :
py, pyriformis : qu.\, superficial head of rectus anticus : qtt.i1, its deep
head : qu.^, superficial head of vastus externus : tf/<-31, its deep head :
q.fm, quadratus femoris : r.ab, rectus abdominis : s.m, semi-mem-
branosus : so, soleus: ti, tibia: ti.a, tibialis anticus: tr.i, great
trochanter : tr.^, third trochanter : tu.is, tuber ischii.

A A 2

356 ZOOTOMY.

neck of the femur, and at its distal end joins the rectus in the
ligamentum patellae : cut through and reflect.

(f). The principal or superficial head of the vastus
externus (^.3), situated just posterior to the rectus
anticus on the outer surface of the thigh : it is the largest
head of the quadriceps : it arises from the neck of the femur
and from the great trochanter, and passes distally into the
common tendon of the quadriceps or ligamentum patellae.

The short or deep head of the rectus anticus
1), a cylindrical muscle lying along the inner or pre-axial
side of the vastus externus, by which it is partly enwrapped :
it arises from the posterior part of the pubic border of the
ilium, and passes distally into the common tendon of the
quadriceps.

(e). The accessory or deep head of the vastus
externus (^^•31), a flattish muscle, lying between the
concave inner face of the superficial head and the crureus
(see below) : it arises from the femur close to the origin of
the superficial head, and distally joins the ligamentum
patellae : cut through and reflect both heads of the vastus
externus and the short head of the rectus.

(/). The crureus (^#.4), arising from the shaft of the
femur, the anterior (dorsal) surface of which it covers, and
passing distally into the commom tendon of insertion of the
quadriceps : detach it from its origin and reflect.

441. The biceps femoris (/;/), covering the posterior
half of the outer side of the thigh and forming the chief
flexor of the cms : it has two heads, of which the first or
anterior head (bil) arises by a wide flat tendon from the
three posterior sacral and the three anterior caudal vertebrae,
and passes outwards, gradually diminishing in breadth and
becoming sub-cylindrical : the second or posterior head
arises from the posterior part of the tuber ischii in

THE RABBIT. 357

common with the adductor magnus (§ 443)> and passes
outwards, widening as it goes : the two heads unite, and are
inserted by a strong and extensive fascia into the distal end
of the femur and proximal end of the tibia. Cut through
both heads and reflect : it will be seen that the posterior
head has a second origin in the form of a flat tendon arising
in common with the semi-membranosus (§ 442) from the
anterior end of the tuber ischii.

442. The semi-membranosus (s.m), forming the
posterior edge of the thigh : it arises from the tuber ischii in
common with the accessory tendon of the posterior head of
the biceps, and is inserted by the same fascia as the gracilis
into the proximal part of the pre-axial border of the tibia :
from the distal end of its posterior edge proceeds a long
tendon which passes along the inner side of the shank and
joins the tendo Achillis (§ 460) : cut through and reflect.

443. The adductor magnus (ad.m\ a large fleshy
muscle in the posterior region of the thigh, fully exposed by
the removal of the gracilis, which covers its inner face, and
of the semi-membranosus and biceps, which cover its outer
face : it arises from the posterior edge of the ischium and
tuber ischii, and is inserted into the inner side of the distal
end of the femur and inner condyle of the tibia.

444. The semi-ten dinosus (/./), seen by separating
the fibres of the adductor magnus in which it is embedded :
it is a long spindle-shaped muscle, arising from the tuber
ischii and inserted by a long tendon, which emerges from
the adductor magnus near the distal end of its outer surface,
into the inner condyle of the tibia : cut through and reflect
both semi-tendinosus and adductor magnus.

445. The adductor longus (ad. I), a large, somewhat
triangular muscle, forming the main part of the mass of flesh
still left posterior to the femur : it arises from the whole of

358 ZOOTOMV.

the symphysis pubis, and is inserted into about the middle
third of the shaft of the femur.

446. The adductor brevis (ad.b), a small, flat muscle
situated just anterior to the inner two-thirds of the preced-
ing : it arises from the anterior end of the symphysis pubis,
and is inserted by a broad tendon into the shaft of the
femur.

447. The pectineus (pc), a small muscle situated
immediately in front of the preceding, which it resembles
in shape and size : it arises from the pubis just in front of
the symphysis, and is inserted into the shaft of the femur :
cut through and reflect it as well as the adductores brevis
and longus.

448. The insertions of the psoas magnus (§ 433) and
iliacus (§ 436) are now exposed : divide both muscles near
their insertion and reflect.

449. The gluteus maximus (gl.ma\ covering the outer
or gluteal surface of the ilium : it arises by a broad fascia
from the ischial border of the ilium and from the sacrum :
anteriorly it becomes inseparably united with the rectus
anticus, posteriorly its origin is covered by the anterior head
of the biceps : it consists of two parts, one lying mainly
external to the pubic border of the ilium and having its
fibres directed longitudinally, the other at about the level of
the acetabulum and having its fibres directed transversely :
the two portions unite with one another and are inserted
into the third trochanter : detach from its origin and
reflect.

450. The gluteus niedius (gl.me), exposed by removal
of the preceding : it arises from the supra-iliac and iliac
borders of the ilium and from the sacrum : its fibres pass
directly backwards, and are inserted into the great trochanter :
detach from its origin and reflect.

THE RABBIT. 359

451. The gluteus minimus (gl.mi), exposed by the
reflection of the preceding : it arises from the whole gluteal
fossa of the ilium from its supra-iliac and iliac borders and
from the first sacral vertebra : it is inserted into the great
trochanter

452. The pyriformis (/_>'), a triangular muscle, lying
immediately posterior to the gluteus minimus : it arises from
the second and third sacral vertebrae, and passes directly out-
wards to be inserted into the great trochanter, beneath the
insertion of the gluteus medius, and posterior and dorsal to
that of the gluteus minimus : divide and reflect : also detach
the gluteus minimus from its origin and reflect.

453. The quadratus femoris (q.fai), a small stout
muscle lying parallel to the inner edge of the adductor
longus : it arises from the tuber ischii, and is inserted into
the posterior (ventral) side of the shaft of the femur at about
the level of the third trochanter : divide and reflect.

454. The obturator internus (<;/>./), a flat muscle
arising from the dorsal or inner aspect of the obturator
foramen, and passing first upwards, then outwards and for-
wards, to be inserted into the trochanteric fossa : to see its
origin the caudal vertebrae should be pressed aside.

455. The gemelli, two very small muscles in connection \vith the
preceding : the gemellus anterior (gtn.a) arises from the dorsal edge
of the ischium and partly covers the anterior edge of the obturator
internus ; the gemellus posterior (gl.p) arises from the tuber ischii
and covers its posterior border : both are inserted into the tendon of the
obturator internus.

456. The obturator externus, arising from the outer
or ventral aspect of the obturator foramen, and inserted by a
strong tendon into the trochanteric fossa : detach the

O

obturatores from their origin and reflect.

360 ZOOTOMY.

In the shank and foot.

457. The tibialis anticus (Figs. 67, 68, and 69, tb.a\
forming the anterior border of the shank : it arises from
the outer tuberosity of the tibia and from its cnemial
crest, and is continued distally into a long tendon, which
passes under a strong annular ligament (anJ) placed
obliquely at the distal end of the anterior surface of the
femur : entering the foot the tendon of the tibialis anticus is
inserted into the proximal end of the second (apparent first)
metatarsal : divide and reflect, firsf separating carefully from
the next muscle.

458. The extensor communis digitorum (ex.c.d),
situated between the tibia and the tibialis anticus, and
closely applied to the latter : it arises by a long tendon from
the anterior surface of the distal end of the femur just
external to the intercondylar notch : to see this origin the
tendon must be traced through the capsule of the knee-
joint (§ 474) : distally the muscle divides into four tendons,
which pass through the annular ligament, then through a
similar but smaller loop on the dorsal surface of the carpus,
and are inserted into the phalanges of the four digits in the
same manner as the corresponding muscle of the hand
(§ 416) : divide and reflect.

459. The extensor digit! primi (properly secondi)
(ex.d.i.), arising from the inner tuberosity of the tibia, and
passing along the inner aspect of the crus, at about the
middle of which it becomes tendinous : this tendon runs in
a groove on the pre-axial side of the distal end of the tibia,
beneath (ventral to) the curved proximal end of the second
metatarsal, curves over to the dorsal side of the latter, and
unites with the first tendon of the common extensor on the
dorsal surface of the proximal phalanx : divide and reflect.

460. The gastrocnemius (gs\ a large two-headed

THE RABBIT.

tb

-fl.d.c

an

ex.d

fid,

FIG. 69. — Lepus cuniculus. Muscles of the pes : A, dorsal,
B, ventral (nat. size).

2 — 5, the digits : tx.c.d, extensor communis digitomm : ex.d.i,
extensor primi (properly secondi)digiti \fl.d.c, flexor communis digitorurn :

362 ZOOTOMY.

fl.d.c-, its tendon to the second digit, in great part removed to show the
interossei: fl.d.c5, its tendon to the fifth digit: i.o, interossei : lb.it
lb.2, lb.3, lumbricales : pi, plantaris : pi'1, its tendon to the second digit,
partly removed and with its distal end reflected : //4, its tendon to the
fourth digit, partly removed, and having the sheath it forms over the
metatarso-phalangeal articulation slit up and reflected right and left :
pr.b, peroneus brevis : pr.d.^, peroneus quarti digiti : pr.d.$, peroneus
quinti digiti : pr.l, peroneus longus : t.ach, tendo Achillis, inserted into
the calcaneum : tb.a, tibialis anticus : //, tibia.

muscle forming the posterior surface of the shank : its
inner head (qsl) arises from the inner condyle of the
femur and pre-axial fabella (§ 94), its outer head (qs2)
from the outer condyle and post-axial fabella : the two heads
unite with one another and with the soleus (§ 461) to form
a large strong tendon, the tendo Achillis, which is
inserted into the extremity of the calcaneum.

461. The soleus (JT<?), a small muscle seen by turning
aside the outer head of the gastrocnemius ; it arises by a
long tendon from the head of the fibula, and joins the
gastrocnemius to form the tendo Achillis.

462. The plantaris (//), a large muscle, the proximal
fleshy part of which is enwrapped by the gastrocnemius, from
which it must be carefully separated : by dividing and
reflecting the gastrocnemius and soleus, the plantaris is seen
to arise from the posterior surface of the femur immediately
proximal to the outer condyle and from the post-axial fabella :
at about the middle of the crus it passes into a strong flat
tendon, which curves round to the posterior side of the tendo
Achillis and over the end of the calcaneum to reach the sole
of the foot: the tendon divides into four slips, which are
related to the digits in the same way as those of the flexor
sublimis to the digits of the manus (§ 425) : divide and
reflect.

463. The popliteus (//>), or rotator of the knee, lying
obliquely across the back of the knee-joint : it arises by

THE RABBIT. 363

a strong tendon from the outer condyle of the femur, passes
backwards beneath the external lateral ligament (§ 474), and
curves round the posterior surface of the proximal end of
the tibia to be inserted into the pre-axial edge of that
surface : divide and reflect.

464. The flexor digitorum communis (fl.d.c), closely
applied to the posterior surface of the tibia : it arises from
the outer tuberosity of the tibia and from the head of the
fibula : its tendon enters the foot to the inner or pre-axiai
side of the calcaneum, then expands and divides into two,
each subdivision soon dividing again : the four slips thus
formed have the same relation to the digits as those of the
flexor profundus to the digits of the manus (§ 427).

465. The lumbricales (/£), three very small spindle-shaped muscles
arising from the tendon of the preceding, and inserted on the pre-axial
sides of the proximal ends of the proximal phalanges of the third, fourth,
and fifth digits respectively.

466. The peroneus longus (pr.l), a long, slender
muscle arising from the outer tuberosity of the tibia : it
passes into a long tendon which traverses a groove on the
post-axial side of the distal end of the tibia, and is inserted
into the cuboid : divide and reflect.

467. The peroneus brevis {pr.b\ arises from the outer
tuberosity of the tibia, partly united with the peroneus quarti
digiti ; its tendon accompanies that of the peroneus longus,
and is inserted into the proximal end of the fifth (last)
metatarsal.

468. The peroneus quarti digiti (pr.d.\), arises from
the shaft of the fibula, being united at its origin with the
preceding : its tendon enters the foot with those of the
other peronei, and is inserted into the distal end of the fourth
(apparent third) metatarsal.

469. The peroneus quinti digiti (pr.d.$), arises from

364 ZOOTOMY.

the head of the fibula, united with the preceding : its tendon
passes with those of the other peronei into the foot, and is
inserted into the distal end of the last metatarsal.

470. The interossei (i.o) have the same general disposition as those
of the manus (§ 430), there being a pair on the ventral or plantar side of
each metatarsal : there are also two very slender slips, one on the
post-axial side of the second (apparent first), another on the pre-axial
side of the fourth metatarsal.

LV. Dissect away the origins and insertions of any
muscles still left attached to the hip and knee-
joints, and make out :

471. The capsular ligament of the hip-joint, a mem-
brane attached on the one hand just external to the rim of
the acetabulum and on the other round the neck of the
femur : partly remove it so as to see the synovial cavity
which it helps to enclose.

472. The ligamentum teres, exposed by the severance
of the capsular ligament : it is a strong band of fibres
passing from the bottom of the acetabulum to the pit on the
head of the femur (§ 93).

473. The cotyloid ligament, a rim of nbro-cartilage attached round
the edge of the acetabulum.

474. The capsular ligament of the knee-joint, bound-
ing its synovial cavity, which will have been opened in
tracing the tendon of the extensor communis digitorum : it
is strengthened in front by the ligamentum patellae
already seen (§ 440), and at the sides by the internal and
external lateral ligaments, which pass respectively from
the inner and outer tuberosities of the femur to the cor-
responding tuberosities of the tibia.

475. The inter-articular ligaments, extending be-
tween the actual articular surfaces of the femur and tibia,

• THE RABBIT. 365

and connecting the semi-lunar cartilages (§97) with one or
other bone.

The posterior ligament extends from the inner (post-axial) face of
the internal condyle of the femui obliquely downwards to about the
middle of the posterior edge of the articular surface of the tibia : the
anterior crucial ligament extends from the inner (pre-axial) face of
the external condyle of the femur to the anterior part of the articular
surface of the tibia, near the middle line : the posterior crucial
ligament extends from a point within the external coudyle of the femur
and immediately proximal to the attachment of the posterior ligament,
obliquely downwards and outwards to the posterior end of the post-
axial semi-lunar cartilage ; it is continued from the anterior end of the
same cartilage, passes inwards in front of the tibial attachment of the
anterior crucial, and is attached near the inner border of the articular
surface of the tibia : the internal or pre-axial semi-lunar cartilage has a
ligament at its anterior end which crosses in front of the posterior
crucial to be inserted into the articular surface of the tibia near the
middle of its anterior region ; a similar ligament from the posterior end
of the cartilage is inserted immediately in front of the tibial attachment
of the posterior ligament.

LVI. In the brain, dissect off the pia mater, taking
special care not to remove the nerve roots (§§
488-495) or the arteries (§ 476) with it : the latter
may, however, be removed as soon as seen.
Make out the following points without further
dissection : l

476. The circle of Willis, an arrangement of arteries
on the base of the brain, due to the anastomosis of the
vertebrals and internal carotids, and forming a sort of
hexagonal figure round the optic chiasma (§ 486), infun-
dibulum (§ 485), and corpus mammillare (§ 487).

The vertebral arteries, entering the foramen magnum, unite on the
ventral surface of the medulla oblongata (§ 477) to form the median

1 It is best, if possible, to dissect two brains simultaneously, one
fresh, the other well hardened : if only one is used, it should be only
moderately hardened — say in alcohol of about 70 per cent.

366 ZOOTOMY.

longitudinal basilar artery : this passes forwards, sending off branches
to the medulla oblongata and cerebellum (§ 478), and just anterior to
the pons VaroJii (§ 479) bifurcates, forming the paired posterior
cerebral arteries : the internal carotids reach the base of the brain at
about the level of the optic chiasma, and each divides into the anterior
cerebral artery directed inwards and forwards, and the middle cere-
bral directed outwards : the " circle " is completed by the two anterior
cerebrals uniting to form a median trunk which passes forwards between
the cerebral hemispheres, and by the union of each internal carotid to
the corresponding posterior cerebral by a slender posterior com-
municating artery.

477. The medulla oblongata, directly continuous
with the spinal cord through the foramen magnum, and
resting, when in the skull, on the basi-occipital. It is
composed externally of white matter, and is marked on its
upper and lower surfaces respectively by the dorsal and
ventral fissures, continuous with the similar and similarly
named structures in the spinal cord : on each side of the
ventral fissure is a narrow longitudinal elevation, the ventral
pyramid (Fig. 70, ?'./), immediately external to the anterior
part of which is a band of transverse fibres, the corpus tra-
pezoideum (c.tz) : posterior to each corpus trapezoideum,
and bounded internally by the ventral pyramid, is an area
(ol.b) answering to the olivary body of the higher mam-
malian brain : on each side of the dorsal fissure is the
narrow dorsal pyramid (Fig. 71, </./), of which at present
only a small part is seen (see § 522) : external to this, and
forming the dorso-lateral region of the medulla, is the
corpus restiforme (c.rs).

478. The cerebellum (cb), on the dorsal side of the
medulla oblongata; a greatly convoluted body, composed
externally of grey matter, and consisting of a central lobe
or superior vermis (cbl\ two lateral lobes (cb'2}, and
two irregular globular bodies (flocculi, fl), each of which

THE RABBIT.

367

projects laterally outwards from the corresponding lateral
lobe, and fits into a deep pit in the cranial wall of the periotic
bone (§ 56).

479. The pons Varolii (p.va), a strong band of white
fibres running transversely across the anterior part of the

ol.b

m.o

FIG. 70. — Lepus cuniculus. The brain from beneath (nat. size).

cb~, lateral lobe of cerebellum : c.h^, frontal, and cjr, temporal, lobe
of central hemisphere : c.ma, corpus mammillare : c.tz, corpus trape-
zoideum : fl, flocculus : m.o, medulla oblongata : o.ch, optic chiasma :
ol.b, olivary body : olf, olfactory lobe : o.tr, optic tract : pty, pituitary
body : p.va, pons Varolii : v.p, ventral pyramid : // — XII, roots of
cerebral nerves : j/1, first spinal nerve.

ventral surface of the medulla oblongata immediately in
front of the ventral pyramids and corpora trapezoidea : it
ends in front in a forward! y curved margin, and is marked

36S ZO&TOMY.

by a median groove, continuous with that of the medulla,
and lodging the basilar artery. Laterally, the fibres of
the pons bend upwards and enter the cerebellum, forming
its middle peduncles.

480. The cruracerebri (c.c), two strong diverging bands
of white fibres on the ventral surface of the brain, pro-
ceeding forwards and outwards from the anterior edge of
the pons Varolii.

481. The cerebral hemispheres (cJi), two large
masses which constitute the greater part of the brain : they
are closely applied to one another along their flat inner
faces ; broad and somewhat truncated posteriorly (parietal
lobes), where they abut against the cerebellum ; pro-
duced into a blunt point anteriorly (anterior or frontal
lobes, c.h1} ; and produced downwards into the prominent
temporal lobes (c.h-) which partly overlap the crura
cerebri. Where the temporal becomes continuous, ven-
trally, with the frontal lobe is a slight angulation, the
rudimentary Sylvian fissure. The surface of the hemis-
pheres is formed of grey matter, and is smooth except for
one or two slight depressions or sulci.

482. The corpus callosum (cp.d), seen, by slightly
separating the hemispheres from one another above, as a
strong white transverse band, connecting them with one
another along the middle third of their length.

483. The pineal body (pri) and a portion of the optic
lobes (o.l1, o.P) (§§ 517 and 519) are seen on the dorsal
surface of the brain, between the cerebrum and cerebellum.

484. The olfactory lobes (off), two knob-like bodies
of grey matter proceeding forward from the anterior part of
the ventral surface of the hemispheres, and connected by a
strong white band with the anterior edge of the temporal
lobe. They fit into the deep olfactory fossae of the skull,

THE RABBIT. 369

and from their lower and front surfaces are given off the
filaments of the first or olfactory nerve.

485. About the centre of the base of the brain, between
the temporal lobes of the cerebral hemispheres, is a slight
elevation pierced in the centre by a small aperture ; the
elevation is the infundibulum ; to it is attached in the
perfect state of the brain the oval, vascular pituitary
body (pty\ which in removing the brain is almost always
left behind in the sella turcica (§ 48).

486. Immediately in front of the infundibulum is a
strong, curved, transverse band of white fibres, giving
off from its convex anterior margin two strong nerves.
The latter are the optic nerves (77) : the transverse
band is constituted by the two optic tracts (o.tr),
which, together with the nerves, form the optic chiasma

(O.C/1).

487. The corpus mammillare (c.ma), a rounded eleva-
tion immediately posterior to the infundibulum, in the angle
between the crura cerebri.

488. The oculomotor nerves (third pair, 777), arising
one from each cms cerebri, slightly posterior to the corpus
mammillare.

489. The pathetic nerves (fourth pair, 7F), arising
from the anterior part of the dorsal surface of the medulla
oblongata (valve of Vieussens, § 523), and passing outwards
and downwards between the cerebrum and cerebellum to
reach the ventral surface of the brain : their origin will be
best seen at a later stage.

490. The trigeminal nerves (fifth pair, F), arising
from the postero-external region of the pons : each consists
of two roots, a large external sensory, and a small internal
motor root.

491. The small abducent nerves (sixth pair, VI\

a B

ZOOTOMY.

arising from the external edges of the anterior pyramids of
the medulla, just posterior to the pons.

492. The facial nerves, or portiones durse (seventh
pair, VI I \ arise from the lateral regions of the ventral
surface of the medulla, just posterior to the corresponding
nerves of the fifth pair; their fibres pass directly outwards.

493. The auditory nerves, or portiones molles
(eighth pair, VIII), arise close behind and slightly external
to the facials ; each divides immediately into two large
trunks, which pass outwards, parallel with the corresponding
seventh nerve.

494. The glossopharyngeal nerves (ninth pair, IX),
vagi or pneumogastric nerves (tenth pair, X), and
accessory nerves (eleventh pair, XI), arise, in the order
mentioned, from the lateral regions of the medulla, just
posterior to the cerebellum, and so close to one another that
they may easily be mistaken for a single pair. If a sufficient
length of the spinal cord has been removed along with the
brain, the accessory will be seen to be formed by a slender
nerve which arises from the spinal cord slightly posterior to
the fifth spinal nerve, and passes forwards, receiving fibres
from the cord as it goes, between the dorsal and ventral
roots of the first five spinal nerves.

495. The hypoglossal nerves (twelfth pair, XII)
arise from the external edges of the anterior pyramids of
the medulla, slightly posterior to the three preceding nerves ;
each is formed by the union of several strands, which closely
resemble those of the ventral root of a spinal nerve.

LVIL Place the brain with its dorsal side upwards,
and carefully remove successive slices from one of
the hemispheres parallel to its upper surface, until
the upper surface of the corpus callosum is reached
(be careful not to go beyond this point, or some

THE RABBIT.

37i

cp.cl.

st.l

C.TS

C.Tf.

FIG. 71. — Lepus cuniculus. Two dissections of the brain, from
above (nat. size).

In A the left cerebral hemisphere is dissected down to the level of the
corpu; callosum : on the right side the lateral ventricle is exposed. In
B the cerebral hemispheres are dissected down to a little below the level
of the anterior genu of the corpus callosum : only the frontal lobe of
the left hemisphere i; retained, of the right a portion of the temporal
lobe also is left : the velum interpositum and pineal body are removed,
as well as the greater part of the body of the fornix, and the whole of
its left posterior pillar: the cerebellum is removed with the exception of
a part of its right lateral lobe.

a. co, anterior commissure : a.fo, anterior pillar of fornix : a.pn, anterior
peduncles of cerebellum : b.fo, body of fornix : cbl, superior vermis
of cerebellum : cl>', its lateral lobe : c.gn, corpus geniculatum : c.h,
cerebral hemisphere: ch.pl, choroid plexus: cp.cl, corpus callosum
cp.s, corpus striaturn : c.rs, corpus restiforme : d.p, dorsal pyramid
JJ, flocculus : hpjn, hippocampus major : m.co, middle commissure
o.l1, nates: o.l*. testes : o.th, optic thalamus : o.tr, optic tract: p.co,
posterior commissure : p.fo, posterior pillar of fornix : pn, pineal body :
pd.pn, peduncle of pineal body : p.pn, posterior peduncles of cere-
bellum : p.va, fibres of pons Varolii forming middle peduncles of
cerebellum : spju, septum lucidum : st.l, stria longitudinalis : t.s, toenia
;;emicircularis : v.vn, valve of Vieussens : z>-3, third ventricle: ^.4,
fourth ventricle.

B B 2

372 ZOOTOMY,

of the structures in the lateral ventricle, § 498,
may be injured). Note :

496. The central mass of white matter in each hemisphere,
and the superficial grey matter.

497. The fibres of the corpus callosum, passing horizon-
tally outwards on each side, those in front curving slightly
forwards, those behind slightly backwards, to enter the sub-
stance of the hemispheres (Fig. 71, A, cp.d). Near the middle
line the surface of the corpus callosum is marked by two fine
white longitudinal lines, the striae longitudinales (st.t).

LVIII. In laying bare the corpus callosum, a cavity, the
lateral ventricle (§ 498) will probably have been
cut into : if not, carefully scrape away the brain
substance near the centre of each hemisphere,
about a quarter of an inch external to the pos-
terior boundary of the corpus callosum, until the
cavity is met with : lift up the edges of the
aperture, and with fine scissors cut away the
roof of the lateral ventricle, including the corpus
callosum, so as to expose the whole cavity on
the one side, to within one-sixteenth of an inch
of the middle line of the corpus callosum.
Make out :

498. The lateral ventricles (Fig. 71, A, right side), or
cavities of the cerebral hemispheres, each of which is widest
in the middle (body of the lateral ventricle), tapers off
almost to a point anteriorly (anterior cornu), and ends
behind somewhat bluntly.

499. The hippocampus major (hf.m\ a large white
eminence, of nearly semicircular section, forming the floor
of the body of the lateral ventricle, and extending outwards
and backwards : internally it passes into an area, the lyra,
by which it is united with its fellow of the opposite side.

THE RABBIT. 373

500. The septum lucidum (sp.lu), a somewhat tri-
angular body, formed externally of grey matter, lying
beneath the anterior end of the corpus callosum and
immediately in front of the anterior end of the hippo-
campus : it forms the inner wall of the anterior cornu of
the lateral ventricle.

501. The choroid plexus (ch.pt), an extremely vascular
membrane lying in a depression just in front of the hippo-
campus major, and passing beneath the corpus callosum
to join its fellow of the opposite side through a transverse
passage, which puts the third ventricle (§ 513) in com-
munication with the lateral ventricles ; this passage is the
foramen of Monro. The connection of the two choroid
plexuses through the foramen of Monro is best seen by
exerting a slight traction on one of them.

502. The corpus striatum (cp.s), an eminence of grey
matter forming the floor of the anterior cornu of the
lateral ventricle, and separated from the septum lucidum
and hippocampus major by the depression in which the
choroid plexus lies.

LIX. Dissect the other hemisphere in the same way,
observing the same points again, and noting further :

503. The connection of the corpus callosum with the
underlying parts of the brain, namely with the lyra behind
and with the septum lucidum in front.

504. By dividing the corpus callosum transversely, care-
fully separating its two ends from the underlying parts and
reflecting them, it is seen to bend slightly downwards at its
anterior end, forming the anterior genu, while at its
posterior end it bends sharply downwards and then forwards,
forming the posterior genu.

505. By the removal of the corpus callosum the septum
lucidum is found to consist of two layers, between which is

374 ZOOTOMY.

included a space answering to the fifth ventricle of the
higher mammalia, but evidently a portion of the space
between the right and left hemispheres.1

LX. Trace the course of the hippocampus major by

carefully cutting away the outer part of the temporal

lobe : note :

506. The descending cornu of the lateral ventricle,
exposed by the removal of the outer wall of the temporal
lobe ; it passes first almost directly outwards, then down-
wards, and finally inwards and forwards. The hippo-
campus major is continued the whole distance along its
inner wall.

507. The posterior pillar of the fornix (Fig. 71, B,
p.fo}, a. flat white band forming the projecting anterior edge
of the hippocampus major, and continued with the latter
into the descending cornu. Anteriorly it becomes con-
nected with its fellow of the opposite side just behind the
septum lucidum, forming the body of the fornix.

508. The tsenia semicircularis (/.j-), a thin band of
white matter, just in front of the posterior pillar of the
fornix, and forming a sort of bed for the choroid plexus.

509. The fissure of Bichat, a slit-like space between
the taenia semicircularis and the posterior pillar of the
fornix ; it leads on to the under surface of the brain,
between the anterior and inner edge of the temporal lobe
and the optic tract.

LXI. Make a transverse incision through the body of
the fornix, immediately over the foramen of

1 In the higher mammalia, e.g. man, the ?eptum lucidum becomes
very thin and translucent, whence its name, and, the anterior genu of
the corpus callosum being very well developed, and turning round the
anterior edge of the septum lucidum, the latter takes on the form of a
double membrane, situated between the corpus callosum above and in
front, and the body of the fornix (§ 507) behind.

THE RABBIT. 375

Monro, cutting down to the latter : from the
middle of this cut take a longitudinal incision
backwards through the lyra : press aside the
posterior portion of the hemispheres, now com-
pletely separated from one another, and make
out :

510. The hippocampal sulcus, a deep, curved groove
on the inner face of the temporal lobe, corresponding
with the elevation of the hippocampus major.

511. The velum interpositum, a delicate vascular
membrane, continued backwards from the conjoined choroid
plexuses, and forming a roof to the third ventricle (§ 513).

512. The optic thalami (o.t/i], large masses of mixed
grey and white matter, separated in front from the corpora
striata by the depression in which the tsenui semicircularis
lies, and covered dorsally by the velum interpositum.

513. By removing the velum interpositum the third
ventricle (v.$) is exposed ; it is a median vertical fissure,
with which the lateral ventricles communicate, anteriorly,
by the foramina of Monro.

514. The anterior commissure (a.co\ a narrow band
of white fibres, passing transversely, immediately in front of
the third ventricle, between the corpora striata.

515. The anterior pillars of the fornix (a.fo\ a
pair of delicate, vertical, white bands (cut short by the
severance of the body of the fornix), which pass directly
downwards immediately posterior to the anterior com-
missure.

516. The middle or soft commissure (m.co)t a wide
mass of grey matter, passing between the optic thalami
nearly level with their dorsal surface, and, in an upper view,
almost obliterating the cavity of the third ventricle.

517. On the upper surface of the hinder half of each

376 ZOOTOMY.

optic thalamus is a thin white band, the peduncle of the
pineal body (p.pri) : the two peduncles jgin with one
another at the posterior boundary of the thalami, and are
continued into a flat band about a quarter of an inch long,
which ends at the posterior boundary of the cerebral hemis-
pheres in a rounded vascular mass : this is the pineal
body : it rests on the dorsal surface of the optic lobes.

518. The posterior commissure (p.co), seen by
turning aside the stalk of the pineal gland : it is a delicate
transverse band of white fibres, somewhat smaller than the
anterior commissure, connecting the thalami with one
another just below the junction of the peduncles of the
pineal body.

519. The optic lobes, or corpora quadrigemina
(<?./), two pairs of rounded elevations, composed externally
of grey matter, and lying immediately above the crura
cerebri, and bounded by the optic thalami in front and
by the cerebellum behind. The anterior larger pair are
regularly ovoidal in shape, and are called the nates (o.l1} :
the posterior pair, or testes (<?./2), are transversely elon-
gated, and lie at a lower level than the nates.

520. By removing the remainder of the temporal lobe
of one side, the optic tracts (p.tr, § 486) are seen to curve
round the antero-external corner of each optic thalamus,
from the chiasma, and then to pass backwards and inwards
to the nates.

521. The corpus geniculatum (c.gii), a small rounded
elevation on the external surface of the optic thalamus,
immediately posterior to the optic tract.

LXIL Cut away the whole of the central part of the
cerebellum,, leaving only its points of attachment,
at the sides, to the medulla oblongata. Note :
22. The fourth ventricle (z'-4), a flat, lozenge-shaped

THE RABBIT. 377

*

cavity, bounded laterally by the dorsal pyramids- of the
medulla, and roofed in by the cerebellum and the pia
mater. Its floor is marked by a median groove, ending
posteriorly in a pointed depression, the calamus scrip-
torius, which leads into the central canal of the spinal
cord.

523. The valve of Vieussens (v.vn), a thin transverse
band, forming a sort of ledge over the anterior end of the
fourth ventricle, and connected by its anterior edge with
the testes ; the fourth pair of nerves spring from its upper
surface : beneath it is a small aperture leading into the
aqueduct of Sylvius (§ 526).

524. The anterior (a.pn), middle, and posterior
(p.pn) peduncles of the cerebellum : the anterior connect
it with the testes, and so bound the valve of Vieussens
laterally ; the middle are continuous on each side with the
pons Varolii ; and the posterior connect it to the dorsal
side of the medulla oblongata, and are the anterior ends of
the restiform bodies.

525. The arbor vitae, or tree-like appearance produced
in a section of the cerebellum by the intermixture of its grey
and white matter.

LXIII. Pass a guarded bristle from the fourth ventricle
through the aperture beneath the valve of Vieussens
(§ 523)> and cut down upon it by removing the
optic lobes, so as to expose :

526. The aqueduct of Sylvius (Fig. 72), or iter a
tertio ad quartum ventriculum, a narrow passage by
which the third and fourth ventricles are put in communica-
tion with one another. It is bounded above by the optic
lobes, below by the crura cerebri.

527. Note at the same time the absence of optic ven-
tricles or cavities in the optic lobes.

37$ ZOOTOMY.

p

LX1V. Cut tnrough the three commissures of the
third ventricle, and press the thalami gently apart.
Note :

528. The infundibulum (/"#/), a funnel-shaped cavity
into which the third ventricle is continued below, and
which, after the removal of the pituitary body, opens by
the small aperture already noticed on the base of the brain
(see § 485).

0.1*

j,. a,co. 7 /L

off L& zr

FIG. 72.— Lepus cuniculus. Longitudinal vertical section cf the
brain (nat. size).

a. co, anterior commissure : p.fo, anterior pillar of fornix, supposed
to be seen through optic thalamus : b.fo, body cf fornix : cb, cerebellum,
showing arbor vitoe : c.c, crus cerebri : c.h\y cerebral hemisphere : c.h',
its temporal lobe : c,ma, corpus niammillare : cp.cl, corpus callosum :
f.m, foramen of Monro : in/, infundibulum : ly, lyra : m.co, middle
commissure : m.o, medulla oblongata : o.ch, optic chiasma : o.l1, natis :
o.P, testis : off, olfactory lobe : p.co, posterior commissure : pn, pineal
body : pd.pn, its peduncle : pty, pituitary body : sp.lu, septum lucidum :
vl.ip, velum interpositum : v.vn, valve of Vieussens : ^.4, fourth
ventricle : //, optic nerve.

529. The lamina terminalis, or lamina cinerea (/./),
the thin vertical anterior wall of the third ventricle.

530. By carefully scraping away the inner surface of one
of the optic thalami, trace the anterior pillar of the
fornix (p.fo), which, after curving over the foramen of

THE RABBIT. 379

Monro (§§ 501, 507, 513), passes downwards and back-
wards, and ends in the corpus mammillare : it is best made
out in a fresh brain.

LXV. In another brain make a longitudinal vertical
section of the whole organ, a very little to one
side — say the left — of the median line. Make
out, without further dissection, the relation of the
median ventricles, infundibulum, corpus callosum,
commissures of the third ventricle, &c.
LXVI. In a third thoroughly hardened brain make
a series of transverse sections, and note in them
the relations of the parts already seen by dissec-
tion. The sections should be taken through—
(/?). The anterior end of the corpus callosum and the
septum lucidum.
The anterior commissure.
The foramen of Monro and optic chiasma.
(//). The middle commissure.
(e). The posterior commissure and infundibulum.
(/"). The nates and corpus mammillare.
(g). The testes, valve of Vieussens, and pons Varolii.
(//). The flocculi and hinder part of the medulla
oblongata.

WORKS OF REFERENCE.

The following list makes no pretence to be a complete bibliography,
but simply aims at giving the names of a few books and papers which
students may consult with advantage.

The works marked with an asterisk were published after the
corre; ponding sections of this book were written.

1. BRONN, H. G. Die Klassen und Ordnungen de-; Thier-reichs :
VI. Band (Vertebrata). Leipzig and Heidelberg, 1873 and onwards.

The volume on the Amphibia is the only cne completed, the others are still coming
out in parts.

2. BRUHL, C. B. Zootomie aller Thier Klassen. Vienna, 1875 and
onwards.

Incomplete : contains many good figures illustrating vertehrate anatomy.

3. CHAUVEAU, A. L'Anatomie compareedes Animaux dornestiques.
Paris, 1883 (New Edition).

Contains a good dea.1 of information on the Anatomy of the Rabhit (omitted in
the English edition.)

4. EWART, J. C. On Vaccular PeribrancHr.l Spaces in the Lamprey.
Journal of Anatomy and Physiology, Vol. xii. , 1878, p. 232.

5. EWART, J. C. Notes on the Abdominal Pores and Urogenital
Sinus of the Lamprey. Ib., Vol. x., 1876, p. 488.

6. GEGENBAUR, C. Das Kopfskelet der Selachia. Leipzig,
1872.

7. GEGENBAUR, C. Untersuch. zur vergleich. Anatomic der
\Yirbelthiere, I Heft, Carpus und Tarsus. Leipzig, 1864.

8. GIACOMINI. Method of Preparing the Brain, described in the
Journ. of Anat. and Phys. Vol. xiii., 1879, p. 282.

382 WORKS OF REFERENCE.

9. GUNTHER, A. An Introduction to the Study of Fishes. Edin-
burgh, 1880.

10. HASWELL, W. A. Notes on the Anatomy of Birds. Pro-
ceedings of the Linnean Society of New South Wales. Vol. iv.,
1879, P- 303.

11. HASWELL, W. A. Some Points in the Myobgy of the
Common Pigeon. Journ. of Anat. and Phys. Vol. xvii., 1883,
p. 218.

12. -*Ho\VES, G. B. The Presence of a Tympanum in the Genus
Raia. Journ. of Anat. and Phys. Vol. xvii., 1883, p. iSS.

13. HUXLEY, T. H. A Manual of the Anatomy of Vertebrated
Animals. London, 1871.

Contains a short account of the anatomy of the Rabbit.

14. HUXLEY, T. H. The Nature of the Craniofacial Appar-
atus of Petromyzon. Journal of Anatomy and Physiology, Vol. x.,
1876, p. 412.

15. HUXLEY, T. H. On the Respiratory Organs of Apteryx.
Proc. Zool. Soc., 1882, p. 560.

Contains an account of the general disposition of these organs in birds.

16. HYRTL, J. Das arterielle Gefass system der Rochen. Wien.
Sitz. Ber. xxv., 1857, and Wien. Denkschr. xv., 1858.

17. JoURDAiN, S. Sur la Veine poste re'nale. Annales des Sciences
Naturelles, Zool., Ser. iv., torn, xii., 1859.

1 8. KLEIN, E. The Organ of Jacobson in the Rabbit. Quart.
Journ. of Micros. Science, Vol. xxi., iSSi, p. 549.

19. KRAUSE, W. Die Anatomic des Kaninchens. Leipzig, 1868.

20. MILNE-EDWARDS, H. Lecons sur la Physiologic et 1' Anatomic
compare'e. Paris, 1857-79.

21. MULLER, JOHANNES. Vergleich. Anatomic der Myxinoiden.
Berlin, 1840.

22. MONRO, A. The Structure and Physiology of Fishes. Edinburgh,

1785.
Contains several excellent plates illustrating the anatomy of the Skate.

23. OWEN, R. On the Anatomy of Vertebrata. London, 1866-
1868.

24. PARKER, T. J. On the Intestinal Spiral Valve in the Genus
Raia. Transactions of the Zoological Society, Vol. xi., iSSo, p. 49.

25. PARKER, T. J. On the Venous System of the Skate. Trans-
actions of the N. Z. Institute, Vol. xiii., 1880, p. 413.

WORKS OF REFERENCE. 383

26. PARKER, T. J. On a New Method of preparing Cartilaginous
Skeletons and other Soft Animal Structures. Ib., Vol. xiv., p. 258.

27. *PARKER, W. K. On the Structure and Development of the
Skull in Marsipobranch Fishes. Phil. Trans., 1883, p. 40.

28. PARKER, \V. K. On the Structure and Development of the
Skull of Sharks and Skates. Trans. Zool. Soc., Vol. x., 1878, p.
189.

29. PARKER, W. K. On the Structure and Development of the
Skull in the Lacertilia. Phil. Trans., Part 2, 1879, p. 595.

30. PARKER, W. K., and G. T. BETTAXY. The Morphology of
the Skull. London, 1871.

31. PARKER, W. N. Note on some Points in the Anatomy of the
Caecum in the Rabbit and Hare. Proc. Zool. Soc., 1881, p. 624.

32. ROLLESTOX, G. Forms of Animal Life. Oxford, 1870.

Includes a description of the vertebral column of the Rabb'.t, and of both the
skeleton and soft parts of the Pigeon.

33. STANNIUS, H. Handbuch der Anatomic der Wirbelthiere.
Berlin, 1854.

34. *WIEDERSHEIM, R. Lehrbuch der vergleichenden Anatomic
der Wirbelthiere. Jena, 1883.

INDEX.

C C

INDEX.

A.

ABDOMINAL pore : — Lamprey, 16 ; Skate,

43-

Acetabulum, see Hip-g.rdle.
Acrornion, see Shoulder-girdle.
Adrenal or supra-renal capsule: — Skate,

60 ; Pigeon, 231 ; Rabbit, 300, 302.
Air-bladder: — Cod, 109, 115.
Air-sacs: — Pigeon, 216, 218, 219, 243, 246.
inflation of, 214.
injection of, 214, note.
Al'mentary canal: — Lamprey, 14, 18;
Skate, 47; Cod, in; Lizard, 163;
Pigeon. 226 ; Rabbit, 304.
Ala spuria : — Pigeon, 212.
Alisphenoid : — Cod, 94; Pigeon, 191;

Rabbit, 270.

Angular bone, see Mandible.
Anterior vertebral plate : — Skate, 29.
AnticLnal vertebra : — Rabbit, 265.
Antorbital cartilage : — Skate, 37.
Anus, see External characters.
Aorta, arch of: — Lizard, 172; Pigeon,

238, 240, 243; Rabbit, 311, 327.
dorsal: — Lamprey, 16, 21 ; Skate, 60,
67; Cod, 115; Lizard, 164, 173 ;
Pigeon, 234; Rabbit, 299, 306, 311,

327-
ventral: — Lamprey, 21; Skate, 61 ;

C<?<f, 1 1 6.

Appendix vermiformis : — Rabbit, 298, 305.
Ajjteria or Featherless spaces : — Pigeon,

211.

Aqueduct of Sylvius: — Lamprey, 23;

Skate, 73; Cod, 129; Lizard, 180;

Pigeon, 260 ; Rabbit, 377.
Aqueductus vestibuli : — Skate, 35, 81.
Aqueous humour, j^ Eye.
Arachnoid fluid : — Skate, 46 ; CW, no.

Arbor vitae of cerebellum : — Pigeon, 261 ;

Rabbit, 377.
Artery —

basilar : — Rabbit, 365.

brachial : — Skate, 67; Lizard, 174;

Pigeon, 237; Rabbit, 312.
branchial (afferent and efferent) : —
Lamprey, 21, 22 ; Skate, 61, 66, 69 ;
CVwf, 118, 121.
coronary: — Skate, 61 ; Rabbit, 308,

327-

carotid (common, external, and inter-
nal):— Skate, 68 ; Cod, 121 ; Lizard,
173 ; Pigeon, 237, 239 ; Rabbit, 312.

caudal : — Lamprey, 17 ; Skate, 67 ;
Pigeon, 235.

cerebral (anterior, middle, and pos-
terior):— Rabbit, 365.

cceliac: — Skate, 50, 67; C0</, 113;
Lizard, 164 ; Pigeon, 225, 235 ;
Rabbit, 299.

coeliaco-mesenteric : — Lizard, 164.

duodenal: — Skate, 49 ; Lizard, 164;
Rabbit, 303.

epibranchial : — CV*/, 119.

epigastric : — Rabbit, 315.

femoral: — Lizard, 170; Pigeon, 234;
Rabbit, 315.

gastric: — Skate, 50; Pigeon, 225;
Rabbit, 303.

gastro-duodenal : — Pigeon, 225.

gastro-hepatic : — Skate, 50; Lizard,
164.

hepatic: — Skate, 50; Lizard, 165;
Rabbit, 303.

hyoidean : — Skate, 68; (?<?</, 121.

hypobranchial : — Skate, 61.

iliac (common, external, and internal) :
— Pigeon, 235: Rabbit, 311, 315.

ilio-lumbar : — Rabbit, 315.

C C 2

383

INDEX.

Arter>r (continued') —

innominate : — Skate, 61 ; Pigeon, 237 ;

Rabbit, 312.
lumbar: — Rabbit, 314.
mammary : — Pigeon, 238 ; Rabbit, 314.
mesenteric (anterior or superior, and

posterior or inferior): — Skate, 49,

51, 67; Cod, 113: Lizard, 165;

Pigeon, 226, 235 ; Rabbit, 299, 300.
ophthalmic: — Cod, 175.
pectoral: — Pigeon, 237.
phrenic : — Rabbit, 314.
pulmonary: — Lizard, 172, 173;

Pigeon, 238, 240, 243 ; Rabbit, 308,

325, 328.
renal: — Skate, 67; Pigeon, 235;

Rabbit, 314.

sacral, median : — Rabbit, 314.
sciatic: — Pigeon, 234.
spermatic: — Skate, 67; Rabbit, 314.
splenic :— A* abb it, 303.
subclavian : — Skate, 67 ; Lizard, 174 ;

Pigeon, 237 ; Rabbit, 312, 314.
thoracic : — Rabbit, 314.
vertebral: — Skate, 68; Pigeon, 239;

Rabbit, 314.

Articular bone, stv Mandible.
Articulations —

elbow: — Rabbit, 351.
knee: — Rabbit, 364.
shoulder: — Rabbit, 351.
thigh: — Rabbit, 364.
vertebrae: — Skate. 32, 33; C0</, 88;
Lizard, 132; Pigeon, 186; Rabbit,
267.

Arytenoid cartilage, j^? Larynx.
Atlas vertebra: — Cf</, 89; Lizard, 133;

Pigeon, 186 ; Rabbit, 267.
Auditory capsule : — Lamprey, 5 ; Skate,
34 ; Cfrf, 93 ; Lizard, 136 ; Pigeon,
193 ; Rabbit (periotic), 272.
meatus, external :— Rabbit, 331.

internal, j^t' under Foramen,
organ: — Lamprey, 25; Skate, 80;

CW, 122 ; Pigeon, 193.
ossicles : — Rabbit, 277.
Auricle, s^ Heart.

Axis vertebra '.—Lizard, 133; Pigeon,
185 ; Rabbit, 267.

B.

BARBULE:— CW. 102.

Basal cartilage of fins : — Skate, 33. _

Basale metapterygii or basipterygium : — •

Skate, 40.

Basi-branchial. ^<? Branchial arches.
Basi-hyal, st'*? Hycid.
Basi-occipital: — CW, 91; Lizard, 140;

Pigeon, 190, 192 ; Rabbit, 269.
Basi-pterygoid processes: — Lizard, 141;

Pigeon, 192.

Basi-sphenoid : — Lizard, 141; Pigeon,

192 ; Rabbit, 270.
Basi-temporal: — Pigeon, 192.
Bile ducts (hepatic, cystic, and common
bile durts): — Lamprey, 16 ; Skate, 49,
50; C0^, 112, 113; Lizard, 165, 170;
Pigeon, 223, 224 ; Rabbit, 303.
Bladder, gall: — Skate, 49; CW, 108 ;

Lizard, 161 ; Rabbit, 296.
urinary: — Skate, 58; C<?<f, 109;
Lizard, 168, 171 ; Rabbit, 292, 320,

323-

Body cavity, j^ Coelome.
Brachial ossicles : — tVrt', 101.

plexus, .sw under Nerve plexus.
Brain, removal of : — Lamprey, 23; Skate,
46; C0*/, no ; Lizard, 176 ; Pigeon,
221 ; Rabbit, 294.

dissection of : — Lamprey, 23; Skate,
70; C0</, 123; Lizard, 176; Pigeon,
254; Rabbit, 365.
Branchial apertures, external, se'<? External

characters.

internal, .sr*? Mouth cavity,
arches : — Skate, 38, 66, 68 ; C<?</, 98,
121 ; Lizard, 146; Pigeon, 198;
Rabbit, 276.
basket: — Lamprey, 7.
filaments, $£<? Gills,
rays : — Skate, 69.
Branchiostegal membrane : — CVdT. 103.

rays: — C^t/, 98.
Broad ligament: — Lizard, 168 ; Rabbit,

322.
Bronchi: — Lizard, 175; Pigeon, 220, 244,

245 ; Rabbit, 308, 325.
Bulbus arteriosus, s^ Heart.
Bulla tympani : — Rabbit, 272.
Bursa Fabricii : — Pigeon, 235, 236.

C.

CAECUM coli: — Lizard, 164 ; Pigeon, 223;
Rabbit, 292, 304, 306.

nasal : — Lamprey, 25.

oral: — Lamprey, 20.
Calamus scriptorius : — Skate, 72; Rabbit,

377-

Campanula Halleri : — C<?</, 122.
Capitular facet, ,y<?£ Vertebra.
Carpus, Jt-^ Manus, skeleton of.
Cartilages of skull : — Lamprey, 6, 7.
Centrum, j^ Vertebra.
Cerato-branchial, s^ Branchial arches.
Cerato-hyal, j^ Hyoid.
Cere: — Pigeon, 209.

Cerebellum: — Lamprey, 23; Skate, 70;
Ctfrt', 124 ; Lizard, 178 ; Pigeon, 256,
258 ; Rabbit, 366.
peduncles of: — Rabbit, 367, 377.
Cerebral hemispheres: — Lamprey, 24;

CW, 124; Lizard, 178; Pigeon, 256;

Rabbit, 368.

Circle of Willis :— Rabbit. 365.
Circulus cephalicus : — Cod, 121.
Chevron bones : — Lizard, 134.
Chondrocranium : — Lizard, 143.
Chorda tympani : — Skate, So.
Choroid, see Eye.

processes, see Eye.

gland: — Cod, 122.

plexus: — Lizard, 180 ; Pigeon, 259;

Rabbit, 373.
Claspers : — Skate, 41.
gland of, 60.
skeleton of, 40.
Clavicle, see Shoulder-girdle.
Cloaca:— Skate, 44, 47 ; Lizard, 168, 170 ;

Pigeon, 223, 235.

Ccelome (including abdominal and thoracic
cavities): — Lamprey, 13; Skate, 43;
Cod, 107; Lizard, 159; Pigeon, 216 ;
Rabbit, 291, 293.

Colon :—Skate, 47 ; Rabbit, 292, 304.
Columella or Epipterygoid : — Lizard,

142.
auris : — Lizard, 137, 142; Pigeon,

i95. 25i-

Commissures of brain (anterior, middle,
and posterior): — Lizard, 181 ; Pigeon,
260 ; Rabbit, 375, 376.
Conus arteriosus, .ur Heart.
Coracoid, st'£ Shoulder-girdle.
Cornea, ^^ Eye.
Coronary bone, see Mandible.

ligament: — Cod, 112 ; Rabbit, 296.
Corpus or Corpora —

adiposa: — Lizard, 161.

bigemina, see Optic lobes.

callosum : — Rabbit, 368, 372, 373.

cavernosa, see Penis and clitoris.

geniculatum : — Rabbit, 376.

mamrmllare : — Rabbit, 369.

quadrigemina, see Oplic lobes.

restiformia, see Medulla obi' ngata.

spongiosum, see Penis and clitoris.

striata : — Lizard, 180; Pigeon, 258;

Rabbit, 373.

Cowper's glands : — Rabbit, 320, 323.
Cranial fossae, see under Fossa:;.
Cribriform plate : — Rabbit, 273.
Crop : — Pigeon, 214, 215.
Crura cerebri : — Skate, 72; Lizard, 178;

Pigeon, 256 ; Rabbit, 368.
Crystalline lens, see Eye.
Cystic duct, see Bile duct.

D.

DEMIBRANCHIA or Half-gill: — Lamprey,

18; Skate, 46.
Dentary, see Mandible.
Diaphragm: — Rabbit, 292, 306.
Ductus arteriosus: — Rabbit, 311.
Cuvierii, see Vein, precavaL

INDEX. 389

Duodenum: — Skate, 47; Lizard, 164;

Pigeon, 220, 226 ; Rabbit, 297, 304.
Dura mater: — Skate, 46 ; Rabbit, 295.

E.

EPEXCEPHALON, see Cerebellum.
Epididymis : — Skate, 56 ; Lizard, 165 ;

Rabbit, 318.

Epibranchial, see Branchial arches.
Epiglottis: — Rabbit, 333.
Epihyal, see Hyoid.
Epiotic: — Cod, 93 ; Lizard, 140; Pigeon,

194.

Epiphyses of vertebrae : — Rabbit, 264.
Epipterygoid or Columella : — Lizard, 142.
Ethmo-turbinal, see Turbinal.
Eustachian tube or recess : — Lizard, 176;
Pigeon, 192, 250; Rabbit, 272, 332,

336.

valve, see Heart, dissection of.
Eye, sec Exiernal characters.

dissection of: — Skate, 84; Cod, 122;

Pigeon, 250 ; Raibit, 330.
Eyelids, see External characters.
Exoccipital : — Cod, 91 ; Lizard, 140 ;

Pigeon, 190 ; Rabbit, 269.
External characters : — Lamprey, 8 ; Skate,
40 ; Cod, 1 01 ; Lizard, 153 ; Pigeon,
2cg ; Rabbit, 286.

F.

FALCIFORM ligament: — Pigeon, 219,- 222.
Fallopian tube : — Skate, 57 ; Rabbit, 322,

324-

Falx cerebri: — Rabbit, 295.
Fascia, dono-lumbar : — Rabbit, 339.

lata : — Rabbit, 354.
Feathers, structure of: — Pigeon, 213.

arrangement of: — Pigeon, 211.
Femoro-tibial or semilunar cartilages: —

Lizard, 152 ; Rabbit, 285.
Femur: — Lizard, 151 ; Pigeon, 206; Rab-
bit, 283.
Fenestra ovalis and rotunda: — Lizard,

142; Pigeon, 195; Rabbit, 272.
Fibula: — Lizard, 152 ; Pigeon, 208 ; A"rt<5-

/>//", 285.

Filoplume : — Pigeon, 209, 214.
Fins, j££? External characters.

skeleton of (fin-rays, &c.) : — Lamprey,

4 ; Skate, 33, 39. 40 ; Ccraf, 88, 101.
Fissure of Bichat : — Rabbit, 374.
Fontanelles, cranial : — Skate, 36; Lizard,

138.
Foramen cordiforme : — Lizard, 150.

magnum : — Skate, 34 ; CVv/, 91 ; Z/2-
«>vz', 136; Pigeon, 190; Rabbit,
268.

390

INDEX.

Foramen (continued1} —

of Monro : — Lizard, 180, 181 ; Pigeon,

259; Rabbit, 373.
obturator, see Hip-girdle,
olfactory : — Skate, 30 ; Lizard, 144 ;

Pigeon, 191 ; Rabbit, 273.
optic: — Skate, 30 ; Pigeon, 192; Rab-
bit, 271.

for 3rd nerve : — Skate, 36.
for dth nerve : — Skate, 36.
for 3rd, 4th, first division of 5th and
6th nerves (sphenoidal fissure): — •
Rabbit, 271.
for 3rd division of sth nerve (foramen

lacerum): — Rabbit, 273, 276.
for 5th nerve : — Pigeon, 194.
for 5th and 7th nerves : — Skate, 35 ;

Cod, 93 ; Lizard, 143.
for 7th nerve: — Pigeon^ 194; Rabbit,

272.

for Sth nerve (internal auditory mea-
tus): — Lamprey, 5; Skate, 36;
Pigeon, 194 ; Rabbit, 272.
for gth and loth nerves : — Skate, 35 ;

Cod, 91.

for gth, loth, and nth nerves (foramen
lacerum posterius) : — Lizard, 142 ;
Pigeon, 194 ; Rabbit, 273.
for i2th nerve (condyloid foramen): —

Pigeon, 194 ; Rabbit, 269.
Fore limb, see External characters.

skeleton of: — Skate, 39 ; Cod, 101 ;
Lizard, 147 ; Pigeon, 201 ; Rabbit,
280.
Fornix : — Rabbit, 374, 375, 378.

of Gottsche : — Cod, 128.
Fossa ovalis, sec Heart, dissection cf.
Fossa? of skull : — Lizard, 136, 137 ; Pigeon,

193 ; Rabbit, 268, 276.
Frontal bone : — Cod, 94 ; Lizard, 138 ;

Pigeon, 190 ; Rabbit, 270.
Fronto-nasal process : — Skate, 42.
Furcula : — Pigeon, 201.

G.

GALL-BLADDER, see -under Bladder.

Ganglion, cceliac: — Rabbit, 299.

sympathetic : — Skate, 65 ; Rabbit,
312.

Genital aperture, see External characters.

Gills: — Lamprey, 17; Skate, 45, 60, 69;
Cod, 103, 120, 121.

Gill-rakers : — Cod, 120.

Gizzard: — Pigeon, 220, 227.

Gleno.d cavity, facet, or surface, sec
Shoulder-girdle, Squamosal, and Quad-
rate.

GljttiS, see Mouth cavity.

Gubernaculum : — Rabbit, 318.

Gullet: — Lamprey, 16,18,20; Skate, 47 ;
Cod, 109, in ; Lizard, 175; Pigeon,
215, 217, 243 ; Rabbit, 296, 306, 311.

H.

H.'EMAL arch, process, and spine, see

Vertebra.

Half-gill, see Demibranchia.
Hallux, see Pes.
Hard palate : — Lamprey, 4.
Harderian gland : — Pigeon, 249 ; Rabbit,

33°-

Head-kidney (so-called): — Cod, 115.
Heart : — Lamprey, 20 ; Skate, 45 ; Cod,
no ; Lizard, 162, 171 ; Pigeon,
220, 237 ; Rabbit, 233, 308.
dissection of: — Lamprey, 22 ; Skate,
64 ; Cod, 118 ; Lizard, 174 ; Pigeon,
241 ; Rabbit, 326.
Hepatic duct, see Bile duct.
Hind limb^ see External characters.

skeleton of: — Skate, 40; Cod, 101 ;
Lizard, 150 ; Pigeon, 205; Rabbit,
.283.

Hip-girdle or Pelvis: — Skate, 39; Cod,
101 ; Lizard, 150 ; Pigeon, 204 ; Rabbit,
282.

Hippocampal sulcus : — Rabbit, 375.
Hippocampus major: — Rabbit, 372.
Humerus: — Lizard, 148; Pigeon, 202;

Rabbit, 280.

Hyoid arch or bone: — Skate, 37; Cod,
97 ; Lizard, 145 ; Pigeon, 198 ; Rabbit,
276.

Hyomandibular : — Skate, 37 ; CW. 95.
Hypobranchial, .sr^ Branchial arches.
Hypohyal, see Hyoid arch.
Hypural: — Cod, 90-

I.

I LEO-COLIC valve : — Rabbit, 306.

lleum: — Lizard, 164; Pigeon^ 220, 226;

Rabbit, 297, 304.
Ilium, see Hip-girdle.
Incus: — Rabbit, 277.
Infundibulum : — Skate, 72 ; Lizard, 178 ;

Pigeon, 256; Rabbit, 369, 378.
Injection of vascular system : — Skate /and

General Directions), 48 ; CW, in, note ;

Lizard, 162, note; Pigeon, 218, note;

Rabbit, 298, «<?&.'.
Innominate bone, ,sr<? Hip-girdle.
Integument, see External characters.
Inter-clavicle, see Shoulder-girdle (Liz-
ard).

Inter-hyal, see Hyoid (Lizard).
Inter-muscular bones : — Cod, go.
Inter-neural plates: — Skate, 32.
Inter-opercular, see Operculum.
Inter-crbital septum: — Lizard, 137, 143;

Pigeon, 191.

Inter-parietal: — Rabbit, 270.
Inter-renal body ; — Skate. 59.
Inter-spin^us bones : — Cod, 90.

INDEX.

Inter- vertebral foramina, see Vertebra,
ligament: — Rabbit, 267.
substance: — Skate, 33.
Intestine : — Lamprey, 14 ; Skate, 44, 47 ;
Cod, 107, in ; Lizard, 161, 164;
Pigeon, 220, 223, 226 ; Rabbit, 292,

3°4. 3°5-

Intra-colic valve : — Rabbit, 306.
Ischium, see Hip-girdle.

J-

JACOBSON'S organ and cartilage: — Liz-
ard, 176 ; Rabbit, 273, 336.

Jejunum : — Pigeon, 226.

Jugal or Malar: — Lizard, 138; Pigeon,
197 ; Rabbit, 274.

K.

Kidneys: — Lamprey, 15 ; Skate, 54 ; Cod,
116 ; Lizard, 169 ; Pigeon, 229 : Rabbit,
299, 302, 314, 324.

L.

LABIA majora: — Rabbit, 321.
Labial cartilages: — Skate, 36.
Lacrymal bone : — CW, 100 ; Lizard, 139;
Pigeon, 196 ; Rabbit, 275.

gland: — Pigeon, 249; Rabbit, 330.
Lacteals : — Rabbit, 304.
Lamina perpendicularis : — Rabbit, 273.

terminalis. Pigeon, 258 ; Rabbit, 378.
Larynx : — Lizard, 175 ; Pigeon, 248 ;
Rabbit, 289, 313.

dissection of: — Rabbit, 336.
Lateral line : — C0*/, 102.
Ligamentum suspensorium : — Pigeon, 186.
Ligaments, j^ Articulations.
Limbs, .Ktf Fore limb and Hind limb.
Linea alba : — Rabbit, 291.
Liver: — Lamprey, 13; Skate, 44; CW,
107; Lizard, 159; Pigeon, 220, 223;
Rabbit, 292, 296.
Lobi inferiores : — Skate, 72; C<?*/, 124.

posteriores : — C«^, 128.
Lower jaw, .sw Mandible.
Lungs : — Lizard. 162, 168, 175 ; Pigeon,

221, 244-246 ; Rabbit, 294, 325.
Lymphatic gland : — Pigeon, 240.
Lymph-sinus, sub-vertebral : — Lamprey,

15-
Lyra : — Rabbit, 372.

M.

MALLEUS : — Rabbit, 277.
Mammary glands : — Rabbit, 289.
Mandible or Lower jaw : — Skate, 37 ; Cod,

97 ; Lizard, 145; Pigeon, 197 ; Rabbit,

276.

Manubrium, j^c Sternum.
Manus, s^ External characters.

skeleton of: — Lizard, 149; Pigeon,

202 ; Rabbit, 281.
Maxilla: — CW, 96; Lizard, 138; Pigeon,

196 ; Rabbit, 274.

Maxillo-palatine process: — Pigeon, 196.
Meckel's cartilage : — Skate, 37 ; CW, 97 ;

Lizard, 145 ; Pigeon, 198.
Mediastinum : — Rabbit, 294, 307.
Medulla oblongata : — Lamprey, 23 ; Skate,

70;

123; Lizard, 176; Pigeon,

254 ; Rabbit, 366.
Membranous labyrinth, .rc'e' Auditory

organ.

Membrana semilunaris : — Pigeon, 246.
Meniscus of jaw : — Rabbit, 276.
of vertebrae : — Pigeon, 186.
Mesencephalon, s^ Mid-brain.
Mesenteric bands : — Lamprey, 15.
Mesentery: — C^, 112; Lizard, 164;

Pigeon, 223 ; Rabbit, 297.
Mesethmoid: — C<?^, 94; Lizard, 143;

Pigeon, 191, 197 ; Rabbit, 273, 336.
Mesoarium : — Lamprey, 14; Skate, 54;
*Cod, 112 ; Lizard, 168.
Mesoccele, j^ under Ventricles of brain.
Mesogaster : — Skate, 47; CW, 112; Zz's-

rtT-rt', 164 ; Pigeon, 223 ; Rabbit, 297.
Mesohepar: — Lizard, 164.
Mesopterygium : — Skate, 39.
Mesopterygoid : — C<?<^, 96.
Mesorchium : — Lamprey, 14; Skate, 54;

C<?rf, 112 ; Lizard, 166 ; Rabbit, 319.
Mesorectum : — Skate, 47; CV**/, 112 ; Z/'s-

<7>v/, 164; Pigeon, 223; Rabbit, 297.
Metacarpus, str Manus, skeleton of.
Metapterygoid : — CW, 96.
Metatarsus, s^ Pes, skeleton of.
Mid-brain or Mesencephalon, s<><? Optic

lobes.
Mouth, aperture of, see External cha-

racters.

cavity of: — Lamprey, 20 ; Skate, 65 ;
Cod, 102 ; Lizard, 175 ; Pigeon,
248 ; Rabbit, 333.

Mtillerian duct, see Pronephric duct.
Muscles of eye : — Skate, 77; Pigeon, 249;

Rabbit, 329.
of fore limb : — Pigeon, 251 ; Rabbit,

339-
of hind limb : — Pigeon, 252 ; Rabbit,

35i-

of larynx : — Rabbit, 337.
of trunk: — Lamprey, n, 13 ;

106 Lizard 16 Pieon

106 ;
Rabbit, 291

of trunk: — Lamprey, n, 13 ; C<?*/,
; Lizard, 156; Pigeon, 215;
bbit 21.

j\. u-vi/it., ^yL.

Muscles —

abductor brachii inferior : — Rabbit,

344-..

brachii superior : — Rabbit, 343.
minimi digiti : — Rabbit, 350.
pollicis : — Rabbit, 348.

392

INDEX.

Muscles (continued) —

brevis: — Rabbit, 358.

longus : — Rabbit, 357,

magnus: — Rabbit, 357.
ambiens : — Pigeon, 254.
anconeus, see triceps,
arytenoid : — Rabbit, 337.
biceps brachii : — Pigeon, 251 ; Rabbit,

.346-

biceps femoris : — Rabbit, 356.
basio-humeralis : — Rabbit, 341.
brachialis interims: — Rabbit, 346.
bursalis : — Pigeon, 249.
cleido-mastoid : — Rabbit, 341.
coraco-brachialis : — Rabbit, 344.
curaco brachialis longus : — Pigeon,

218.

costo-pulmonary : — Pigeon, 244.
cremaster: — Rabbit, 318.
crico-arytenoid : — Rabbit, 337, 338.
crico-thyroid : — Rabbit, 337.
crureus: — Rabbit, 356.
deltoid: — Rabbit, 341.
erector spinae: — Rabbit, 343.
extensor carpi radialis : — Rabbit, 346.

ulnaris : — Rabbit, 348.
communis digitorum (inanus): —

Rabbit^ 46.
communis digitorum (pedis): —

Rabbit, 360.

digiti primi (pedis) : — Rabbit, 360.
hallucis brevis: — Pigeon, 252.
longus digitorum (pedis): — Pigeon,

252.

metacarpi radialis longus : — Pi-
geon, 251.

parvusantibrachii : — Rabbit. 345.
pollicis et indicia : — Rabbit, 348.
quarti digili : — Rabbit, 348.
quinti dig.ti : — Rabbit, 348.
flexor brevis minimi digiti: — Rabbit,

35°;

pollicis: — Rabbit, 350.
carpi radialis: — Rabbit, 348.

ulnaris : — Rabbit, 348.
digitorum communis (pedis) :-

Rabbit, 363.
digitorum profundus v. perforans :

— Pigeon, 253 ; Rabbit, 349.
digitorum sublimis v. perforatus :

— Pigeon, 253 ; Rabbit, 349.
gastrocnemius : — Pigeon, 253 ; Rabbit,

360.

gemelli : — Rabbit, 359.
glutei (maximus, msdius, and mini-
mus) : —Rabbit, 358, 359.
gracilis : — Rabbit, 354.
iliacus: — Rabbit, 353, 358.
jnfra-spinatus : — Rabbit, 344.
intercostals : — Lizard, 159; Rabbit,

290.

interossei fmanus) : — Rabbit, 351.
(pedis) -.—Rabbit, 364.

Muscles (continued} —

latissimus dorsi : — Rabbit, 339.
levator anguli scapulae : — Rabbit, 343.

scapulse major: — Rabbit, 341.
lumbricales (maims): — Rabbit, 350.

(pedis): — Rabbit, 363.
masseter : — Rabbit, 329.
mylohyoid : — Lizard, 158.
oblique cf abdomen (external and in-
ternal):— Lizard, 158, 159 ; Pigeon,
216 ; Rabbit, 291.
oblique of eye (superior and inferior) :^-

Skate, 77. 78 ; Rabbit, 329, 330.
obturator (internus and externus): —

Rabbit, 359.
palmarls: — Rabbit, 349.
panmculus carnosus : — Rabbit, 288.
papillary, see Heart, dissection of.
pectinate, see Heart, dissection of.
pectineus : — Rabbit, 358.
pectoralis : — Lizard, 158.

major: — Pigeon, 215, 252 ; Rabbit,
290.

minor: — Rabbit, 290, 343.

secundus, see subclavius.

tenuis : — Rabbit, 290.
peroneus brevis : — Rabbit, 363.

longus : — Rabbit, 363.

medius : — Pigeon, 254.

quarti digiti : — Rabbit, 363.

quinti digiti : — Rabbit, 363.
plantans: — Rabbit, 362.
pcpliteus : — Rabbit, 362.
pronator teres: — Rabbit, 348.
psoas magnus : — Rabbit, 351, 358.

parvus: — Rabbit, 353.
pterygoid : — Rabbit, 332.
pyramidalis: — Pigeon, 249.
pyriformis : — Rnbbit, 359.
quadratus femoris : — Rabbit, 359.

lurnborum : — Rabbit, 353.
quadriceps: — Rabbit, 354.
rectus abdominis: — Lizard, 156; Pi-
geon, 216 ; Rabbit, 291.

anticus : — Rabbit, 354, 356.
recii of eye : — Skate, 77, 78 ; Rabbit,

""* *^C\

jj°-

retractor bulbi : — Rabbit, 330.
of tongue : — Lamprey, 18.
rhomboideus cervioalis : — Rabbit, 342.

dorsaLs : — Rabbit, 342.
sartorius : — Rabbit, 354.
semi-membranosus : — Rabbit, 357.
semi-tendinosus : — Rabbit, 357.
serratus magnus : — Rabbit, 343.
soleus : — Rabbit, 362.
stapedius : — Rabbit, 332.
sterno-mastoid : — Rabbit, 290.
sterno-tracheal : — Pigeon, 221.
subclavius : — Pigeon, 218, 252.
subscapularis : — Rabbit, 344.
supra-spinatus : — Rabbit, 344.
syringeal, intrinsic : — Pigeon, 244.

INDEX.

393

Muscles (continued') —

tensor patagii, longus, brevis, and,
accessorius : — Pigeon, 251, 252.
tympani : — Rabbit, 332.
teres major : — Rabbit, 344.

minor : — Rabbit, 345.
thyro-arytenoid : — Rabbit, 338.
tibialis anticus : — Rabbit, 360.
transversalis abdominis : — Pigeon,2i6 ;

Rabbit, 291.
trapezius : — Rabbit, 339.
triceps: — Pigeon, 251 ; Rabbit, 345.
vastus internus and externus : — Rabbit,

354. 356-

Myelencephalon, see Medulla oblongata.
Myelocoele, see Ventricles of brain, 4th.
Myelon, see Spinal cord.
Myotomes or Myocommas : — Lamprey, 12;
Cod, 1 06.

N.

NARES, anterior, see External characters.

posterior, see Mouth cavity.
Nasal bones : — Cod, 99 ; Lizard, 138,
Pigeon, 197 ; Rabbit, 274.

caecum : — Lamprey, 25.

capsule : — Lamprey, 5 ; Skate, 35 ;
Lizard, 143.

sac, see Olfactory organ.
Naso-buccal groove : — ^>kale, 42.
Naso-palatine canal : — Lamj-rey, 4; Rab-

h'', 335-
Nerves —

ist cerebral (olfactory): — Lamprey,

24 ; Skate, 72, 79 ; Cod, 124; Lizard,
178 ; Pigeon, 256; Rabbit, 336, 368.

2nd cerebral (optic): — Lamprey, 24;
Skate, 73, 78; Cod, 126; Lizard,
i?9 ; Pigeon, 256 ; Rabbit, 330,

369-
3rd cerebral (oculomotor) : — Lamprey,

24; Skate, 74, 77, 78; Cod, 126;

Lizard, 179 ; Pigeon, 256 ; ^Rabbit,

330, 369-
4th cerebral (pathetic) : — Lamprey,

25 ; Skate, 74, 77 ; CW,i26 ; Lizard,
i?9 ; Pigeon, 257 ; Rabbit, 330, 369.

5th cerebral (trigemmal) : — Lamprey,
25 ; Skate, 75-79 ; Cod, 106, 126 ; Liz-
ard, 179; Pigeon} 257; Rabbit, 332,

369-
6th cerebral (abducent) : — Skate, 76,

77 ; CW, 127 ; Lizard, 179 ; Pigeon,

257 ; Rabbit, 330, 369.
7th cerebral (facial or portio dura) : —

Lamprey, 25 ; Skate, 76, £o ; Cod,

122, 126 ; Lizard, 179 ; Pigeon, 257 ;

Rabbit, 329, 370.
8th cerebral (auditory) : — Lamprey,

25 ; Skate,-j6, 82 ; CW, 127 ; Lizard,

*79; Pigeon, 257; Rabbit, 370.

Nerves (continued) —

9th cerebral vglossopharyngeal) :—

Lamprey, 25 ; Skate, 76, 82, 83 ;

CW, 119, 127 ; Lizard, 179 ; Pigeon,

257 ; Rabbit, 332, 370.
loth cerebral (vagus or pneumogas-

tric) : — Lamprey, 25 ; Skate, 51, 76,

81, 83; 6W, 106, 112, 119, 196;

Lizard, 179; Pigeon, 225, 240,257 ;

Rabbit, 299, 311, 313, 332, 370.
nth cerebral (accessory): — Lizard,

*79 5 Pigeon, 257 ; Rabbit, 332, 370.
i2th cerebral (hypoglossal) : — Lizard,

179; Pigeon, 257; Rabbit, 313,

332> 37°-

branchial : — Skate, 82.
circumflex : — Rabbit, 338.
chorda tympani : — Skate, So ; Cod ',126.
crural : — Rabbit, 339.
cutaneous : — Cod, 106, 127.
femoral : — Pigeon, 247.
gustatory : — Rabbit, 332.
hyomandibular : — Skate, 80.
mandibular : — Skate, 79; CW, 126;

Rabbit, 332.
maxillary :— Skate, 79 ; CW, 126 ;

Rabbit, 333.
median : — Rabbit, 338.
musculo-spiral : — Rabbit, 338.
orbito-nasal : — Skate, 76-78; CW, 126;

Rabbit, 330.

obturator : — Pigeon, 247 ; Rabbit, 339.
pakuine: — Skate, 80.
palato-nasal : — Skate, 79; CW, 126.
phrenic: — Rabbit, 311.
sciatic: — Pigeon, 247; Rabbit, 339.
spinal: — Skate, 82, 83; Pigeon, 247.
splanchnic : — Pigeon, 226 ; Rabbit, 299.
subscapular : — Rabbit, 338.
sympathetic: — Skate, 65, 83; CW,

116; Pigeon, 247 ; Rabbit, 312, 313.
ulnar: — Rabbit, 338.
Nerve-plexus —

brachial : — Skate, 82; Pigeon, 247;

Rabbit, 338.
lumbar: — Pigeon, 247.
lumbo-sacral : — Rabbit, 338.
sciatic: — Pigeon, 247.

Neural canal and processes : — Lamprey, 2.
arch, processes, and spine, i-6't' Vertebra.
Neurapophysis, sf£ Vertebra.
Nictitating membrane, j^g External cha-
racters.

Nostrils, j^ External characters.
Notochord : — Lamprey, 2.

O.

OBLIQUE septum : — Pigeon, 226.
Occipital arch : — Lamprey, 5.

bone, £££ Basi-, Ex-, and Supra-occi-
pital.

394

INDEX.

Occipital (coutlnned) —

condyle : — Skate, 34 ; Cod, 91 ; Liz-
ard, 136; Pigeon, 190 ; Rabbit, 268.
foramen, see Foramen magnum.
Odontoid bone or process : — Skate, 29 ;
Lizard, 133; Pigeon, 185; Rabbit,
267.

(Esophagus, see Gullet.
Olfactory foramen, see under Foramen,
lobe: — Lamprey. 24; Skate, 72, 79;
Cod, 124 ; Lizard, 178 ; Pigeon,
256 ; Rabbit, 368.

organ: — Lamprey, 24; Skate, 78, 79;
CTtf^, 122 ; Pigeon, 249 ; Rabbit,

335-

Omentum, duodeno-hepatic : — Skate, 47;
Lizard, 164 ; Pigeon, 222 ; Rabbit,
297.

gastro-hepatic : — Skate, 47 ; CW, 112 ;
Lizard, 164 ; Pigeon, 223 ; Rabbit,
297.
gastro-splenic : — Skate, 47; Rabbit,

297.
great: — Pigeon, 217, 222; Rabbit,

297.

Opercular bones: — CW, 99.
( Jperculum : — C<^, 103.
Ophthalmic peduncle : — Skate, 78.
Opisthotic : — C<?<f, 93; Lizard, 140; /Y-

£zw*, 194-

Optic chiasma and tracts: — Skate, 74;
Lizard, 179 ; Pigeon, 256 ; Rabbit,
369. .376.

commissure : — Pigeon, 258.
foramen, 5^^ -under Foramen,
lobes : — Lamprey, 25 ; Skate, 70-;
6"<?^/, 124 ; Lizard, 178 ; Pigeon,
256 ; Rabbit, 376.

thalami : — Lamprey, 23 ; Skate, 72 ;
Lizard, 180 ; Pigeon, 258 ; Rabbit,

375-

Ora serrata, ££(? Eye, dissection of.
Oral aperture, .j^v External characters,
caecum: — Lamprey, 20.
cavity, s^ Mouth, cavity of.
funnel: — Lamprey, 8, 13.
Orbit '.—Lizard, 135; Pigeon, 190, 191;

Rabbit, 268.

Orbito-sphenoid : — Rabbit, 271.
Os cloacae : — Lizard, 150.

innominatum, s££ Hip-girdle,
orbiculare: — Rabbit, 277.
Ossicula auditus : — Rabbit, 277.
Otoliths or otolithic mass: — Skate, 81 ;

C<?^, 123.

Ovary: — Lamprey, 13; Skate, 54; C^,
108, 114 ; Lizard, 167 ; Pigeon, 229 ;
Rabbit, 322.

Oviducal gland : — Skate, 58.
Oviduct : — Skate, 51, 56, 58 ; C<7£/, 114 ;
Lizard, 168, 171 ; Pigeon, 229, 236.

P.

PALATINE bone: — CW, 96 ; Lizard, 141 ;

Pigeon, 196 ; Rabbit, 275.
foramen: — Lizard, 136.
Pancreas: — Skate, 44; Lizard, 164;

Pigeon, 220 ; Rabbit, 300.
Pancreatic duct: — Skate, 50; Pigeon,

224 ; Rabbit, 300.
Parachordal plate: — Lamprey, 4.
Parasphenoid : — C^, 94; Lizard, 141;

Pigeon, 192.

Parethmoid : — CW, 95 ; Rabbit, 274.
Parietal : — C<?</, 94 ; Lizard, 138 ; Pigeon,

190 ; Rabbit, 270.
Parorchis: — Skate, 56.
Paroiic or paroccipital process : — C^, 93 ;

Lizard, 136.

Parovarium \-Skate, 60.
Patella: — Pigeon, 208 ; Rabbit, 284.
Pecten of eye : — Pigeon, 250.
Pectoral fin, ^^ Fore limb.
Pelvic fin, j^ Hind limb.
Pelvis, tt?^ Hip-girdle.
Penis: — Lizard, 171; Rabbit, 287, 316;

320.
Pericardio-peritoneal canals: — Skate, 64.

septum : — Skate, 45 ; (7<?rf, 109.
Pericardium and pericardial cavity :—

Lamprey, 8, 15, 19 ; Skate, 45 ; C<?<-/,

109, no; Lizard, 162; Pigeon, 220;

Rabbit, 293, 307.
Perineal gland : — Rabbit, 320.
Peritoneum: — Lamprey, 13; Skate, 44,

47 ; CW, 107, 109, 112 ; Lizard, 159 ;

Pigeon, 222 ; Rabbit, 291, 298.
Pes, jtv External characters.

skeleton of: — Lizard, 152 ; Pigeon,

208 ; Rabbit, 285.
Pessulus : — Pigeon, 246.
Peyer's patches : — Rabbit, 305.
Phalanges, ^^ Manus, skeleton of, and

Pes, skeleton of.

Pharyng abranchial, s^ Branchial arch.
Pharynx;— Skate, 65 ; CW, 120; Lizard,

J75 .' Pigeon, 248 ; Rabbit, 333.
Pia mater: — Skate. 46 ; Rabbit, 295.
Pineal body : — Lizard, 178; Pigeon, 256;

Rabbit, 368, 375.
Pituitary body : — Skate, 72 ; Craf, 124 ;

Lizard, 178; Pigeon, 256; Rabbit,

369-
Pleura: — Lizard, 168 ; Pigeon, 244;

Rabbit, 294, 307.
Plexus, .sr*? Nerve-plexus.
Pons Varolii : — Rabbit, 367.
Pori femorales : — Lizard, 156,
Post-clavicle: — CW, 100.
Post-orbital bones : — Lizard, 139.
Post- temporal :• — C0</, 100.
Poupart's ligament: — Rabbit, 291.
Precoracoid : — Lizard, 146.
Pre-frontal : — Lizard, 139.

INDEX.

595

Pre-maxilla : — Cod, 96; Lizard, 138;

Pigeon, 196 ; Rabbit, 274.
Pre-opercular, see Upercular bones.
Pre-pubis : — Lizard, 150.
Prepuce: — Rabbit, 316.
Presphenoid : — Rabbit, 271.
Processus falciformis of eye: — Cod, 122.
Pronephric duct: — Skate, 52, 56.
Prootic : — Cod, 93; Lizard, 140; Pigeon,

194.

Propterygium : — Skate, 39.
Prosencephalon, see Cerebral hemispheres.
Prostate : — Rabbit, 319, 321.
Proventriculus : — Pigeon, 225, 227.
Pseudobranchia : — Skate, 43; Cod, 103,

1 20.

Pterotic : — Cod, 93.
Pterygoid bone:— Cod, 96 ; Lizard, 141 ;

Pigeon, 195 ; Rabbit, 275.
Pterygo-quadrate cartilage : — Skate, 37.
Pterylae, or feather tracts: — Pigeon, 211.
Pterylosis, or feather arrangement •-—

Pigeon, 211.
Pubis, see Hip-girdle.
Pupil, see Eye.
Pygostyle : — Pigeon, 188.
Pylangium, see Heart.
Pylonc cseca : — Cod. 107, 113.
valve, ^^ under Valve.

Q-

QUADRATE: — Cod, 96; Lizard, 136, 140;

Pigeon, 195.
Quadrato-jugal: — Pigeon, 197.

R.

RADIUS: — Lizard, 148; Pigeon, 202;

Rabbit, 280.

Rectal gland : — Skate, 47 ; Rabbit, 320.
Rectrices: — Pigeon, 212.
Rectum : — Lamprey, 14 ; Skate, 47 ; CW,

in ; Lizard, 164 ; Pigeon, 223 ; Rabbit,

292, 305.

Remiges: — Pigeon, 212.
Reproductive organs, «r*? Testis, Ovary,

&c.

Respiratory tube : — Lamprey, 18, 20.
Restiform bodies, s^<? Medulla oblongata.
Rete mirabile of air-bladder : — CW, 115.
Ketina, see Eye.

Rhiner.cephalon, «r Olfactory lobe.
Ribs:— Skate, 32 ; Cod, 90; Lizard, 135 ;

Pigeon, 185, 186; Rabbit, 268.
Rostrum of skull and rostral cartilages: —

Skate, 35.

S.

SACCULUS rotundus : — Rabbit, 304.
Saccus vasculosus : — Skate, 72.
Sacrum, j>w Vertebral column.

Salivary glands : — Rabbit, 289, 313, 329.

sac: — Lamprey, 19.
Scales: — Skate, 41 ; Cod, 101, 102 ; Lizard,

154-

Scapula, see Shoulder-girdle.
Schneiderian membrane, see Olfactory or-
gan.
Sclerotic, see Eye, dissection of.

plates: — Lizard, 176; Pigeon, 250.
Scrotal sacs: — Rabbit, 292, 318.
Sella turcica : — Rabbit, 270.
Semicircular canals, see Auditory organ.
Semilunar fibru-cartilages : — Lizard, 152 ;

Rabbit, 285.

Sensory tubes : — Lamprey, n ; Skate, 43.
Septomaxillary : — Lizard, 145.
Septum lucidum : — Rabbit, 373.

nasi, see Mesethmoid.
Sesamoid bones: — Rabbit, 281, 282, 284,

286.

Shoulder-girdle: — Skate, 38; Cod, 100 ;
Lizard, 146 ; Pigeon, 200 ; Rabbit, 278.
Sinus (venous, lymphatic, &c.) —
cardinal : — Skate, 52.
circum-oesophageal : — Lamprey, 19.
hepatic : — Skate, 51, 65.
peribranchial : — Lamprey, 18.
precaval: — Skate, 65.
rhomboidalis : — Pigeon, 222.
spermatic : — Skate, 52.
venosus, see Heart.

Skeleton, preparation of: — Lamprey, i
Skate, 27 ; Cod, 86 ; Lizard, 130
Pigeon, 182 ; Rabbit, 262.
general characters of: — Skate, 28
CW, 87 ; Lizard, 131 ; Pigeon, 183
Rabbit, 262.

Skull : — Lamprey, 4 ; Skate, 34 ; CW, 91
Lizard, 135 ; Pigeon, 190 ; Rabbit
268.

Specific characters : — Petromyzon, 8, 10
Raja, 41, 42 ; Gadus, 91, 100, 102
Lacerta, 155.

Sperm sacs : — Skate, 56, 59.
Sphenoidal fissure : — Rabbit, 271.
Sphenotic: — C<7^, 93.
Spinal cord: — Lamprey, 23; Skate, 52,

70 ; Pigeon, 222.
Spiracle: — Skate, 43, 65.
Spiracular cartilage: — Skate, 37.
Spiral valve, s^ under Valve.
Spleen :— Skate, 44 ; CW, 108 ; Lizard,

164 ; Pigeon, 225 ; Rabbit, 297.
Splenial, m- Mandible.
Squamosal: — Lizard, 140; Pigeon, 191;

Rabbit, 271.
Stapes:— Lizard, 142; Pigeon, 195;

Rabbit, 277.
Stenson's canal, 5^ Naso-palatine canal.

duct, s£t? Salivary glands.
Sternebrse : — Rabbit, 268.
Sternum -—Lizard, 134; Pigeon, 198;
Rabbit, 268.

396

INDEX.

Stomach: — Skate, 44, 47; Cod, 107, in,
113; Lizard, 163, 170; Pigeon, see
Gizzard and Proventriculus ; Rabbit,
292, 296, 305.

StritE longitudinales: — Rabbit, 372.

Stylo-hyal, see Hyoid.

Sub-ocular arch : — Lamprey, 5.

Sub-opercular, see Opercular bones.

Sub-orbitals : — Cod, 100.

Sub-vertebral wedge bone: — Lizard, 133.

Supra-angular, see Mandible.

Supra-clavicle : — Cod, 100.

Supra-occipital: — Cod, 91; Lizard, 140;
Pigeon, 190 ; Rabbit, 269.

Supra-orbitals : — Lizard, 139.

Supra-renal bodies, see Adrenals.

Supra-scapula, see Shoulder-girdle.

Supra-temporal: — Lizard, 139.

Suspensory ligament : — Rabbit, 296.

Sutures, cranial, see Skull.

Symplectic : — Cod, 95.

Synangium, see Heart.

Synovial cavity : — Pigeon, i£6 ; Rabbit,

35L 364-
Syrinx : — Pigeon, 244-246.

T.

semicircularis : — Rabbit, 374.
Tapetum : — Rabbit, 331.
Tarsus, see Pes, skeleton of.
Tarso-metatarsus : — Pigeon, 208.
Teeth: — Lamprey, 10 ; Skate, 42; Cod,

120 ; Lizard, 175 ; Rabbit, 277, 278.
Tendo Achillis: — Rabbit, 360.
Tentorium cerebelli, or Tentorlal ridge: —

Pigeon, 193 ; Rabbit, 295.
Testis: — Lamprey, 13; Skate, 54; Cod,

108, 113; Lizard, 165; Pigeon, 228;

Rabbit, 318.
Thalamencephalon : — Lamprey, 23 ;Skate,

72; C"<?^, 124; Lizard, 179; Pigeon,

258 ; Rabbit, 375.

Thalami optici, .sv^? Thalamencephalon.
Thalamoccele, j^ Ventricles of brain, 3rd.
Thoracic duct: — Rabbit, 312.
Thymus gland : — Skate, 69; Rabbit, 293.
Thyroid cartilage, s^ Larynx.

gland : — Skate, 64 ; Lizard, 163 ; Rab-
bit, 313.

Tibia : — Lizard, 151 ; Rabbit, 284.
Tibio-tarsus : — Pigeon, 206.
Tongue, •sw Mouth cavity.
Tori semicirculares : — Cod, 128.
Trabeculae : — Lamprey, 4.
Trachea: — Lizard, 162, 175; Pigeon, 215,

220, 244 ; Rabbit, 289, 325.
Trans-palatine or Os transversum : —

Lizard, 141.

Transverse process, see Vertebra.
Trochanter, see Femur.
Trochlea, see Humerus.

Tuberosity, see Humerus and Tibia.

Turbinals : — Lizard, 145 ; Pigeon, 197,
249 ; Rabbit, 274, 275, 335.

Tympanum or tympanic cavity, and tym-
panic membrane : — Lizard, 137, 176 ;
Pigeon, 192, 245, 250 ; Rabbit, 272, 331.

U.

ULNA : — Lizard, 148 ; Pigeon, 202 ; Rab-
bit, 281.

Uncinate processes : — Pigeon, 185.
Ureter : — Lamprey, 15 ; Skate, 59, 60 ;
Cod, \o) ; Lizard, 171 ; Pigeonry., 235 ;
Rabbit, 300, 302, 316, 320, 323.
Urethra -.—Rabbit, 318.
Urinary aperture, see External characters,
bladder, see under Bladder,
papilla : — Skate, 56.

Urinogenital organs, dissection of: — Lam-
prey, 13; Skate, 54; Cod, 113;
Lizard, 165, 171 ; Pigeon, 228 ;
Rabbit, 316.
papilla: — Lamprey, 10, 15; Skate,

58 ; Lizard, 171.

sinus : — Lamprey, 15 ; Skate, 59.
Urohyal, see Hyoid.
Uropygial gland : — Pigeon, 247.
Uterus : — Skate, 56 ; Rabbit, 321, 324.
masculinus : — Rabbit, 319, 321.

V.

VAGINA : — Rabbit, 321, 323.
Valve, or Valves —

of heart, see Heart, dissection of.
ileo-colic : — Lizard, 170 ; Rabbit, 306.
intra-colic : — Rabbit, 306.
pyloric : — Skate, 52 ; Corf, 113 ; Lizard,

170; Pigeon, 227 ; Rabbit, 305.
spiral : — Lamprey, 16 ; Skate, 52 ;

Rabbit (caecum), 306.
of Vieussens : — Rabbit, 377.
Valvulae conniventes : — Lizard, 170 ;

Rabbit, 305.

Vas deferens : — Skate, 56, 59; Cod, 114;
Lizard, 171 ; Pigeon, 228, 236 ; Rabbit,
318, 320.
Vein —

anterior abdominal, see epigastric,
azygos, see cardinal,
brachial : — Skate, 65 ; Pigeon, 238.
cardinal : — Lamprey, 16, 22 ; Skate,
52, 60, 65 ; Cod, 115, 116 ; Lizard,
165; Rabbit, 312.

caudal: — Lamprey, 17; Skate, 67;
Cod, 116; Lizard, 169;- Pigeon,
231.

coccygeo-mesenteric : — Pigeon, 2 25, 23 1 .
coronary : — Rabbit, 327.

INDEX.

397

Vein (continued)—

epigastric : — Skate, 68 ; Lizard, 161 ;

Pigeon, 221, 240 ; Rabbit, 315.
femoral : — Skate, 68 ; Lizard, 169 ;

Pigeon, 231 ; Rabbit, 315.
gastric : — Skate, 50 ; Liztnd, 165 ;

Pigeon, 224.

gastro-duodenal : — Pigeon, 224.
hepatic : — Lamprey, 22 ; Skate, 51 ;

Cod, 113 ; Pigeon, 240 ; Rabbit, 306.
hypogastric, -sw renal portal.
iliac (common, internal, and external) :

— Pigeon, 230; Rabbit, 315.
ilio-hae.norrhoidal : — Skate, 68.
intercostal : — Rabbit, 312.
jugular (external, internal, and in-
ferior):— Lamprey, 21, 22; Skate,

63, 65 ; Cod, 115, 118 ; Lizard, 163 ;

Pigeon, 238, 239 ; Rabbit, 289, 310.
mammary : — Pigeon, 238.
mesenteric (anterior or superior, and

posterior or inferior) : — Skate. 50 ;

Cod, 112; Lizard, 165; Pigeon,

224 ; Rabbit, 300.
pancreatic : — Lizard, 165.
pectoral : — Pigeon, 238.
pelvic : — Lizard, 161, 169 ; Pigeon,

231.
phrenic (anterior and posterior) : —

Rabbit, 307, 311.
portal: — Skate, 49, 50; CW, 112;

Lizard, 165 ; Pigeon, 224 ; Rabbit,

303-

precaval (vena cava superior s. an-
terior) : — CW, 115; Lizard, 163,
172 ; Pigeon, 238, 240 ; Rabbit, 310,
326.

postcaval (vena cava inferior £. pos-

terbr): — Lizard, 162, 168, 169, 172;

Pigeon, 230, 239 ; Rabbit, 298, 306,

311, 326.

pulmonary : — Lizard, 173 ; Pigeon,

240; Rabbit, 308. 325, 327.
renal : — Lizard, 169 ; Pigeon, 233 ;

Rabbit, 314.
afferent : — Pigeon, 234.
efferent : — Pigeon, 233.
portal : — Skate, 67 ; Lizard, 169 ;

Pigeon, 231, 234.

sciatic : — Lizard, 169 ; Pigeon, 234.
spermatic : — CW, 113 ; Rabbit, 314.
splenic : — Lizard, 165.

Vein (continued} —

subclavian : — Rabbit, 310.
vertebral : — Pigeon, 239.
Velum interpositum : — Pigeon, 258 ;

&V. 375-
palati, see Mouth cavity.
Ventricles of heart, see Heart,
larynx, see Larynx,
brain —

3rd : — Lamprey, 23 ; Skate, 72 ;
Cod, 129; Lizard, 181 ; Pigeon
258, 260 ; Rabbit, 375.
4th : — Lamprey, 23 ; Skate, 73 ;
Cod, 128 ; Lizard, 178 ; Pigeon,
254, 260 ; Rabbit, 376.
5th -.—Rabbit, 373. *
lateral : — Lizard, 180 ; Pigeon,

258 ; Rabbit, 372, 374.
olfactory : — Lizard, 180.
optic : — Lamprey, 23 ; Skate, 73 ;
C0t/, 128 ; Lizard, 180 ; Pigeon,
260.

Vertebra, characters of, and Vertebral

columns : — Lamprey, 2 ; Skate, 29 ; C#<f.

88 ; Lizard, 132 ; Pigeon, 183 ; Rabbit,

265.

Vertebrarterial canal : — Pigeon, 185 ; ^va£-

&Y, 266.

Verumontanum : — Rabbit, 321.
Vesicula semmales : — Skate, 59.
Vestibule, jtv Auditory organ.

(female urinogenual canal) : — Rabbit,

321, 323.

Villi : — Pigeon, 227 ; Rabbit, 305.
Vitreous humour, see Eye.
Vocal chords, see Larynx.
Vorner : — Cod, 94 ; Lizard, 141 ; Pigeon,

196 ; Rabbit, 274..
Vulva : — Rabbit, 321.

W.

WING, $££ Fore limb.

X.

XIPHOID process, see Sternum.

Z.

ZYGAPOPHYSES, see Vertebra.

THE END.

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