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THE FUNDUS OCULI OF BIRDS

CASEY ALBERT WOOD

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To
Professor Meynard M. Metcalf ,
With the Compliments of
The Author.

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THE FUNDUS OCULI
OF BIRDS

THE FUNDUS OCULI OF BIRDS
ESPECIALLY AS VIEWED BY THE

OPHTHALMOSCOPE

A Study in
Comparative Anatomy and Physiology

CASEY ALBERT WOOD

Illustrated by 145 drawings in the text; also by sixty-one

colored paintings prepared for this work by

Abthur W. Head, F. Z. S.

London

CHICAGO

THE LAKESIDE PRESS

1917

TABLE OF CONTENTS

CHAPTER PAGE

I. Introduction 5

II. Summary of Conclusions 7

III. Collection, Selection and Preparation of Mate-

rial

Bibliography 8

IV. A Review of the Anatomy and Physiology of the

Organs and Tissues seen in the Fundus Oculi

of the Bird 12

V. Ophthalmoscopy, or the Examination through
the Pupils, in Animate Specimens, of the Inte-
rior of the Vertebrate Eye by Means of the

Ophthalmoscope 26

VI. Ophthalmoscopy of the Fundus in Living Birds: 33

A. The Eye-ground in General 36

B. The Pecten and Optic Disc 38

C. The Macular Regions, Fovese and other Areas

of Acute Vision 38

D. The Fundal Bloodvessels, the Opaque Nerve

Fibres, the Choroid and the Retina . . 38

E. Photography of the Fundus in Living Birds . 44
VII. Macroscopic Appearances of the Fundus Oculi of

Birds in Prepared Specimens 49

Photography of the Fundus in Prepared Eyeballs 61
VIII. Effects of Domestication on the Fundus Oculi

of Wild Species of Birds 62

IX. The Ophthalmoscopic and Macroscopic Appear-
ances of the Fundus Oculi in Various Orders
of Birds.

A. Ratitse 64

B. Carinatse 68

X. Classification of the Ocular Fundi of Birds . 112

XI. The Ocular Fundus of Birds in its Relation to

a Classification of Aves 114

XII. The Relations of Reptilian to Avian Fundi . . 116

XIII. Colored Drawings of the Fundus Oculi of Birds 119

Colored Drawings of the Fundus Oculi of Reptiles . 178

<> 1 ^ 5 .9

Chapter I
INTRODUCTION

Although the ophthalmoscopic and naked-
eye appearances of the fundus oculi have been
thoroughly described and depicted by other
writers in many of the Mammals — espe-
cially in Man — yet very little attention has
been paid to the remarkable and interesting
eyegrounds of the animal that exhibits the
highest and most varied types of vision —
the Bird. The meagre accounts given by
even modern writers of the appearances of
the avian fundus are probably due either to
their quoting the ill-formed opinions of early
observers or to their ignorance of the proper
use of the ophthalmoscope; facility in the
employment of this instrument is acquired
only after long practice, and it is not to be
expected that every zoologist can make his
own notes of fundus pictures.

The main purpose of this study is to furnish
such a description of the intraocular appear-
ances and the methods employed in viewing
them as will enable other ophthalmologists
and zoologists to further this study by ex-
amining the eyegrounds of Birds that come
under their observation.

The eyes of some representative of (prac-
tically) all the Orders of Birds and most of
their backgrounds have been examined by
the writer; and are more or less fully de-
scribed and illustrated in this Atlas. More-
over, some of the more important species
were examined not only ophthalmoscopically
before death but macroscopically afterwards.
In addition to these methods of investigation
extensive microscopic examinations of the
tissues were carried on, especially in conjunc-
tion with Professor J. R. Slonaker.

That this research might have a broader and
more useful application the writer has also ex-

amined the ocular fundi of a number of species
of other vertebrate orders. A brief compari-
son will be made between a few of these find-
ings and those discovered in the avian fundi.
The writer is much indebted to many
colleagues and other friends for assistance
in carrying out the present investigations,
which he began more than ten years ago.
Among these are the officials of the London
Zoological Society, Mr. Chas. H. Hicks in
particular; Professors James R. Slonaker and
Frank W. Weymouth of Stanford University;
Mr. C. W. Beebe, of the New York Zoloogical
Park; Mr. Cy de Vry of Lincoln Park, Chi-
cago, and the officers of the Golden Gate Park,
San Francisco, California; and Mr. Arthur
W. Head (the well-known artist) who has so
ably depicted and reproduced in this work
the avian fundi therein described. His thanks
are also due to Mr. C. H. Kennedy, now of
Cornell University, who has drawn so faith-
fully most of the black and white figures in
Chapter VII, illustrating the macroscopic
findings of preserved specimens. He is also
under obligations to Mr. Douglas Fyfe, who
made for him a collection of birds' heads in
the United States of Colombia; to Lieut.-Col.
J. W. Barrett of Melbourne, who performed
the same service in Australasia, and to a num-
ber of Calif ornians, among them Messrs. Van
Rossem, Wright M. Pierce, R. H. Beck,
Lieut. Casey Hayes (U. S. Army) and the
Managers of the Cawston Ostrich Farm and
Bentley Ostrich Farm, who furnished him
with abundant material from the Pacific
Coast. He also owes his thanks to Professor
J. Grinnell for the loan of material from the
Museum of Vertebrate Zoology of the Uni-
versity of California; to Dr. T. A. Woodruff

THE FUNDUS OCULI OF BIRDS

who assisted him in his earlier ophthalmo-
scopic studies of Birds, and to Professor Henry
B. Ward of the University of Illinois for
assistance in reading the proof sheets as they
were passing through the press.

The systematic classification employed for
the purposes of this work is that of Bowdler

Sharpe's Hand-List of Genera and Species
(London, 1909), except that in mentioning
North American Birds the specific names on
the Check List of the American Ornitho-
logical Union (1910) has been used.

Casey A. Wood.
Chicago, 1917.

Chapter II
SUMMARY OF CONCLUSIONS

1. The examination of the eyes of Birds
is a study of the most advanced and most
varied apparatus for the highest expression
of vision known to any vertebrate class.

2. The examination of the interior of the
avian eye through the pupil of animate species
(ophthalmoscopy) gives valuable information
regarding the function of sight in general and
of the eyesight of Birds in particular.

3. The fundus oculi, or background of the
eye, is plainly seen in its normal relations
when viewed during the life of the species,
and in many respects this form of exploration
is superior to methods carried out on prepared
or preserved eyeballs.

4. The parts and organs visible by the
ophthalmoscope in the eye of the Bird are in
particular (a) the concavity or general chorio-
retinal surface of the posterior half of the
eye; (b) the pecten; (c) the optic nerve en-
trance; (d) the areas of acute vision; (e) the
fundal bloodvessels; (J) opaque nerve fibres.

5. The appearances of these organs and
tissues furnish entirely different, colored fun-
dus pictures, and it is frequently possible to
recognize a species by viewing its fundus
oculi.

6. The fundus oculi of Birds exhibits a
great variety of areas of distinct vision, and
these correspond closely to the habits and
habitat of these animals — especially their
methods of obtaining food, of escape from
enemies, of migration, of reproduction, etc.

7. In spite of recent advances in that di-
rection, attempts to reproduce the colored
(ophthalmoscopic) appearances of the fundus
by photography have so far failed.

8. The macroscopic appearances of the
ocular fundus resulting from an examination
of preserved specimens have a value in this
research all their own; for certain forms of
examination it is inferior to ophthalmoscopy,
for others superior; but it gives no indication
of the color tones of the background so well
shown by the ophthalmoscope.

9. As in ophthalmoscopy, attempts to re-
produce the details of the eyeground of pre-
served specimens have so far given unsatis-
factory results.

10. The use of the microscope in examin-
ing the avian eye, and especially serial sec-
tions of the parts, is occasionally required
to settle anatomical questions that neither
ophthalmoscopy nor macroscopy can eluci-
date.

11. Domestication or prolonged captivity
brings about abnormal changes in the eye-

- ground of Birds, so that only healthy, wild
specimens should be utilized in this or a
similar research.

12. As the colored pictures seen in the
fundi of healthy wild birds are invariable in
species these appearances may well furnish
data for a classification of Aves ranking in
importance with other taxonomic indications.

13. Ophthalmoscopy throws light on the
origin of Birds, or at least on their relation
to that Sauropsidian ancestry which they
hold in common with Reptilia.

14. In future no report upon a particular
avian species can be held complete that
ignores the visual apparatus, and especially
the appearances of the fundus oculi as shown
by the ophthalmoscope.

[7]

Chapter III

COLLECTION, SELECTION AND PREPARATION OF MATERIAL

BIBLIOGRAPHY

Although the eyes of many hundreds of
species have been examined by the writer
ophthalmoscopically and otherwise his pur-
pose in this work is to describe as nearly as
may be the conditions found in the fundi of
such birds (especially of living birds) as are
most likely to be useful in a study of com-
parative ophthalmology. To this end he
has confined his attention to normal wild
species and has studiously avoided domesti-
cated, domestic or otherwise abnormal birds.
It is in these more or less tame species that
numerous variations from the normal eye-
ground are seen; consequently it is quite im-
possible to deduce from fundus examinations
of tame or diseased birds any physiological
conclusions worthy the name. This choice
of normal, wild birds has added somewhat
to the difficulties of the task. Domesticated
animals are the most accessible and the
easiest to examine; but any one who has
made a study of the matter will soon discover
that, as in Man, specific variations of the
fundus picture in domesticated species are so
numerous as to render it impracticable for
any one, even in a long lifetime, to make a
complete investigation of the ocular back-
ground in more than a few of these animals.
Even in an examination of the eyes of birds
in a public aviary the length of time the
individual has been held in captivity is of
importance from the ophthalmoscopic stand-
point; recently caught, healthy specimens are
always preferable to birds that have been
long confined and exposed to the unwonted
surroundings of cage life.

In addition to such wild birds as are acces-
sible in private collections or that are to be

found in every zoological garden or park,
the field naturalist may himself, or by proxy,
trap or shoot the specimens he needs. Many
birds can be procured through collectors em-
ployed by Museums and Colleges, either as
duplicates or in conjunction with the col-
lectors' other work. The writer, armed with
a proper license, has made several collecting
trips of this kind and has in this way been
able to examine the fundi of many disabled
or recently killed birds.

A self-luminous ophthalmoscope (see page
30) and a large opaque, black umbrella are
the most useful implements for field work.
A few minutes before and after the death
of the specimen one finds the pupil widely
dilated, so that the ocular interior can be
readily explored. Birds that are uninjured
or merely "winged" are placed in a box or
cage and carried to the laboratory or dark
room, there to be examined ophthalmo-
scopically at greater leisure. See Chapter VI.

(For macroscopic studies of the fundus in
prepared material the bird's head should be
placed in a preserving fluid — preferably
Perenyi's — a few minutes after death. In
collecting specimens the following rules should
be observed:

1. When possible, secure at least three
heads of each species. 2. Immediately after
death incise the skin about the neck well
below the head and carefully remove the skin
from the head by pulling it forward, wrong
side out, over the head, cutting the thin mem-
branes about the eyes (at the margin of the
orbit) without injury to the eyeballs. If the
eyes or their appendages are cut or injured
in any way the specimen is rendered useless.

[8]

COLLECTION, SELECTION AND PREPARATION OF MATERIAL

Diseased or injured eyes are also of no use in
this investigation. 3. After skinning, sever
the head from the body by decapitation close
to the base of the skull. 4. Label the head
by tying a string — to which a label is at-
tached — securely through the nostrils on
the beak. This label should bear, written
distinctly with a hard pencil, both the common
and zoological name of the bird, the date and
locality of collection, as well as the name and
address of the collector. Heads of the same
species should be numbered serially (1, 2, 3,
etc.). 5. The foregoing operations should
occupy as brief a time as possible. The head
should then be immersed in a quantity of
fresh Perenyi's fluid equal to twenty times
the volume of the head. Fruit jars are con-
venient containers for this purpose. For-
mula of Perenyi's Fluid: 10% nitric acid in
clean water (10 acid to 90 water), 4 parts;
95% (commercial grain) alcohol, 3 parts;
0.5% chromic acid in clean water (grm. 0.50
acid to 100 cc. water, 3 parts. After a few
minutes this mixture turns a violet color.
It may be kept in bulk indefinitely if well
corked. 6. Leave the heads in Perenyi's
fluid until the hardest bones of the skull be-
come soft and pliable when touched with a
scalpel. The time required will depend upon
the size of the head. The following periods
of immersion will usually be sufficient : Small
heads, as sparrow, robin, etc., 24 hours; me-
dium sized heads, as the crow, 36 hours; large
heads, as the owl, 48 hours ; extra large heads,
as the ostrich, 3 to 4 days. 7. After decal-
cification in Perenyi's fluid the heads should
be treated with the following percentages of
commercial grain alcohol. In each case use
approximately 20 volumes of the alcohol
solution to one volume of the head. The best
results are obtained by using fresh alcohol solu-
tion for each head. Leave the heads in each
of these alcohols for the same period they were
immersed in Perenyi's fluid. 70% alcohol is
made by mixing 70 volumes of 95% (commer-
cial grain) alcohol with 25 volumes of clean
water; 80% alcohol, made by mixing 80 vol-
umes of 95% alcohol with 15 volumes of clean
water; 95% (commercial grain) alcohol. 8.
After treatment with the last alcohol solution

the heads may be packed in a fruit jar suffi-
ciently large to hold them, covered with 95%
alcohol and carefully sealed to prevent leakage.

Should the eyeball lose its rotundity, or
"cave in" anywhere, the defect may be some-
times remedied by injecting 70% alcohol, by
means of a hypodermic syringe, into the
vitreous chamber.

Prepared in this way the bones of the skull
and the sclerotic plates are so softened that
sections of them can readily be made, while
the walls of the eyeball are so hardened that
they can be bisected at the equator with a sharp
razor and the anterior segment removed, with
the cornea, lens and vitreous. The parts
behind, in the posterior half of the globe,
constituting the fundus ocidi, eyeground or
background of the eye, remain in situ and can
be readily examined.

Although injection of the arteries of the
avian fundus is not as useful as in those eyes
in which there are retinal vessels, yet occa-
sionally the choroidal bloodvessels and (per-
haps) the pecten are affected by it and thus
rendered more visible. In that case prefer-
ably the gelatine-carmine mass of Ranvier is
injected by way of the carotid arteries.

In examining macroscopically the posterior
segment of the eyeball a magnifying lens of
10 cm. focus may sometimes be used but the
unaided eye is generally satisfactory.

On removing the hardened vitreous (by
means of a mounted needle) the grayish,
translucent retina should lie smoothly on the
choroid when the preparation is a success.
Retinal wrinkling occurs not infrequently in
some part of the eyeground, in which case it
may give rise to errors in determining the
presence or absence of some of the areas of
distinct vision, etc. A well preserved eyeball
furnishes satisfactory material for many years.

For microscopic sections a window is cut in
the globe in the plane of the desired sections,
the vitreous removed without injury to the
choroid and retina and the cavity filled (by
immersion) with celloidin. However, as the
minutiae of this form of investigation is out-
side the scope of this work the writer must
refer the reader to laboratory textbooks on
the subject.

THE FUNDUS OCULI OF BIRDS

BIBLIOGRAPHY

In addition to the well-known manuals on
ornithology, ophthalmology and biology the
writer has had most help in this investigation
from the following:

Abelsdorff, G., Uber das Verhalten des Pektens bei

der Akkommodation des Vogelauges. Archiv f.

Vergleichende Ophthalmologic, 1 Jahrgang, III Heft,

No. 3, pp. 290-292, 1910.
Abelsdorff-Wessely., Vergleichend physiologische

Untersuchung liber den Flussigkeits-Wechsel des

Auges der Wirbelthierreihe. lte, Theil, Vogel,

Archiv fiir Augenheilkunde, Vol. 64, pp. 65-124, 1909.
Audubon, J. J., Ornithological Bibliography, Vol. 2,

pp. 33-47, 1835.
Bayer, Jos., Bildliche Darstellung des gesunden und

kranken Auges unserer Hausthiere, Wien, 1892.
Beauregarde, M., Note sur l'etude ophtalmoscopique

du Peigne de l'oeil des Oiseaux, Compt. Rend, et

Mem. Soc. de Biologie, Paris 6 ser., T. 2, pp. 132-136,

1875.
Beddard, Frank E., The Structure and Classification

of Birds, London, 1898.
Beebe, C. William, Bird Portraits, Birds and Nature

Magazine, Vol. 1, No. 1, p. 12, May, 1907.
Beer, Theodor, Studien Uber die Akkommodation des

Vogelauges, Pfluger's Archiv, LIII, pp. 175-237,

1893.
Belogowy, J., Zur Entwickelung der Kopfnerven der

Vogel, Bull. Soc. Natural, Moscou, p. 177, 1908.
Bernd, Adolf Hugo, Die Entwicklung des Pecten im

Auge des Hilhnchens aus den Blattern der Augen-

blase. Inaugural-Dissertation, Bonn, 1905.
Bruecke, E., Uber den Musculus Cramptonianus und

uber den Spannmuskel der Choroidea, Mueller's

Archiv f. Anat. u. Phys., p. 370, 1846.
Bruhin, Th. A., Die Iris der Vogel insbesondere der

Raub, Sumpf und Schwimm Vogel der deutschen

Fauna, als unterschiedenes Merkmal der Arten, des

Alters und Geschlechts, Zool. Garten, p. 290, 1870.
Cameron, John, On the development of the layers of

the retina in the chick after the formation of the

optic cup, Proc. Royal Soc. of London, Vol. 70,

p. 84-86, 1902.
Canfield, William B., Vergleichende anatomische

Studien iiber den Accommodationsapparat des

Vogelauges, Arch. mikr. Anat., Vol. 28, p. 121-70,

1886.
Carpenter, F. W., The Ciliary Ganglion of Birds,

Folia Neuro-Biologica, Vol. 5, p. 738, 1911.
Chievitz, Uber das Vorkommen der Area centralis

retinae in den vier hoheren Wirbeltierklassen, Archiv

fiir Anat. und Physiol. Anat., pp. 311-334, 1891.
Cole, Leon J., Have all Eyes the Power of Forming

Images? American Academy of Arts and Sciences,

Vol. 42, No. 16, January, 1907.

Collin, R., Premiers etudes du developpement du
muscle sphincter de l'iris chez les oiseaux, Soc. Biol.
Paris, Vol. 55, p. 1055-56, 1903.

Collins, E. Treacher, The Anatomy and Pathology
of the Eye, Lancet, Feb. 17 and 24, 1900.

Coues, Elliott, Bird's-Eye Views, American Natural-
ist, Vol. 2, No. 10, p. 505, Dec, 1868.

Dennissenko, G., Uber den Bau und die Funktion
Kammes (Pecten) im Auge der Vogel, Arch. f.
mikrosk, Anat., Vol. 19, p. 733-41, 1881.

DrxoN, Geo. Sloan, Stereoscoping macroscopical
Eye specimens in glycerine jelly under glass,
Archives of Ophthalmology, Vol. 37, p. 40, 1908.

Dogiel, A. S., Die Retina der Vogel, Arch. mikr.
Anat, Vol. 44, p. 622^18, 1895.

Edinger, L., A. Wallenberg and G. M. Holmes,
Untersuchungen iiber die vergleichende Anatomie
des Gehirnes, 5. Untersuchungen iiber das Vorder-
hirn der Vogel, 1903.

Eigenmann, Cave (Blind) Vertebrates of America,
Carnegie Institution of Washington, 1909.

Franz, V., Der Facher im Auge der Vogel, Verh.
Dtsch. Zool. Ges., 1908

, Das Vogelauge, Zool. Jahrb., Abt. f. Anat., Vol.

28, pp. 73-282, 1909

, Bau des Eulenauges und Theorie des Teleskop-

auges, Biol. Centralbl., XXVH, No. 9 and 10, p. 271.
Leipzig, 1907.
-, Photographien mit ultra violettem Lichte.,

Archiv f. Vergleichende Ophthalmologic, I, Part III,

No. 3, pp. 283-289, 1910.
Fritsch, Gustav, (Berlin). Uber Bau und Bedeu-

tung des Area centralis des Menschen, Berlin, 1908.
Froriep, August, Die Entwickelung des Auges der

Wirbeltiere, p. 138.
Furbringer, M., Untersuch. zur Morphol. und

Systematik der Vogel, Parts I and II Amsterdam,

1888.
Gadow, Hans, Vogel. Sechster Band, IV Abteilung,

der H. G. Bronn'schen Klassen und Ordungen des

Tier-Reichs, Leipzig, 1912.
Gaskell, W. H., The Origin of Vertebrates, London,

1908.
Gegenbaur, Carl, Vergleichende Anatomie der Wir-

belthiere, Leipzig, 1898.
Greene, W. T., Parrots in Captivity, 3 Vols.
Heine, L., Physiologisch-Anatomische Untersuch-
ungen iiber die Accommodation des Vogelauges.

Arch, f. Ophthalm., Vol. 45, pt. 3, p. 469. 1898.
Herrick, C. J., Illustrations of the surface anatomy

of the brain of certain birds. Jour. Comp. Neur.

Psych., Vol. 3, 1893.
Hess, C, Vergleichende Physiologie des Gesichtssinnes,

1912.
Hoffmann, F. W., Zur vergleichenden Anatomie der

Lamina cribrosa nervi optici und einiger angrenzen-

den Verhaltnisse. Archiv fiir Ophthalmologic, XXIX,

2, p. 45-72, 1883.

COLLECTION, SELECTION AND PREPARATION OF MATERIAL

Ischreyt, C, Zur vergleichenden Morphologie des

Entenauges, Archiv f. Vergleichende Ophthalmologic,

III, No. 9, p. 39, 1912.
Jegebon, J., Uber den Einfluss des Sympathicus auf

die Vogelpupille, Arch. f. ges. Physiol., Vol. 41,

part 7-8, 1887.
Johnson, George Lindsay, Contributions to the

Comparative Anatomy of the Mammalian Eye,

Chiefly based on ophthalmoscopic examination.

Phil. Trans. Royal Society of London, 1901.
Kalt, M. E., Anatomie et Physiologie comparees,

Section of the Encyclopidie frangaise d'ophtalmologie,

p. 585, Vol. 2, 1905.
Kratjse, W., Uber die Retinazapfen der nachtlichen

Tiere, Archiv fiir mikroscopische Anatomie, XIX,

p. 309-314, 1881.
Langley, Z. N., and Anderson, H. K., The Action of

Nicotin on the Ciliary Ganglion and on the Endings

of the Third Cranial Nerve. Jour. Physiol., Vol. 13,

pp. 460-468, 1892.
Lenhossek, M., Das Ganglion Ciliare der Vogel, Arch.

f. Mikros. Anat. und Entwickl., Vol. 76, Part 4,

pp. 745-769, 1911.
Leplat, Georges, Contribution a l'etude de l'ac-

commodation chez les oiseaux. Annates d'oculis-

tique, p. 404, 1912.
Leuckart, Rudolph, Organologie des Auges; Ver-
gleichende Anatomie, Graefe-Saemisch Handbuch

der Gesamten Augenheilkunde, lte Edition, II, pp.

145-301, 1876.
Loewenthal, N, Beitrag zur Kenntnis der Harder'-

schen Druse bei den Saugetieren. Anatom. Anzeiger,

Vol. 7, pp. 546-556, 1892.
Meves, Wilhelm, Die Grossen und Farben der Augen

der Europaischen Vogel sowie der in der palaeartisch-

en Region vorkommenden Arten in systematischer

Ordung nach Carl J. Sundevall's Versuch einer

natlirlichen Aufstellung der Vogelklasse. 2nd

Edition, Jan., 1911.
Meyer, H., Uber einige pharmakologischen Reak-

tionen der Vogel und Reptilieniris. Archiv f.

experiment. Path, und Pharmakologie, Vol. 32,

1893.
MtJLLER, H., Ges. und hinterl. Schriften tiber das

Verhandensein zweier Foveae in der Netzhaut vieler

Vogelaugen, p. 142.
Nussbaum, M., Die pars ciliaris retinae des Vogelauges.

Graefe-Saemisch Handbuch der Ges. Augenllk. 2nd

Edition; and Archiv f. mik. Anat. und Entwicke-

lungesch., Vol. 57, pp. 347-350, 1901.
Parker, W. K., On the Morphology of Birds, Pro-
ceedings of the Royal Society of London, 1887.
Parreidt, R., BeitrSge zur Anatomie des Auges bei

Endyptes chrysocome und zur Entwickelung des

Pekten im Vogelauge, Inaugural Dissert., Leipzig,

p. 28, 1901.
Pflugk, A. von, tUber die Accommodation des Auges

der Taube, Dresden, 1912.

Putter, August, und Andere. Vergleichende

Physiologie, Jena, 1911.
, Organologie des Auges. Graefe-Saemisch Hand-
buch der Gesamten Augenheilkunde, ler Teil, 2ter

Band, 10ter Kapitel, 1908.
Ramon y Cajal, and Richard Greeff, Die Retina

der Wirbelthiere. Untersuchungen mit der Golgi-

Cajal'schen Chromsilbermethode und der Ehr-

lich'schen Methylenblaufarbung, 1894.
Schafer, G., Vergl. physiologische Untersuchungen

iiber die Sehscharfe. Pfliiger's Archiv, Vol. 119,

p. 571, 1907.
Sharpe, R. Bowdler, A Hand-List of the Genera and

Species of Birds. 5 Vols., Trustees of British

Museum, London, 1909.
Shufeldt, R. W., Osteology of Birds, Education

Department Bulletin, No. 447, University State of

New York, 1909.
Slonaker, J. R., A comparative study of the areas of

acute vision in vertebrates. Jour. Morphology,

Vol. 13, pp. 445-502, 1897.
Tornatola, Sulla membrana limitante interna della

retina nei vertebrati. Anat. Anzieger, Vol. 24,

pp. 536-538. [1903.]
Turner, C. H., Morphology of the avian brain, Jour.

Comp. Neur. and Psych., Vol. 1, pp. 39-92, 1891.
Virchow, H., Facher, Zapfen, Leiste, Polster, Gefasse

im Glaskorperraum von Wirbelthieren sowie damit

in Verbindung stehende Frage. Merkel u. Bonnet's

Ergeb. d. Anat. u. Entwickelungsgeschichte, pp.

720-849, Vol. 10, 1900.
Waelchli, G., Zur Topographie der gefarbten Kiigeln

der Vogelnetzhaut, Grafe's Arch, fiir Ophthalm.,

Vol. 29, pp. 205-24, 1883.
Wagner, R., Beitrage zur Anatomie der Vogel,

Abhandl. bayer. Akad. Wiss. Math.-phys., Vol. 2,

p. 270, 1837.
Wolff, H., [Photography of the Fundus.] Klin.

Monatsbl. f. Augenheilk., Oct.-Nov., p. 447, 1907.
Wood, Casey A., The Eyes and Eyesight of Birds, with

especial reference to the appearances of the fundus

oculi; Preliminary paper, Ophthalmology, April, 1907.
, Section on Comparative Ophthalmology; as well as

section on Birds, Eyes of, [The former the more im-
portant] American Encyclopedia of Ophthalmology,

pp. 2519-2763, Vol. 4, 1914; the second caption in

Vol. 2, p. 979 of the same treatise.
Wychgram, E., Uber das Ligamentum pectinatum im

Vogelauge. Archiv f. Vergleichende Ophthalmologic,

III, No. 9, I, p. 22, 1912.
Ziem, C, Geschichtliche Notiz ii. d. Facher im Auge

des Vogels. Zeitsch f. Psych, u. Phys. d. Sinnes-

organe, Vol. 6, p. 543.
Zietzschmann, Otto, Der Musculus dilatator pupil-

Iae des Vogels, Archiv fiir Vergleichende Ophthal-

mologie, Vol. 1, Part 1, pp. 9-19, 1909.
, Ellenberger's Handbuch der vergl. mikr. Anatomie

der Haustiere, p. 422, Sehorgan; 1906.

Chapter IV

A REVIEW OF THE ANATOMY AND PHYSIOLOGY OF THE

ORGANS AND TISSUES SEEN IN THE FUNDUS

OCULI OF THE BIRD

A comparison of the ocular structures in the
vertebrate sub-classes shows that the posterior
two-thirds of the eyeball contain practically
the same organs in all, with, of course, numer-
ous modifications of them to suit the visual
requirements of a particular species.

In Vertebrates generally the fundus organs
of especial interest are the retinal and choroidal
bloodvessels (in some instances projected into
the vitreous humor), the choroid, the retina
and the optic nerve entrance, the last named
otherwise known as the optic disc, porus
opticus, nerve-head or papilla.

Although the retinal layers are generally
transparent, and not visible during life, yet
this is not true of all species; e.g., occasionally
a certain number of translucent nerve-fibre
sheaths (neurilemmata) are prolonged into
the retina and variously distributed over the
background of the eye, and, by means of the
ophthalmoscope especially, are visible and
have been described under the name medul-
lated or "opaque" nerve fibres.

These organs and tissues will be considered
in their order.

Fig. 1

The Relations of the Fundus Organs of a Young
English Sparrow. A, area centralis; F, fovea; O, optic
nerve entrance; P, pecten. The pecten stands almost
vertical in this figure. (Wood and Slonaker.)

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The Temporal Monomacular Fundus of the Great
Horned Owl — Bubo virginianus. (After Slonaker.)
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ANATOMY OF THE FUNDUS ORGANS IN BIRDS

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THE FUNDUS OCULI OF BIRDS

The Avian Choroid
The choroid coat (choroidea) of Birds' eyes
is always very thin, even in large eyeballs,
but thicker than in the Mammal's eye. The
vascular, capillary meshes (choriocapillaris)
are of irregular size and rather narrow; in
Struthio the capillaries are 0.01-0.02 mm.
wide — broader than in other birds. The
spaces between the capillaries are, according

is seen at its widest about the time of hatch-
ing (when differentiation takes place most
actively) and becomes thinner and remains
permanent when the bird is several months
old.

A tapetum is absent in Birds, although the
Nubian Ostrich has a glass-like layer in the
choroid, of lamellated structure, capable of
reflecting light and producing color inter-

Fig. 7
Macroscopical, Postmortem Diagram of the Infulabimacular Fundus and Orbit of the Tern (Sterna hirundo).
N, optic nerve entrance; P, pecten; Ft, fovea and area temporalis; Fn, fovea and area nasalis; Ab, band-like

area. (After Slonaker.)

to Franz, completely free of cells and pigment.
The amount of pigment in the external layer
is subject to variation.

The thickness of this coat in Passer domesti-
cus is about 200 microns. The vessels of
the choriocapillaris measure from 10 to 20
microns in width; between them is a finely
punctate substance. This layer is 7 to 8
microns thick. Externally there is an endo-
thelial layer, then a net work of fine elastic
fibres without cells or pigment; finally, a
dense plexus of connecting cells.

The nerves run within the suprachoroidal
space and send only fine filaments into trabec-
ular that form a cavernous system throughout
the whole coat.

Slonaker found the choroid to be enlarged
and most vascular (see Fig. 1, just opposite
the fovea, especially in embryonal life and
in newly-hatched individuals. It is in the
former instance one of the indications of the
spot where the fovea will eventually form;
then it widens during the foveal formation,

ference effects. This arrangement, however,
is only a retino-choroidal variation, and not a
true tapetum.

The Retina of Birds

The acuteness of the eyesight in Birds is
largely due to the fineness and close arrange-
ment of the retinal elements. See Fig. 9.

Gustav Fritsch (Archiv f. Mikroskop. Anat-
omie, Vol. 78, p. 245, 1911) believes that true
rods and cones are found in Birds, just as
they are in Mammals, and they should be
designated as such. In the region of the
fovea centralis there is also a dwarfed, cone-
like form. The colored, retinal droplets of
Birds appear mostly in the rod elements,
although they are sometimes seen in conjunc-
tion with cones. Among the central cones is
also found, quite commonly, a body which is
colored brown by osmic acid.

According to Franz (Das Vogelauge, 1911)
the layers of the avian retina are more sharply
defined than in any other vertebrate; even

ANATOMY OF THE FUNDUS ORGANS IN BIRDS

more so than in Mammals. There are no
separate bipolar or optical ganglion cells in
Birds, while we find in Mammals isolated
amacrine cells, and, in reptiles, bipolar cells.
All birds possess rods as well as cones,
although in very different arrangements.
H. Miiller erroneously depicted the cones of
the Pigeon with long cylindrical extremities,

Figs. 8, 9 and 10

The Retina of Various Vertebrates

Fig. 8, Lizard; Fig. 9, Bird (Common Crow) ; Fig. 10, Mammal

(Dog). X510. (After P. Chiarini.)

when these really belong to the rods. The
cones have each a single oil droplet, whose
color varies. Cajal has differentiated (in
Birds and in Reptiles) "straight" and
"oblique" cones.

The nuclei of the cones usually lie inside
the membrana limitans externa of the retina.
Several "oblique" cones have an enlarge-
ment of the end inside the inner layer of
nuclei. The "twin" cones, whose nuclei are
not to be seen, lie near the membrana limitans;
the smaller nucleus of the pair is in a facet of
the larger. The rod nuclei are usually found
in the internal half of the nuclear layer. Their
small end branches in the outer reticular

layer, stretching out farther than the end of
the cone. The rod in nocturnal birds ends
in the external portion of the outer reticular
layer with a nodosity — a little ball at the
end without any branches.

Cajal differentiates three superimposed
plexuses in the external retinal layer; the first,
composed of the basal fibrils of the rods;
the second, the end-threads of the
straight cones; the third, fibrils
which emanate from the oblique
cones, that in every cell come in
contact with the dendrites of cer-
tain bipolars and longitudinal gan-
glion cells.

Just as in Reptiles, Schieffer-
decker found in the Chicken, Crow
and Goose, in the external reticular
nuclear layer, concentric supporting
cells without nuclei.

The inner nuclear layer of the re-
tina. One finds on the extreme
outer aspect horizontal ganglion
cells and (a) brush-like cells of Cajal,
with many projections and a long
horizontal cylinder which, like the
short projections, bends around the
outer reticularis and ends there
with an enlargement and branches;
(6) star-like cells with somewhat
longer dendrites and a short cylin-
der which first turns in and then
out. Between, and further in than
the cells, which Schiefferdecker calls
nucleated cells, are found two kinds
of bipolars; first, outer bipolars with highly
developed dendrites, and internal, small or
thin bipolars with weaker dendrites. The
thick bipolars seem to branch out in the fifth
layer of the internal reticularis; the thin
bipolars assume more the form of a layer in
the inner reticularis.

As in all animals, the nuclei of the sup-
porting fibres of Miiller in the avian retina
are situated in the internal nuclear layer.

In the inner portion of the internal nuclear
layer are found, as ganglion cells, the layer
of amacrine cells, which are divided, both in
Birds and Reptilia, into (1) nervous and
(2) proper amacrine cells.

THE FUNDUS OCULI OF BIRDS

The layer of ganglion cells. Cajal differ-
entiates the following types of ganglion
optical cells: (a) single-layered cells, spread-
ing out over the internal reticular layer,
partly multipolar, but mostly belonging to
the reticularis; (b) many -layered, multipolar
cells. The smallest are plentiful in the
Passeriformes; i.e., the Sparrow, Chaffinch,
Greenfinch, etc.

It should be noticed that Dogiel expressed
the opinion that those cells which in form,
size and character of branching of the pro-
toplasmal and cylindrical processes, belong
to a certain characteristic type, anastomose
with each other, or form a "colony."

The relatively thick, optic connective tissue
receives single, dissimilar, thick filaments,
which, originating centrifugally from the
optic nerve, intermingle with the internal
plexiform tissue and end, according to Cajal,
on the level of the amacrine cell-layer.

Specific differences in retinal elements. As
in almost all of the sub-classes of vertebrates,
there are differences in the retinae of Birds,
especially in the tissues of the rods and cones.

The numerical proportion of rods to cones
in different species is quite marked. Richest
in cones are the diurnal Birds of Prey. Cor-
responding to these in Night Owls are "rod-
retinae." M. Schultze thinks that while
Owls have many long rods, they have few
cones; Krause believes that the cones are
invisible on account of the number and length
of the rods, but that they are no less numer-
ous in the Owl than in the Falcon.

Geese have, according to Krause, many
long rods and stand in that respect midway
between Owls and diurnal Birds of Prey.
The Flamingo has the longest of all rod ex-
tremities. The Heron has many thick rods.

Krause seeks to weaken the force of the
statement of Schultze, that Nocturnal Birds
are distinguished by the preponderance of
cones and a diminished number of rods, by
pointing to the discovery of Heinemann that
in (the nocturnal) Nycticorax the rods are
scarce; that the Swallows, Hirundo rustica
and Chelidon urbica, in the relative increase
of their cones resemble the Owls, while
Athena noctua possesses even more cones than

rods. According to Hess, the number of
cones in the Owl's retina reaches 1 to 2^
millions.

However the teaching of Schultze has much
in its favor; insofar as that the hypothesis
supported by it, viz., that cones are really
color-percipient organs (the rods perceiving
light and form) finds proof in the fact that
rods alone are found only in the retinae of
deep-sea Fishes and Whales.

Regarding the possession of retinal oil
droplets, ellipsoids, paraboloids and hyper-
boloids, there are, according to Krause, many
differences in species. In Cardinalis virgin-
ianus and Fringilla spinus, he differentiated
two kinds of cones; in the Hen three outer
double cones. Fringilla spinus shows a blue
oil droplet in many of its double cones.

The layer of nerve filaments receives in the
Pigeon and a few other birds partly medul-
lated fibres. Franz finds in many birds that
the layer of nerve filaments in the vicinity
of the optic foramen corresponds to what in
Mammals are called "spider cells."

Pigment Movement in the Retina of Birds
Although this strange phenomenon probably
occurs in most vertebrates, and to a slight
extent in some invertebrates, yet it is in birds
that it is best studied. As Kalt remarks, the
retinal pigmented epithelium forms fringes
which, under the influence of light, descend
to the external limiting membrane. In the
dark they do not move past (at least in the
Pigeon) the middle of the rods and cones.

The purple of the retina is missing, accord-
ing to Kiihne, from the rods and cones of the
Hen and Pigeon. It exists in large quantities,
however, in the external segments of the rods
of the Screech Owl, while the cones are devoid
of it.

As Kiihne points out, the cones have vari-
able dimensions, and are single or double.
At the end of the internal segment they have
a single, oily, colored ball or droplet, which,
however, is not found in the interior of the
accessory cones. In a fresh retina the balls
show immediately with their various tints.

As far as the color of the retinal oil-droplet
of Birds in general is concerned, Schultze

ANATOMY OF THE FUNDUS ORGANS IN BIRDS

differentiates mainly (a) colorless, (6) yellow
to reddish-yellow and (c) red droplets.
Again, he finds a difference between Day
Birds and Owls in that the red are lacking
in the latter while the pale yellow and color-
less varieties are more plentiful.

According to Kalt, Waelchli distinguishes
four varieties of colored oil droplets in the
avian retina; red balls disseminated over the
whole membrane; orange, or yellow balls,
whose distribution is the same; greenish-
yellow ones seen at the periphery; and un-
colored ones spread in small quantities over
all. Osmic acid colors all these balls black.
The coloration is particularly intense in the
macular region.

The locality in which the colored droplets
are found varies with each tint. The green
balls are situated nearest the external sur-
face of the retina, the red come next, then
the yellow, and finally the colorless balls.

A chemical examination of the colored
globules in the cones of birds was made by
Kiihne. A hundred retinas of the Hen were
treated with alcohol and ether. The fatty
material thus dissolved (colored red) gave,
with soda, a soap from which was extracted
by petroleum ether a green coloring matter;
by sulphuric ether an orange material; by
turpentine a deep rose colorant; this last one
is, however, insoluble in sulphide of carbon.

Kiihne gave the names of chlorophane, xanth-
ophane and rhodophane to these pigments.

The Areas of the Retina in Birds. Avian
areae centrales are of greater variety — espe-
cially regions of distinct vision — and in
greater number than in other Vertebratse.

As described (see Chapter VII, page 59) and
depicted elsewhere (Figs. 110 to 115 inclu-
sive) the writer believes that there are at
least six forms of these arese in Birds.

According to Chievitz (1891) and Slonaker
(1897) there is at least one round macular
region with a fovea in practically all Birds.
This single area of monocular vision (see
Figs. 110 and 111) is in most Birds situated
somewhat centrally, slightly to the temporal
or the nasal side.

In many species, diurnal Birds of Prey for
example, besides a central fovea in the nasal

aspect of the retina, fovea nasalis, there is a
fovea temporalis, which with the fovea tempo-
ralis of the opposite eye may serve for binocu-
lar vision.

The area centralis retina?, macula lutea or
macular region, is found in all classes of
Vertebrates and its presence is the rule, espe-
cially in Reptiles and Birds.

The terms commonly applied to the various
parts of the macular region are as follows:
the whole area is designated the macula, or
area centralis or "yellow spot;" the more
sensitive, smaller area, generally disposed in
the geometrical center of the macula, is called
the fovea. Not infrequently there is seen a
still smaller point at the bottom of the foveal
depression; this is termed the foveola. This is
the terminology employed in human ophthal-
mology and there seems no good reason why it
should not be applied to all vertebrate eyes.

When the macula is placed on the nasal
aspect of the optic entrance it is called the
nasal macula or area nasalis; on the temporal
side, the temporal macula or area temporalis.
In the same way, one speaks of the area or
fovea nasalis and fovea temporalis.

The area centralis presents a thick portion
of the retina, where the arrangement of the
elements recalls that observed at the level
of the "yellow spot" of the human retina.
There is in this region an increase of gan-
glionic cells and of the receiving or percipient
elements — the cones and rods.

The depth of the fovea? may be regarded as a
measure of the sharpness of vision. Slonaker
classifies fovea? as deep, medium and shallow.
The round fovea is especially "deep" in
swift Fliers and Birds of Prey; "medium" to
"weak" in most other birds, except that it is
"shallow" in the domestic Pigeon, and prob-
ably lacking in the Hen.

Krause is probably right in believing that
domestication brings about the disappear-
ance of the fovea.

Both fovese in the bimacular fundi of diur-
nal Birds of Prey are structurally much alike,
in that they have in them only cones, and only
those with yellow droplets.

Besides this central area (with a fovea)
there is often, in Birds, a ribbon- or band-like

THE FUNDUS OCULI OF BIRDS

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ANATOMY OF THE FUNDUS ORGANS IN BIRDS

arrangement of retinal tissue that is generally
found in the horizontal meridian. It is mostly
seen in those birds that seek their food upon
the ground, e.g., Motocilla, Saxicola, Struthio,
Totanus, Tringa, Larus, Squatarola; also
in the Goose, Flamingo and other Aquatic
birds. See, for example, Figure 14.

Perhaps the retina manifests the greatest
foveal development in swift-flying birds. For
example, Cypselas, Hirundo and Sterna have
three fovea?.

Slonaker has also noticed an important
variation in the relative position of avian
fovea? and has offered an explanation borne
out by the results of this investigation; the
fovea nasalis is almost invariably found in
the same fundus area, but the locality of the
temporal fovea depends upon the position of
the eye in the head. As the eyes are turned
more and more forward the fovea temporalis
approaches the fovea nasalis. As binocular
vision becomes more frequent both fovea?
may become merged into one, generally
deeper, pit. There is also a corresponding
change to an asymmetrical form of the eye-
ball and to a peculiar position of the crystal-
line lens in birds with binocular vision.

In many such birds, the White-bellied
Swallow (see Fig. 5) and the various Terns
for example, the nasal fovea is deep and sharp,
while the temporal fovea is quite shallow and
the eyes are almost symmetrical; but in birds
with more marked binocular vision, Hawks,
for example, the temporal fovea has the
greater depth and the eye becomes more asym-
metrical. The climax is reached in Owls,
whose eyes are most irregular in form, who
have but one (deep) temporal macula and
who see only binocularly.

As with other organs in their body the com-
ponent parts of the visual apparatus of Birds
are arranged and adjusted mainly to enable
the Bird to obtain food and to escape his
hereditary enemies. In a minor degree, too,
we observe the influence of the necessity for
swift locomotion. Other (occasional) taxo-
nomic influences are apparent in certain special
visual requirements, such as nocturnal vision,
the use of the eyes under water, the employ-
ment of the eyes for vision both in air and

water, the visualization of minute objects
close at hand, etc. This statement is true
in full measure of the organs and tissues com-
prising the fundus oculi.

Stereoscopic, binocular, single vision in
Birds with double fovea? — and this is the
most acute, accurate and effective form of
eyesight that these or any other animals
know — is probably accomplished by the two
temporal fovea? acting in cerebral unison.
It is this form of sight, for example, that
enables the Osprey and other Hawks first to
locate from a distance and then to dart
unerringly upon their prey.

The deep and evidently more acutely func-
tionating nasal fovea is, in the writer's opin-
ion, employed for monocular vision only,
and there seems every reason to believe that
Birds with double fovea? have exceptionally
good eyesight with each eye separately; they
are, by this effective combination, enabled
not only to command a view of the highest
efficiency over the whole horizon, but also have
the power to concentrate it when needed upon
particular objects invisible or indistinctly
visible to other species not so provided.

It must, however, be acknowledged that
the neurology of Birds, involved in these
questions, is a sub-section of biology as yet
in its infancy; only when the histology,
pathology and experimental physiology of the
avian cerebral organs and their connections
have been worked out as they have been in
Man shall we know how the paths pursued
by "brain currents" involved in this switch-
ing from monocular single vision to binocular
sight run and are controlled. As these ques-
tions now stand the only certain thing that
can be said is that, with the possible exception
of the Owls, they must be totally unlike the
cerebral and spinal arrangements discovered
in Man and the higher Apes.

Of the physiology and psychology involved
in the ribbon- or band-like area we know still
less. In all probability it is a device to enable
swift-flying birds to take their prey on the
wing, and other species to find their food on the
ground while they themselves also stand on
terra fir ma; in other words, birds with banded
retina? possess eyes that are chiefly employed

THE FUNDUS OCULI OF BIRDS

in food-searching in such a fashion that they
are enabled to see one object very distinctly
and neighboring objects (in a restricted field
of vision) more distinctly than is permitted
by the comparatively insensitive retina of
the remaining fundal areas.

Infulapapillary angle. The relations, es-
pecially of fundal position, between the optic
nerve entrance, the pecten, and the areas of
distinct vision are, as we have already seen,
of some biological importance. Upon the
locality of the macular regions depend, in
great measure, the quality and precision of
the eyesight of each particular bird. That
one may facilitate references to the location
in the eyeground of the retinal band the writer
proposes to measure what he has termed the
infulapapillary angle (infula, a band, papilla,
the optic disc), made by the junction of the
major axis of the ovoid entrance of the optic
nerve prolonged until it meets the retinal
band on the nasal side of the point of contact.
In the case of the Hudsonian Curlew (see
Fig. 125) it is 50°.

The Optic Nerve of Birds

In all Vertebrates the optic nerve has the
form of a cord, sometimes very short, as in
Birds, and occasionally long, as in Man,
which extends from the optic foramen to the
posterior segment of the eyeball, where its
expansion forms the retina.

In Birds, whose ocular movements displace
the eyeball very little, the nerve takes the
form of a short, almost rectilinear cord; while
in animals with mobile eyes, such as the large
Mammifers, the nerve is long, round and
S-shaped, to follow the displacements of the
posterior hemisphere without pulling or drag-
ging. Its diameter greatly varies; it may
reach 8 mm., as in the Whale. The rule is
that it roughly corresponds in size and length
to the volume of the eye-ball.

As Kalt says, the pia mater forms the
neurilemma or sheath of the optic nerve.
The multiple partitions which it sends into
its substance, divide the nerve into bundles;
the dissepiments anastomose with each other.
This is the type well known among Mammals.
Birds exhibit one peculiarity; at the inner

aspect of the nerve the pial partitions pene-
trate perpendicularly into the substance of
the nerve and do not anastomose until they
reach about half way into the thickness of
the cord. Analogous perpendicular parti-
tions, but very short, exist sometimes on the
external side. The result is that the nerve
has a foliated appearance, especially marked
on the internal side.

The Pecten, Marsupium, Fan or Comb
of Birds

By means of the ophthalmoscope and direct
illumination there is seen, below and exter-
nally, in the fundus of every bird, a black
mass of variable form. When the free edge
of this organ is illuminated one notices a
longitudinal strip with undulating edges.
If one throws the light upon the base of this
object — the pecten or comb — the papilla
looks like a sparkling white area whose mar-
gins are edged with black, the center being
occupied by the irregular, black mass.

Fig. 13

Diagram Showing the Relations of the Optic Nerve
Entrance to the Pecten and the Basilar Artery and
Vein in the Sparrow. (Wood and Slonaker.) A,
artery to pecten, which sends a branch along each fold;
ch, choroid; on, optic nerve; pect, pecten; ret, retina;
scl, sclerotic; v, vein from pecten, which receives a
branch from each angle of the folds.

ANATOMY OF THE FUNDUS ORGANS IN BIRDS

The pectinate image seems to be displaced
by abrupt movements in the vitreous mass,
disturbances due probably to contractions of
the ocular muscles, external and internal.

As Kalt says, the pecten is a membranous
organ covered by a black pigment attached to
the optic nerve and projecting a variable
distance into the vitreous body. This organ,
studied and described for the first time by
Perrault, in 1876, received later the name
comb (peigne). The term "comb" is not
exact since there are no separate teeth; per-
haps "fan" better describes the appearance
of this organ. German authors still call it
the "fan" (Fiicher).

Except in the Ostrich, where it has the form
of a cone inserted into the optic nerve and
divided into two parts by a sort of white
partition, the pecten represents a triangular
or rectangular pigmented lamina, whose plane
is directed down and out.

Generally it does not extend into the
vitreous beyond the intercalary zone of the
sclerotic, and it is only exceptionally, as in
the Goose, the Swan, the Stork, etc., that it
reaches the crystalline lens. The comb is
made up of a lamina folded upon itself and
producing, in a transverse section, a markedly
zig-zag effect. The number of plications varies
from 5 to 30, averaging 16, as in birds of prey
and Gallinaceae. The writer and Slonaker
counted 18 folds in the English Sparrow.

Among the Owls, the length of the comb is
5 mm. at the base; its height, 4 mm. In the
Stork the base is 13 mm. long; it is 7 mm. high.

Kalt believes the pecten to be essentially a
vascular organ. It is composed of a network
of capillary vessels of unequal dimensions
spread out in two or three superimposed
planes, whose mesh may vary in form and
dimensions. In the Goose the vessels are
nearly all parallel; the anastomoses are rather
rare and the meshes acquire great length.
The thin connective tissue, which serves as a
support, contains free pigment. The entire
organ is enclosed in an envelope of endo-
thelium.

Kalt further thinks that the pectinate
blood-supply is derived from the external
branch of the internal carotid, which, imme-

diately after leaving the temporal, forms a
large plexus. The branches from this plexus
cross the sclerotic and re-unite in a single
trunk, which corresponds to the central ar-
tery of the retina in mammifers. This trunk
extends to the base of the comb, where it
gives off several ascending vessels, that pene-
trate the latter and form a large capillary
plexus. The venous blood is returned by a
large choroidal vein which perforates the
sclerotic a short distance towards the middle
of the comb. Note, also, that it makes at
the level of the ocular groove several variable
anastomoses with the plexus of posterior
ciliary arteries. See Figure 13.

According to Beauregarde the pecten is
allied to the choroid; it appears after the
fourth day in the embryo of the Hen.

The function of the pecten has from time
to time been variously interpreted. It has
been considered particularly as an erectile
organ capable of displacing the crystalline
lens and thus taking part in the accommo-
dation of the eye. Beauregarde, using the
ophthalmoscope, found displacements of the
organ and rapid vibrations synchronous with
the movements of the nictitating membrane.
But he noticed, above all, that the comb is
placed so as to intercept the rays coming
from the front and from above; that is to say,
those rays that reach the two eyes simulta-
neously. In catching them, the pecten is
supposed to suppress momentarily, in this
way, binocular vision, a condition which is
necessary for the more perfect use of monocu-
lar vision.

No doubt the pecten occasionally serves as
a screen to protect the retina against the raj's
of the sun. Observation of the attitude of
the Hen's head, when exposed to the sun, is
favorable to this supposition, as, also, the
slight development of this organ among
nocturnal birds.

Another hypothesis, which seems plausible,
attributes to the comb the role of an organ of
nutrition for the vitreous, and makes of it an
appendage of the ciliary body. It has also
been suggested that it is an organ of excre-
tion, charged with maintaining the intraocular
tension.

THE FUNDUS OCULI OF BIRDS

Franz does not believe that the fine struc-
ture of the bird's pecten has, as yet, been fully
described. The structural arrangement in
Struthio shows it to be different from other
birds, where it springs as a sort of wrinkled
leaf from the papilla and has an enlargement,
which he terms the "bridge," which runs
along the entire margin of the pecten. See
Figure 24 and Plate I. The folds are
welded together by this bridge, so that they
can only be smoothed out by cutting away
the latter.

The histological structure of the Bird's pecten
has been investigated by Mihalkowics, Denis-
senko, Bernd and others. Bernd claims that
the pecten is not primarily of mesodermal
origin and an appendix of the choroid, as was
formerly held (by Kessler, for instance), but
is really a derivative of the retina or of the
optic nerve; in short, an offshoot of the
central nervous system and, consequently,
of the ectoderm.

Franz maintains that the pecten is a sense
organ, assisting in the regulation of the intra-
ocular pressure and the act of accommoda-
tion. On the upper surface of the pecten,
that is on the "bridge," Franz found fila-
ments that end there in club-shaped bodies,
structurally between pigmented nuclei and
cell nuclei, and he believes we may look upon
the pecten primarily as a glia-structure, an
opinion also held by Blockmann and v.
Husen. Still, Franz will not say, nor does
Blockmann, that there is to be found in the
pecten any convincing evidence of the pres-
ence of true nerve filaments.

Franz and Hushke point out that the pecten
is all the more developed the more the bird
makes use of monocular, and less of binocular
vision; that the pecten of Song-birds is large
and rich in wave-like folds, while the much
faster flying Swallow, with better accom-
modation, has a more poorly developed pec-
ten. The Owls, also, with their small pecten,
have binocular fixation.

Both in Birds and Reptiles there is a close
connection between the pecten and the vitre-
ous; in other words between that organ and
the margins of the hyaloid canal, or slit, in
which it is, as it were, inserted.

Franz does not feel certain about the vas-
cular supply of the pecten of the Bird. He
believes, however, that the bloodvessel that
runs along the base of the pecten gives off
branches to the folds (as shown in Fig. 13)
and, to a less extent, to the pectinate bridge.
The main vessel is to be regarded as the
artery (afferent vessel) of the pecten.

We find glia-growths like those of the avian
pecten emanating from the papilla in many
Mammals and which present the same char-
acters as these organs in Reptiles. In the
eye of Amphibians and Fishes there are no
such glia-growths.

After many dissections and much considera-
tion of the finer anatomy of the organ Slonaker
and the writer do not regard the avian pecten
as anything more than a series of bloodvessels
with a deeply pigmented framework of glia
fibres and cells. So far we have been unable
to find in numerous serial sections of the
Sparrow's pecten (or in that of any other bird
so far examined by us) definite ciliated struc-
tures, sensory buds, or any other appearance
that would justify a belief other than that
this organ, deeply pigmented to absorb the
light rays, has any function apart from that
of a carrier of nutritive pabulum, chiefly to
the vitreous and anterior layers of the retina.
It may change its position, actual or relative,
during accommodation, but it has no other
connection with the accommodative act.
The covering of all its fan-like folds is con-
tinuous and identical with the hyaloid mem-
brane or membrana limitans of the retina.
We did not find in the Sparrow any anasto-
moses between the vessels of the pecten and
the other ocular structures. The branch of
the ophthalmic artery that enters the eye-
ball close to the optic nerve sheath (to pene-
trate the latter at the plane of the sclerotic
coat) is the only afferent vessel-supply of the
pecten that we were able to demonstrate,
either by gross dissection or in serial micro-
scopic sections of this region.

In the same way there appears to be only
one efferent vein which may, however, have
received other venules before its exit from the
globe, several millimeters distant. These two
latter observations are, however, based on an

ANATOMY OF THE FUNDUS ORGANS IN BIRDS

incomplete dissection of the parts and may
be modified later.

In this judgment, if we read him aright,
Treacher Collins, to some extent, concurs.
In his Erasmus Wilson Lectures on the Anat-
omy and Pathology of the Eye he remarks
that "in other animals than Mammals and
in the human fetal eye there are sources of
nutrient supply to the intraocular structures
in place of or in addition to the ciliary body."
He adds that the pigmented, plicated struc-
ture of the bird's pecten "closely resembles
the choroidal coat . . . having, however,
a rather finer capillary plexus. Birds, there-
fore, not only possess well-formed ciliary pro-
cesses but also a special vascular arrangement
in the vitreous chamber."

According to O. Zietzschmann, also, the pec-
ten is covered by a delicate membrane which
is continuous with the inner
limiting membrane of the retina.
The bloodvessels, according to
him, belong to the ciliary sys-
tem and are branches of those
supplied to the optic nerve.
Leber believes the pectinate ar-
tery to be the homologue of the
hyaloid artery.

Finally, it may be added that
there are no bloodvessels in the
Birds' retina and the vessels of
the pecten do not, consequently,
arise from a central artery of
the optic nerve as in Mammals
since that, too, is wanting.

This arrangement, inasmuch
as the opaque vessels do not,
as in most Mammals and other
Vertebratse, intercept the rays
of light impinging on the per-
cipient elements of the retina, makes for a
more distinct and measurably clearer-cut
image of the object visualized by the avian
brain.

Comparative ophthalmoscopy of reptilian
fundi. With the aid of Mr. Head's brush and
by courtesy of Dr. Lindsay Johnson the writer
is able to compare a few typical fundi of
Reptiles with those of their ancestral cousins
the Birds.

It requires only a glance at these pictures
to feel assured that the eyes of that nocturnal
reptile the Turkish Gecko (Plate LIX),
whatever else may be said on the subject,
are more decidedly avian or, rather, more
ornithosaurian than are those of the Horned
Toad (Plate LX), or Indian Cobra (Plate
LXI), whose fundi belong more distinctly to
other vertebrate types. These last-named
possess definite retinal vessels (that issue
from a circular optic papilla), and they have
no pecten or at least the mere suggestion of
one. Compare Plate LXI with Fig. 143;
and Plate LX with Fig. 144, which show
the resemblance between the Cobra fundus
and that of the Hedge-Hog, while the eye-
ground of the Horned Toad suggests that
of the Virginian Opossum. For further com-
parison a diagram of an ichthyan fundus

Fig. 14

Ophthalmoscopic View of the Fundus of the Fish Gadus merlangus.
(After Beauregarde.) The processus falciformis (black) runs the whole
length of the (white) optic nerve-head, at the peripherj' of which are seen
six branches of the hyaloid artery.

oculi (Fig. 14) — that of Gadus merlangus —
is shown.

If one may draw any conclusion from such
sparse material and from such an incidental
examination of the subject it is that whatever
of common origin the avian and reptilian
classes may have originally had the ornitho-
logical branch left the parent stem with a
subdivision of the Lacertilia and not with the
Ophidia.

Chapter V

OPHTHALMOSCOPY, OR THE EXAMINATION THROUGH THE

PUPILS OF ANIMATE SPECIMENS OF THE INTERIOR

OF THE VERTEBRATE EYE BY MEANS

OF THE OPHTHALMOSCOPE

Since this subject, although familiar to
ophthalmologists (oculists), is rarely under-
stood by naturalists in general, and espe-
cially not by ornithologists, a brief review of
ophthalmoscopy as practiced on the verte-
brate eye may not be out of place in a work
like this.

The ancients noticed that the eyes of some
animals are, under certain conditions, bril-
liant in twilight or semi-darkness. Although
he did not attempt to explain the phenome-
non, Pliny remarks that the eyes of animals
that see at night — cats, for example — are
radiant and shining, and that the eyes of
the she-goat and the wolf emit a light like
fire. This fact continued to be noted through
the succeeding centuries and was commented
on more or less by other observers. Jean
Mery of Paris, who in 1704 immersed a cat in
water, beheld in all its glory the fundus of
that animal's eye, including the optic nerve
entrance, the retinal blood vessels, and the
remarkable coloration of the retina and cho-
roid. Mery did not give a proper explana-
tion of this phenomenon, but five years later
de la Hire showed that the refractive power
of the cornea is neutralized by immersion of
the animal's eyes in water, so that all rays of
light reflected from a given point of the fundus
emerge from the pupil not as parallel but as
divergent rays; consequently the fundus im-
ages can be seen as if one were looking at them
in the depths of the eye through air.

The Fundus Oculi or Background of the
Internal Eye in Man. Glimpses of the human

ocular interior were obtained from time to
time but it was not until the year 1847, when
Babbage, an English mathematician, exhibited
to Wharton Jones, a well-known oculist of
his day, the model of an instrument by
means of which the interior of the eye could
be thoroughly examined. It consisted of
a small, plane, glass mirror from whose centre
a portion of the silvering had been removed.
This device was not made known to the world
until 1854, before which date the celebrated
physicist, Hermann von Helmholtz, published,
in 1851, a description of an ophthalmoscope
which enables the observer to see with ease
all the parts in the background of the eye.

The Ophthalmoscope. The original Helm-
holtz instrument consisted of four thin plates
of glass carefully polished, screwed together,
fastened at an angle of fifty-six degrees to a
brass disk, and forming the hypothenuse of
a right-angled triangular prism. The other
sides of this hollow prism were made of metal,
and all carefully blackened inside. The brass
disk had a hole in its centre and an arrange-
ment to place a concave lens over it; for
normal eyes Helmholtz used a No. 10 (4 d.)
glass. The light from a lamp falling on the
glass plates was in part reflected into the
observed eye, while the observer, looking
through the concave lens and the opening in
the brass disk, received the returning rays in
his own eye, and was able to see the fundus,
weakly illuminated, but still distinctly.

The instrument noio in use for examining
the interior of the eye more nearly resembles

[26

OPHTHALMOSCOPY OF THE VERTEBRATE EYE

the original ophthalmoscope of Babbage than
that of Helmholtz.

It consists essentially of a concave mirror
of about 25 cm. focus (mounted on a handle),
with a small (3 mm.) hole in the center and
so arranged that a series of concave and con-
vex lenses may be presented to the opening
for the purpose of neutralizing the refractive
error of the observer's and the observed eye,
thus giving a clear view of the fundus details.

There are numerous ophthalmoscopic mod-
els in the market today — improvements on
the early inventions — but the instruments
of Loring and Morton are, perhaps, the favor-
ite forms now in use. Illustrations of these
are given in the text. See Figs. 15 and 20.

As the purpose of an ophthalmoscopic ex-
amination is to see as much as possible of
the interior of the eye under observation it
is desirable to dilate the pupil; — in the case
of mammals this is accomplished by instilling
into the eye atropin, homatropin, euphthal-
min or some other mydriatic.

Befoe the invention of the self-luminous
or electric ophthalmoscope (Fig. 21) the source
of illumination of the ocular interior was a
gas jet or electric bulb — preferably an argand
lamp — stationed in a darkened room, and
placed on a level with the eye to the side of
the head.

In examinations of the human eye the
observer sits opposite the individual whose
ocular interior is to be explored, and placing
the mirror close to his own eye and about
40 or 50 cm. from the eye to be examined
reflects the light upon the latter, while he
looks at it through the small opening in the
ophthalmoscopic mirror. In very short-
sighted and very long-sighted eyes, but not
in normal ones, the vessels of the retina, the
entrance of the optic nerve, etc., can be more
or less distinctly seen.

The details of the retina, choroid, etc. (or
fundus), can be seen in two different ways.
In the indirect method, as applied to Man and
most other vertebrates, the observer, seated
as shown in the cut (Fig. 16), holds a strong
(16 d.) convex lens about 10 cm. from the
eye under examination, and between it and
his own, when a clear real image of part of

the fundus, inverted and magnified about four
diameters, appears in the red light of the
pupil.

In the direct method (Fig. 17) the observing
eye must be placed as close to the observed
as the intervention of the mirror will allow,
when a virtual image of a still smaller part of

Fig. 15
Loring Ophthalmoscope

the fundus is seen, but erect and magnified
about fourteen diameters.

Direct ophthalmoscopy, or the examination
by the upright or erect image, is illustrated
by means of Fig. 17. A side lamp (L) is
used, the rays from which are focused by the
perforated mirror of the ophthalmoscope (00)
and thrown into the observed eye through the
dilated pupil (P). The rays of this pencil
now cross about X and impinge on the retina
and choroid at OO and cover the ocular back-
ground from B to B. Thence a sufficient
number of efferent rays are reflected and re-
fracted back through the ocular media of
both the observing and observed eyes to the
percipient elements of the former, at L.

Another illustration (Fig. 16) shows indirect
ophthalmoscopy, or, as it is sometimes called,
the examination by the inverted image. A
divergent light pencil proceeds from the

THE FUNDUS OCULI OF BIRDS

Fig. 16

Indirect Ophthalmoscopy
Diagram showing the course of the light rays from the lamp, L, to the ophthalmoscopic mirror,
00, whence they are reflected to a focus, at F, where they diverge, to be once more focused by the
lens on to the retina at Zy, to be finally reflected to the eye of the observer at the opening in
the centre of the mirror, 00.

lamp, L, to the ophthalmoscope mirror, 00,
which focuses the rays at F. These sub-
sequently divergent rays are now made paral-
lel by the convex lens and are thus brought to a
focus on the retina-choroid by the dioptric
apparatus of the observed eye. Thence the
reflected and emergent rays follow the same
path and come to a focus, at X, in the eye of
the examiner who will see an inverted aerial
image of the observed fundus.

The electric self-illuminating ophthalmo-
scope differs from the types just pictured in
that it carries its own light source — a bat-

tery in the handle. It is peculiarly adapted
to the examination of the eyes of animals
other than Man. One is enabled through
this improvement not only to dispense with
the cumbersome side light but to make satis-
factory examinations of the fundus oculi in
only partially darkened surroundings — seri-
ous considerations in doing field work with
wild species. A picture of the latest model
of the self-luminous ophthalmoscope is shown
in Fig. 21.

The fact that a considerable portion of the
light thrown into the interior of the eye

Fig. 17

Direct Ophthalmoscopy
Diagram showing the course of the light rays from the lamp, L, to the mirror, 00,
whence they are reflected directly upon the observed retina at BooB. Thence they are
reflected through the opening in the mirror, 00, to the observer's eye at E.

OPHTHALMOSCOPY OF THE VERTEBRATE EYE

Fig. 18
Relative Position of Observer and Observed in Direct Ophthalmoscopy

Fig. 19
Relative Positions of Examiner and Examined in Indirect Ophthalmoscopy

THE FUNDUS OCULI OF BIRDS

through the pupil is reflected by the struc-
tures of the background into the eye of the
observer is the principle of the ophthalmos-
cope. Moreover, this reflection, or rather
refraction, of the incident rays, modified by

Fig. 20
Morton Ophthalmoscope

the character of the media through which
they pass furnish the wonderfully varied and
colored pictures observed in the ocular back-
grounds of all the vertebrates.

This brief account of the ophthalmoscope
and its method of employment is offered for
the benefit of those who have not used the
instrument, but no description of ophthal-
moscopy will much aid the zoologist in ac-
quiring a practical knowledge of its applica-
tion in the actual examination of animals'
eyes even in the favorable surrounding of the
darkened laboratory. Only a number of
months spent in the exploration of the eyes
of such domestic animals — including Man —
as are most readily accessible and easily ob-
served, followed by ophthalmoscopy of wild
species obtained in field work, will make an
expert of the student. While the writer will

not say that a practical knowledge of the oph-
thalmoscope is essential to the training of the
scientific zoologist yet it is an instrument that
furnishes precise and valuable information
which the naturalist cannot afford to ignore.

A. The Fundus Oculi or Background of the
Internal Eye in Alan.

On account of the extensive literature on
this subject and because the human fundus,
normal and abnormal, has been carefully and
thoroughly explored by many observers for
over half a century no study of comparative
ophthalmology is complete without at least
a short account of the ophthalmoscopic find-
ings in Man. In the writer's Encyclopedia of
Ophthalmology, Vol. VII, p. 5315 et seq.,
Moores Ball gives a good account of the
beautifully colored ophthalmoscopic picture
one sees in the depths of the human eye.
The parts of chief interest in the human fun-
dus are the optic disc, the blood-vessels, the
macula lutea, and the choroid, and they fur-
nish a satisfactory comparative study intro-
ductory to a consideration of avian fundi.

Fig. 21
Electric Self-luminous Ophthalmoscope (de Zeng).

The optic disc is situated about 3 mm. to
the nasal side of the posterior pole of the eye,
and is the point of entry of the optic nerve
into the retina. It measures from 1.4 to 1.7
mm. in diameter and is generally circular or
ellipsoidal in shape. Near its centre is a

OPHTHALMOSCOPY OF THE VERTEBRATE EYE

depression, the physiologic excavation, which
marks the divergence of nerve-fibres. The
excavation is funnel-shaped, the base being
anterior. A trace of the hyaloid artery of
fetal life is occasionally seen here as a thread
of connective tissue running from the papilla
into the vitreous. Surrounding the papilla
are two rings: an inner, due to exposure of

fibres, due to the fact that the medullary cover-
ing of the axis-cylinders exists in the fibre-layer
of the retina. In such a case the fundus shows
a patch of a brilliant white color extending out
from the disc. Generally the white area is in
contact with the disc. It rarely occurs that
the opaque fibres are found at a great distance
from the nerve-head or that they occupy a

Fig. 22

Diagram Showing the Relations of the Parts in the Human Fundus Oculi. a, sclera; b, choroid; c, retina;

I, macular region; 2, optic disc; 3, superior nasal artery; 4, inferior nasal artery; 5, inferior

temporal artery; 6, superior temporal artery; T, temporal side; N, nasal side.

the sclera, is whitish, and is called the scleral
ring; and an outer one, due to the showing of
choroidal pigment, is named the choroidal
ring. At the bottom of the excavation a
few dark spots are seen, from the gray stip-
pling of the lamina cribrosa. In color the
papilla is grayish-pink or reddish, and stands
out in marked contrast to the reddish-yellow
of the remaining parts of the fundus. The
color of the papilla varies with the age and
complexion of the individual, the color of the
surrounding parts of the fundus, and with
the illumination used. A common anomaly
is the presence or persistence of opaque nerve-

large area of the fundus. The physiologic cup
or depression may occupy a large part of the
nerve-head, but never extends to the scleral
ring. Under normal conditions many varia-
tions are seen in the size and depth of the cup
and in the arrangement of the blood-vessels.

The blood-vessels are the central artery and
vein of the retina. They run in the nerve-
fibre layer of the retina, and often present
variations of distribution. The middle of
the fovea centralis has no blood-vessels.

While it is often stated that the retinal
vessels can be seen on ophthalmoscopic ex-
amination, as a fact it is the column of blood

THE FUNDUS OCULI OF BIRDS

and not the vessel-wall, which is visible. In
the larger retinal vessels the blood-column in
the arteries is brighter than that in the veins.
In the smaller branches this difference is less
marked. The brighter color of the arteries
is due to the presence of a central streak of
light, which is less marked in the veins. The
cause of this light-streak is not definitely
known. The retinal artery, under normal
conditions, rarely pulsates, but venous pulsa-
tion occurs spontaneously in from 60 to 75
per cent of normal eyes.

Besides the blood-vessels enumerated
above, it is necessary to mention the cilio-
retinal vessels. These are commonly small,
solitary vessels which arise from the circle
of Haller, and emerge at the temporal border
of the disc. Such a vessel may come from the
central vessel in the substance of the nerve,
and may be of larger size. Generally it sup-
plies blood to a small area between the disc
and macula. Cilio-retinal vessels are present
in from 10 to 16 per cent of normal eyes.

The macula lutea ("yellow spot" of Soem-
mering) is situated about 3 mm. to the outer
side of the optic-nerve head, and slightly be-
low the horizontal meridian. It is a spot
darker than the surrounding retina and
apparently devoid of blood-vessels. It is the
area of greatest visual acuity. The centre
of the macula presents the foveal reflex, while
the periphery shows a whitish, glistening
ring, or halo, known as the macular reflex.
Differences in the appearance of the macula
in individuals are doubtless due to several
(mostly domestic) causes : to the difference in
methods of examination; to differences in the
age, complexion, race, and refraction, as well
as to variations in the distribution of pigment.

There are several forms of (ophthalmoscop-
ically visible) macular rings. Lindsay Johnson
states that the most common is a bright,
scintillating reflex resembling shot-silk, very
marked in dark eyes, scarcely visible in fair
ones, and best seen with feeble illumination.
This ring is supposed to be due partly to
reflection from Miiller's fibres, where they
expand into the internal limiting membrane,
and partly to the fibrous sheaths of the vessels
which lift up the retina over-lying them.

The foveal reflex is found in the centre of the
macula as a very small ring, or as a circular or
horseshoe-shaped spot of light, or as a "comet-
flare." It is due to reflection of the edge of
the fovea.

The choroid. While each ocular tunic con-
tributes something to the highly colored oph-
thalmoscopic picture, the chief part must be
credited to the choroid. Light reflected from
the mirror of the ophthalmoscope passes
through the transparent part of the retina
to the pigment epithelium, and is partly
absorbed, partly reflected. Although the
pigment layer belongs embryologically to the
retina, it generally adheres to the retinal
surface of the choroid, and is accredited oph-
thalmoscopically to the latter tunic. The
brightness of the fundus picture depends on
the amount of pigment. The greater the
pigment, the greater the absorption of light
and the darker the fundus picture. In the
negro and the native of India the fundus is
of a brownish, brown-red, or slate color, while
in the Anglo-Saxon, and particularly in
blondes, it is of a bright-red color. If the
pigment layer is very thin, the choroidal ves-
sels are correspondingly exposed and are seen
as a network of large, flat vessels, without a
light-streak, between which are spaces of light
or dark color. They are seen best in albinos.
It is generally impossible to differentiate
between the choroidal arteries and veins,
although at the equatorial region the latter
converge to form the venae vorticosse. In
brunettes the vessels appear as " light streams
separated by dark islands," because the spaces
are more deeply colored than the vessels.

The sclera, which may be spoken of as the
panel on which the fundus picture is painted,
is commonly invisible, being covered by the
nearly opaque choroid. Yet it is probable
that in all eyes some light passes through the
choroid, and thus the sclera has some in-
fluence on the ophthalmoscopic picture, serv-
ing to make it lighter. In albinos the sclera
appears as a white surface between the cho-
roidal vessels. It is best seen where the
choroid is absent, as in coloboma, or patho-
logically as a result of destruction of the
retina and choroid.

Chapter VI
OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

The method employed by the writer in ex-
amining the background of the eye in living
Birds does not much differ from that of the
physician in his examination of human eyes
as described in the previous chapter.

For a proper exploration of the vertebrate
fundus it is, as previously stated, highly de-
sirable that the pupil be widely dilated.
This is accomplished in Man and other Mam-
mals by such mydriatics as atropin, hom-
atropin, euphthalmin, etc., which bring about
an enlarged pupil mainly by inhibiting the
action of the non-striated sphincter muscle
fibres of the iris. In Birds, however, these
agents have little direct effect on the striated,
voluntary, sphincter musculature of the iris;
hence they are of little value in an ophthal-
moscopic examination of most Birds. One is
obliged, therefore, to resort to such agents as
galvanism, nicotine, strophanthin, curare,
stipticin, etc., and to such drugs (eserin,
atropia) as render the bird unconscious with-
out actually killing it.

In collecting the heads of birds for niacro-
scopical and histological studies the writer
found that satisfactory ophthalmoscopic
views of the fundi can be had a few minutes
before and after the death of the specimen,
during which period the pupil not only dilates
ad maximum but the bird does not use his
third eyelid. Many of the appended reports
were gathered in this way.

Owing to the peculiar arrangement of their
lacrimal apparatus (see the writer's work on
this subject) fluids instilled into the eye (con-
junctival sac) of Birds run immediately into
the throat and gullet, there to be absorbed
and to produce precisely the same systemic
effects as if they were poured directly down

the throat of the animal. Great care should
be used, therefore, in using eye drops for their
expected effect upon the visual apparatus;
if poisonous for the bird they may cause his
death in short order, and rare and valuable
specimens may be sacrificed to the ignorance
of the observer. The writer has not the least
doubt but that some of the so-called mydri-
atics or pupil-dilating drugs recommended for
an examination of the ocular interior of the
Bird act as systemic intoxicants and not
specifically upon the iris muscles, as is the
case with the mammalian eye.

As an example of this action of the so-
called mydriatics on the eyes of birds the
writer once fell into the same error as other
still earlier observers in attempting to dilate
by atropia the pupils of a Yellow Parakeet
{Melopsittacus undulatus). This bird was an
adult individual, sex unknown, in captivity
for six months. In dull light the pupils
were 2.5 mm. wide, contracting irregularly
to 1.5 mm. A single drop of a 1% solution
of atropia sulphate put into the eyes appar-
ently dilated the pupils ad max (3 mm.) in
12 hours, but as the bird was taken ill a few
hours following the instillation (stupor, ver-
tigo, quick, weak heart and final unconscious-
ness) and died 30 hours after the use of the
drops, it is quite likely that its death was due
to the poison that ran into its throat from the
conjunctival sac. The writer had a similar
experience with a number of other birds.

The following notes were made of experi-
mentation intended to determine the best
mydriatic for the Bird's eye, especially for
field work.

Laboratory Notes of Experiments on the
Pupils of Passer domesticus. One drop of

[33

THE FUNDUS OCULI OF BIRDS

a 1% mixture of curare put into left eye of
three adult English Sparrows, two <?, one 9,
at 11 a.m. Thursday, March 28, 1912.
Result negative at twelve o'clock.

April 1, 1912. Put one drop of }/2% nico-
tin into the left eye of two Sparrows, adults,
one 9, one <?, at 9:35 A. M. Pupils in each
case — half light — were 2 mm. in diameter
before the instillation. 10:15 A. M., no effect
as to dilation or reflex to light in 0% so then
put in one drop of 1% nicotin. Bird became
slightly "groggy" in 4 minutes. 10:20 A. M.
9, left pupil barely dilated more than right,
instilled 1 drop 1% solution nicotin: no gen-
eral effect in 5 min. 10:25, ditto &. 11:30,
very slight, if any difference in pupils. 2:25
p. m., same day, put a drop of 2% into left
eye of same 9 and d" sparrows. They both
became quite "groggy" in one minute but
recovered in five minutes so as to sit up and
fly easily about the cage. At 2 :40 p. m. no
change in pupil. 3:10 p. M., both birds quite
lively and both left pupils dilated to 3 mm.
At 4:30 tf's pupil dilated; 9 normal. Both
birds normal.

April If., 1912. Put one drop of 2% nicotin
into left eye of 9 at 10:40 a. m. Bird intoxi-
cated in 2 min. but revived in 5 min. Second
drop at 10:50: bird very "groggy" in 2 min.;
lay on its back in 3 min. breathing with
difficulty, dead in 4 min. ; widely dilated pupil
left; semi-dilated right.

March 30, 1912, 3 :30 p. M. Put one drop of
1% nicotin into the left eye of three adult 9 .
All became more or less "wobbly" in two
minutes, recovering almost entirely in 15
minutes. At 4 p. M. the pupils, left, were all
three dilated ad max., although when exposed
to the diffuse light of a north room they con-
tracted; almost to normal in a very bright
light. At 4 :30 p. m. the pupils were all nor-
mal except one, left, pupil which was slightly
and continuously dilated, and not much
affected by strong light. Put one drop of a
two per cent solution of nicotin into left eye
of two adult 9 at 12 o'clock. One died in
15 minutes, under complete collapse. The
other became very stupid and laid on her
stomach for % hour, after which she revived
but was not as lively as before. At 2 p. m.

the left pupil of living Sparrow was dilated
ad max, and but slightly affected by light.
Right pupil unaffected at 4 p.m.; both pupils
normal at 4 p. M.

March 26, 1912. Examined pupils in one
c? and two 9 1H to 2^ mm. in diameter.
They contract promptly in light to 1 mm.
Nicotin, both 1% and 2%, seems to "daze"
the birds. One drop of each solution, put
into the right eye caused paresis of lower lid
but not of nictating membrane; dilation of
pupil in 20 min. to 4 to 5 mm., which re-
mained in this condition for at least 13^2 hours.
Left eye as before. In 2j^ hours pupils
normal again. Bright light focused on dila-
ted pupil caused a contraction to 3 mm. which
instantly recovered to 5 mm. on medium
illumination. After 1^ hours 2% nicotin
dilated right eye of 9 to 6 mm. and it was
then only slightly affected by bright light.
One drop of a 2% pilocarpin hydrochloride
put into left eye of 3 adult English Sparrows,
two 9 and one d", at 11:25 A. M., March 28,
1912. Negative results at 12:00.

In other words, one per cent solution of nic-
otin brings about a dilation of the avian pupil
that persists for several hours, and is prob-
ably the best agent one can use for the
purpose.

Experience has proved that the self-lumin-
ous, electric ophthalmoscope having a small
eyehole in a "split" mirror is the best instru-
ment for exploring the avian fundus. Such
an instrument is described in Chapter V, and
there depicted as Fig. 21.

After a careful inspection of the anterior
parts of the eye, both without and with a
lens (to make sure that there is in the ob-
served eye no obstruction to an examination)
the observer should seat himself on a chair
in a dark room. Then, holding the instru-
ment against his own eyebrow with one hand
and a +20D. glass with the other hand, focus
the light from the ophthalmoscope, held at a
distance of about 40 cm., or 18 inches, from the
bird's eye, through the dilated pupil and upon
the fundus of the bird, firmly held by an
assistant seated opposite.

In field work both the observer and his
assistant may kneel on the earth under a

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

large, black umbrella, or make the examina-
tion in a darkened tent; in public or private
aviaries the examination can often be made
after sundown.

A four dioptre convex lens must be placed
in front of the eyehole of the mirror. This

species that present invariable ophthalmo-
scopic pictures. It will be found that after
two or three generations of inbreeding, con-
finement and domestication, changes occur
in the ocular apparatus coincident with varia-
tions in other parts of the organism.

Fig. 23

Method of Examining the Bird's Eye with the Self-luminous
Electric Ophthalmoscope.

"indirect" method (see, also, page 29) gives a
comparatively small, inverted image of the
ocular fundus. It corresponds to the low
power lens which one uses in the preliminary
examination of a microscopical section.

The examination by the erect image will, on
the whole, be found the most satisfactory
method, although, as in viewing the human
fundus, it is advisable to use the indirect plan
at the outset. The self-luminous ophthal-
moscope is quite satisfactory for both these
purposes.

In making an examination of the avian
fundus it must be remembered that it is wild

The facility (or otherwise) with which the
ophthalmoscope can be used depends, in a
large measure, upon the conduct of the bird
under examination. For instance, it is im-
portant that the macular region be carefully
explored and it can generally be seen, but
throwing the light on this very sensitive area
often makes the animal restless and the
greatest gentleness should be observed to
keep it quiet if a complete examination is to
be made. Most specimens, not excepting
the Eagles, Hawks, Vultures and other large
birds can be hypnotized and so quieted for the
period of an ophthalmoscopic examination.

THE FUNDUS OCULI OF BIRDS

To this end the assistant must, at first, quietly
but firmly hold the mandibles with one
(gloved) hand, the other pressing claws and
wings against his chest. In a few minutes
the bird ceases to struggle; the assistant's
grasp of the bird is then slowly relaxed; the
bird relaxes its muscles, no longer resists the
attempt to examine it and the head can
usually be turned in any desired direction
to suit the observer. See Fig. 23.

There is sometimes difficulty in seeing the
fundus of the bird because of frequent wink-
ing of the bird's nictitating membrane (rarely
through shutting of the true lids) and because
of occasional contractions of the pupil (unless
it is artificially dilated) but these difficulties
are, with time and patience, surely overcome
— and almost always without damage to the
bird, the observer or his assistant. Some
birds, Cormorants, for instance, resist at-
tempts to quiet them and become wild and
restless when the light from the ophthal-
moscope falls on the macular region; others,
like the Raven, remain quiet for irregular
periods during the examination but intel-
ligently await an opportunity to use bill and
claw on the captor.

As an extended study of the eyes of living
birds is not without its dangers, both the
student and his assistant should wear leather
gloves during the ophthalmoscopic examina-
tion and should especially be on guard against
facial bites, stabs and scratches — from the
mandibles and talons of Raptores and Par-
rots in particular. In addition to these acci-
dents, one of the writer's assistants was severe-
ly bitten by a European Raven, another was
badly kicked by an Ostrich, while the writer
himself barely escaped the loss of an eye from
a stab on the margin of the orbit inflicted
by the pointed beak of a Little White Heron.

Reference is elsewhere made to the possi-
bility of quieting or even of hypnotizing birds
for the purpose of making an ophthalmoscopic
examination. In some cases flashing the
light of the ophthalmoscope into the animal's
eyes produces a quieting effect.

The writer has had many such experiences
but he here relates only one. Assisted by
Head-Keeper Pitts of Bentley's California

Ostrich Farm and several San Diego col-
leagues he examined, in 1912, a young, adult
ostrich, six feet high, healthy and very vigor-
ous. The bird resisted capture and was thrown
only after a struggle. A keeper sat on his
prostrate body; another held his head and
neck. After the light of a self-luminous
skiascope had played over his dilated pupils
in a darkened room for about five minutes
he acted as if he were in a trance ; he remained
in the prone position without being held and
a complete examination of his pupil reflexes,
static refraction, fundus appearances, etc., was
made without difficulty. Finally, after about
20 minutes or half an hour (when this inquiry
was completed) the bird refused to move or
rise — and had to be pushed to his feet — after
which he became his lively self again.

The small pupils of Wrens, Nuthatches, the
smaller Warblers, Hummingbirds, etc., even
when fully dilated, make it extremely difficult
to view the fundus during the life of the bird
and tax the perseverance of the observer to
the utmost. It is, perhaps, well not to at-
tempt such tasks until the ophthalmoscopist
has had a year or two of experience. Annoy-
ing, also, are the fugitive reflections and
"shot-silk" colors that play over the retinal
areas in some birds, but even these fail to
obscure the fundus picture after some months
of practice.

The task of picturing the avian background
for the purpose of conveying an intelligent idea
of its appearance is a serious one; indeed, with
all the work done upon the eyes of Birds, this
method has been almost entirely neglected.
The ophthalmologist may be a good observer
but a poor artist; conversely, an expert in the
use of brush and pencil may not be sufficiently
conversant with normal and pathological,
human and comparative ophthalmoscopy and
ophthalmology to enable him to make an in-
telligent use of his artistic talents. These
difficulties have been, in this research, largely
met by an arrangement with Mr. Arthur
Head, F. Z. S., the well-known London artist,
who for some 20 years past has been painting
both human and animal fundi for confreres
here and abroad. This artist and the writer
have together examined and discussed in the

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

Fig. 24.
Nubian Ostrich (Struthio camelus).

Fig. 27.
Kiwi or Apteryx (Apteryx mantelli) .

Fig. 25.
American Ostrich (Rhea americana).

Fig. 28.
Martineta Tinamou (Calodromas elegans).

Fig. 26.
Westerman's Cassowary (Casuarius occipitalis).

Fig. 29.
Brazilian Seriema (Cariama cristata).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

THE FUNDUS OCULI OF BIRDS

Gardens of the London Zoological society the
ophthalmoscopic appearances of several hun-
dred avian and other eyes. The details of
these fundus views, as revealed by the oph-
thalmoscope in many species, are described
and depicted in Chapter X and elsewhere.

A. The Avian Eyeground in General.

The average eyeground or fundus oculi of
most Day Birds resembles, as much as any-
thing, the texture of the so-called "scotch
mixtures" in smooth finished cloth — usually
light brown, gray, gray-blue, blue mixed with
striate rays, or fine concentric marking of
lighter gray or white. Scattered over this
background are numerous yellowish, yellow-
white, brown or gray points of pigment.
Although this matter has not yet been satis-
factorily determined yet these punctate de-
posits are, in part at least, the colored oil
droplets described in Chapter IV.

Nocturnal Birds have, almost invariably,
yellow-red, orange, orange-red or reddish
brown fundi, with the choroidal vessels plainly
visible through the semitransparent retina.
Some of the Owls present almost a scarlet
vermilion eyeground, and this intensity of
colors appears to be peculiar to Strigiformes.
For this reason alone might say with confi-
dence that the New Zealand Owl Parrot
(Stringops habroptilus) belongs to this order
and not to Psittaciformes or to Cuculiformes
in one of which he is commonly placed.

Ophthalmoscopy of the areas of distinct
vision in Birds supplements the macroscopic
and microscopic examination. In many in-
stances it affords a better idea of the relations
of these arese than does any other means of
observation; at least this is true of most avian
fundi explored by the writer. As a rule the
deep, single fovea and its surrounding macular
region are, other conditions being favorable,
readily observed by means of the mirror, and
their locality, comparative size, component
parts, coloration, etc., easily depicted. Con-
trariwise, a shallow or organically ill-defined
"yellow spot" is not so readily made out.
Band-like areas are also better defined by the
aid of a magnifying glass and in prepared
half-eyes, although in the fundus of the
Secretary Bird (Plate XXXI), of the White-

bellied Sea Eagle (Plate XXXIV) and of a
number of other bimacular species the ribbon
of tissue is well shown by the mirror.

With, perhaps, this exception the macro-
scopic description of the arese centrales given
not only in the lists of Chievitz and Slonaker
but in Chapter VII corresponds in a remark-
able fashion with the ophthalmoscopic find-
ings described and depicted in this work.
Nothing has been discovered in this study of
the avian fundus by the aid of the mirror that
is likely to add to or subtract from the classi-
fication of the types of central vision sug-
gested by the writer in the same Chapter.

The Pecten and Optic Disc

Viewed ophthalmoscopically the avian mar-
supium or pecten exhibits three fairly definite
varieties which may be classified as follows:

I. Those pectens whose mass uniformly
springs from and equally covers the optic disc.
Such pectinate bodies do not extend into the
vitreous cavity farther than the length (often
less) of their widest segment, and they are
sessile on the face of the papilla. Examples of
this form of pecten are seen in Nycticorax
nycticorax (Fig. 45), Haliaetus leucocephalus
(Fig. 56), Caprimulgus europeus (Fig. 65),
Strixflammea (Fig. 59), Serpentarius (Fig. 52),
Struthio camelus (Fig. 24), Cancroma cochle-
aria (Fig. 46), Casuarius occipitalis (Fig. 26),
Spheniscus demersus (Fig. 37), Tinnunculus
alaudarius (Fig. 55), Calodromas elegans (Fig.
28) and Syrnium aluco (Fig. 58). This method
of arranging the pectinate tissues makes pro-
vision for a blood reservoir large enough to
supply nutritional needs but so placed that it
does not materially obstruct visual or light
rays. Such a disposition and configuration
of the fundal organs meet the needs of many
species, among them Eagles and Owls, who
require (and have) very acute vision.

II. Some pectens, while they originate from
the whole surface of the optic disc, immediately
slope away from the visual axis, approach the
bulbar wall and terminate without projecting
far into the vitreous. In this type there is
generally a disc-length or more between the
free terminal of the pecten and the posterior
surface of the crystalline lens.

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

Fig. 30.
Harlequin Quail (Coturnix histrionica) .

Fig. 33.
Common Wood Pigeon (Columba pcdumbus).

Fig. 31.
Brush Turkey (Catheturus lathami).

Fig. 34.
Victoria Crowned Pigeon (Goura victoria).

Fig. 32.
YarrelTs Curassow (Crax globosa).

Fig. 35.
Wonga Wonga Dove (Leucosarcia pieata).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

THE FUNDUS OCULI OF BIRDS

Fig. 36.
Ipecaha Rail (Ar amides ipecaha).

Fig. 39.
Herring Gull (Larus argentatus).

Fig. 37.
Black-footed Penguin (Spheniscus demersus).

Fig. 40.
Great Black-backed Gull (Larus marinus).

Fig. 38.
Puffin (Fratercula arctica).

Fig. 41.
Stone Plover (Oedicnemus scolopax).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

Fig. 42.
Little Bustard {Tetrax tetrax).

Fig. 45.
Night Heron (Nycticorax nycticorax).

Fig. 43.
Kagu (Rhinochettis jubatus).

Fig. 46.
Boat-billed Night-Heron (Cancroma cochlearia).

Fig. 44.
European Bittern {Botaurus stellaris).

Fig. 47.
American Jabiru (Mycteria americana).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

THE FUNDUS OCULI OF BIRDS

Fig. 48.
Blue Snow Goose (Chen cwrvlescens) .

Fig. 51.
Cormorant (Phalacrocorax carbo).

Fig. 49.

Red-billed Tree Duck (Dendrocygna autumnalis
discolor).

Fig. 52.
Secretary Bird (Serpentarius cristatus).

Fig. 50.
Gannet (Sula bassana).

Fig. 53.
Lammergeier (Gypaetus barbatus).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

Fig. 54.
White-bellied Sea Eagle (Haliaetus leucog aster) .

Fig. 57.
Burrowing Owl (Speotyto cunicularia) .

Fig. 55.
Common Kestrel (Tinnuneulus alaudarius).

Fig. 58.
Tawny Owl (Syrnium alvco).

Fig. 56.
American Bald Eagle (Halia'itTis leucocephalus) .

Fig. 59.
British Screech-Owl (Strixflammea).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

THE FUNDUS OCULI OF BIRDS

One finds examples of this form in Columba
palumbus (Fig. 33), Cuculus canorus (Fig. 66),
Catheturus lathami (Fig. 31), Larus argentatus
(Fig. 39), L. marinus (Fig. 40), Rhinochetus
jubatus (Fig. 43), Goura victoria (Fig. 34),
Chen cerulescens (Fig. 48), Mycteria americana
(Fig. 47), Speotyto cunicularia (Fig. 57),
Stringops habroptilus (Fig. 62), Chrysotis
amazona (Fig. 60), Rhea americana (Fig. 25),
Sula bassana (Fig. 50), Haliaetus leucogaster
(Fig. 54), Cacatua galerita (Fig. 61), Den-
droma autumnalis discolor (Fig. 49), Crax
globosa (Fig. 32), Fratercula arctica (Fig. 38),
Dacelo gigas (Fig. 63), and Botaurus stellaris
(Fig. 44).

III. This class includes those pectens (usu-
ally of slender proportions) that arise from the
whole surface of the optic papilla and, then,
either curve towards and folloio the concave wall
of the eyeball or they proceed in a straighter
line until they touch (or nearly reach) the poste-
rior surface of the lens, generally near its
equator. In most instances there is less than
a disc length between the pecten terminal and
the lens capsule. To this class belong the
pectens of Hirundo rustica (Fig. 71), Leu-
cosarcia picata (Fig. 35), Cyanospiza versicolor
(Fig. 73), Mimus polyglottos (Fig. 72), Spago-
lobus adratus (Fig. 64), Xanthura cyanocitta
(Fig. 75), Aramides ipecaha (Fig. 36), Apteryx
mantelli (Fig. 27) and Coturnix histrionica
(Fig. 30).

These are many species whose pectens
occupy a position intermediate between
Class II and Class III, and which are conse-
quently, not easy to place. Of those that are
figured in the text may be mentioned Rham-
phastus laematus (Fig. 67), Otis tetrax (Fig. 42),
Dendrocopus major (Fig. 68), Phalacrocorax
carbo (Fig. 51), Corvus cor ax (Fig. 76), Centurus
uropygialis (Fig. 69), Pitangus derbianus (Fig.
70) and Cariama cristata (Fig. 29).

Opaque nerve-fibres. As previously stated,
the neurilemma, or nerve-sheath, of the
opticus is in many Birds, as occasionally in
Man, continued into the retinal substance.
These nerve-fibres are easily seen in the avian
fundus when viewed with the ophthalmo-
scope, although in preserved eyeballs they are
invisible to the naked eye.

In some instances they radiate from the
nerve-head as whitish, thread-like rays, in
such a fashion as to cover the whole of a
wide area about the optic entrance. This
condition is well shown in Turdus merula
(Plate LVII), Spagolobus adratus (Plate
XLIII), Rhamphastus laematus (Plate XL VI),
Plegadis falcinellus (Plate XXIII), and Tin-
nunculus alaudarius (Plate XXXV).

As a rule, however, the avian fundus is free
of these nerve elements; in all probability
they interfere to some slight extent with
general retinal vision and are consequently
absent in those genera requiring the most
acute visual powers. They are few in num-
ber or are entirely absent in Night Birds, and
in such representative species as Gypaetus
barbatus (Plate), XXXII Casuarius occipitalis
(Plate III), Haliaetus leucocephalus (Plate
XXXIII) and Rhinochetus jubatus (Plate
XVIII).

They are short or inconspicuous in all the
acarinate birds, so far examined, including
the Tinamou (Plate V) as well as in
Nycticorax nycticorax (Plate XX), Crax glo-
bosa (Plate VI), Coturnix histrionica (Plate
VIII) and Phalacrocorax carbo (Plate XXVIII).

E. Photography of the Fundus Oculi in
Living Birds

Many attempts have been made to photo-
graph the fundus oculi through the pupil in
living subjects — to combine, as it were,
photography with ophthalmoscopy. If this
scheme is ever put into practical operation,
especially if it be found possible to photograph
the eyeground in its natural colors so that
the negative can be reproduced and published,
a great advance will be made over the re-
stricted (because slow and expensive) plan
per force adopted by the writer. Photog-
raphy of the colored details of the fundus
would render unnecessary either the expert
ophthalmologist or the trained artist, while
the number of avian backgrounds explored
by such exact methods would soon be counted
by hundreds where they are now registered by
units. Moreover, as the ophthalmoscopic
picture is to a certain extent differently inter-
preted, and correspondingly described and

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS

Fig. 60.
Amazon Parrot {Chrysotis amazonica) .

Fig. 63.
Laughing Kingfisher (Dacelo gigas) .

Fig. 61.
Lesser Sulphur-crested Cockatoo (Cacatua galerita).

Fig. 64.
Black Hornbill (Spagolobus adratus).

Fig. 65.
Nightjar (Caprimulgus europeus).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

Fig. 62.
Kakapo or Owl Parrot (Stringops habroptUus) .

THE FUNDUS OCULI OF BIRDS

Fig. 66.
European Cuckoo (Cuculus canorus).

Fig. 69.
Gila Woodpecker [Centurus (Melanerpes) uropygialis].

Fig. 67.
Sulphur-breasted Toucan (Rhamphastus lamatus).

Fig. 70.
Derby Tyrant (Pitangus derbianus).

Fig. 68.
Great Spotted Woodpecker (Dendrocopus major).

Fig. 71.
Chimney Swallow (Hirundo rustled).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

OPHTHALMOSCOPY OF THE FUNDUS IN LIVING BIRDS 47

Fig. 72.
American Mocking Bird (Mimus polyglottos) .

Fig. 75.
Blue Jay (Cyanocitta cristata).

Fig. 73.
American Bunting (Cyanospiza versicolor).

Fig. 74.
Law Bird of Paradise (Parotia lawii).

Fig. 76.
European Raven (Corvus corax).

Diagrams of the Pecten as seen by the Ophthalmoscope in Various Species of Birds.

THE FUNDUS OCULI OF BIRDS

pictured by different observers, an accurate
photographic reproduction is much to be
desired.

Probably the inventor who has come near-
est this ideal is Wolff (Monatsbl. f. Augen-
heilk., p. 447, Oct., Nov., 1907) of Berlin,
who has done much in the photography of the
human fundus. He made use of the light
furnished by the Zeiss projection apparatus,
the efferent rays being reflected into the eye,
through half the pupil, by a specially con-
trived mirror. The efferent rays passed out
through the other half of the pupil and were
focussed in a photographic camera. A circle
of the fundus about 10 mm. is thus illuminated
at one time and the resulting picture — of
course in gray tones — is magnified from three
to four diameters. The required exposure is
less than one-thirtieth of a second. The prints
showed the optic entrance, the retinal vessels

and other gross details of the eye-ground but
lacked that definition without which fundus
reproductions are of little practical value.

Stimulated by these experiments of Wolff
and by the experience of Dimmer, Thorner
and Neuhaus, the writer, in conjunction with
Dr. Earl Brown of Chicago and other experts,
has endeavored to solve the problem both of
ordinary and chromo-photography of the
avian fundus. It must be confessed that
nothing satisfactory has come of these efforts,
nor of the corresponding attempts, referred
to on p. 61, to photograph the eyeground of
prepared specimens. The main difficulty
(without entering into the details of the fail-
ures) in all these instances lies in the present
impossibility of focussing clearly at the same
instant all the points on such a concavity as
the interior of the eyeball presents, either
in its post mortem or its living state.

Chapter VII

MACROSCOPIC APPEARANCES OF THE FUNDUS OCULI OF
BIRDS IN PREPARED SPECIMENS

This subject has to some extent been dis-
cussed in Chapters IV and IX. As previous-
ly stated, the actual appearance, arrangement
and relations of the organs in the Bird's
fundus — pecten, retina, optic nerve, choroid
and choroidal bloodvessels, macular regions
(areas of distinct vision) — can be readily per-
ceived in properly preserved eyeballs. Im-
mersed in Perenyi's fluid and a series of
alcohols and otherwise carefully prepared, an
equatorial section of an avian globe furnishes
material for a satisfactory macroscopic study
of many of the parts in the interior of the eye.
The gross relations of these parts in typical
birds are seen in Figs. 1, 5, 6, 7, and 11.

The Pecten is probably always somewhat
shrunken and more or less displaced even in
the freshest and best preserved specimens;
so that allowance must be made (in examining
prepared material) for that fact. This is the
reason, perhaps, that Apteryx was for several
generations credited with absence of a pecten,
until Lindsay Johnson proved its presence in
that bird. The peculiar construction of the
small marsupium in the Kiwi not only made
it easy of reduction in volume but it was also
decidedly bleached by the alcohol in which the
(old) material was immersed for a long period
before it was made the subject of that naked-
eye examination that led to the original
error of observation.

The pecten varies in shape and size, as well
as in the number and the character of the
folds of tissue that compose it, according to
the genus to which the bird belongs. Indeed,
such a striking and varied picture does the
pecten exhibit, both when seen with the oph-
thalmoscope during life and in prepared mac-

roscopical and microscopical specimens after
death, that one might almost recognize the spe-
cies by studying this organ and its relations to
other parts of a bird's fundus. In the accom-
panying text are a number of drawings of the
avian pecten as seen in prepared eyeballs.

That the human hyaloid artery of fetal life
is a vestigal pecten seems almost self-evident.
No one who has examined a persistent hyaloid
artery and its branches, particularly if he has
been fortunate enough to see the vessels
carrying blood to and from their termination
in the vitreous, can fail to be reminded of the
structures that occur normally in some mam-
malian, most reptilian, and all avian eyes.
This arrangement surely carries us back in
fetal evolution to those sauropsidian ances-
tors who have left their mark on our em-
bryology.

Attention may be especially drawn to the
pecten of the American Coot (Fulica ameri-
cana), consisting of 15 double folds. It shows
in a remarkable and unusual fashion their
fan-like arrangement, especially at the free,
upper margin of the organ; it is there firmly
attached to the fine vitreous processes and
the hyaloid membrane. See Fig. 84.

In Gadow's contribution to Bronn's Tier-
Reich a list of the number of convolutions in
certain Birds is given, and reference is made
to an attempted classification of Aves based
upon it.

The optic disc, viewed macroscopically, is
generally seen as an oval, ovoid, sometimes
almost round, white or yellowish-white area
largely obscured by its union with the base of
the pecten. Its long diameter is generally
from two to three times its width.

[49

THE FUNDUS OCULI OF BIRDS

Fig. 77.

Nubian Ostrich
(Struthio camelus) X3.

Fig. 78.
I
I Martinets Tinamou

(Rhynchotus rufescens) XlO.

Fig. 79.

Valley Partridge or Quail (Lophortyx californicus
vallicola) X16.

Fig. 80. "-----__

British Wood Pigeon (Columba palumbus) X 10.

Fig. 81.
Wonga Wonga Dove (Leucosarcia picata) X 10.

Fig. 82.
Pigeon Guillemot (Cepphus colnmba) X9.

Lateral View of the Pecten in the Prepared Eyes of Certain Species of Birds.

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS

Fig. 83.
European Crested Grebe (Podicipes cristatus) X 12.

Fig. 84.
American Coot (Fulica americana) X 12.

Fig. 85.
Dark-bodies Shear-water (Puffinus griseus) X9.

Fig. 86.
Herring Gull {Larus argentatus) X 7.5.

Fig. 87.
Greater Yellow Legs {Totanus melanoleucus) Xll.

Fig. 88.
Hudsonian Curlew (Numenius hudsonicus) X 12.

Lateral View of the Pecten in the Prepared Eyes of Certain Species of Birds.

THE FUNDUS OCULI OF BIRDS

Fig. 89.
Black-bellied Plover (Squatarola squatarola) X9.

Fig. 90.
Great Bustard (Otis tarda) X5%.

Fig. 92.

Black-crowned Night Heron (Nycticorax nycticorax
ncevius) X6.

Fig. 93.
Lesser Snow Goose (Chen hyperboreus) X9.

Fig. 94.

Fig. 91.
American Bittern (Botaurus lentiginosus) X8.

Lateral View of the Pecten in the Prepared Eyes of Certain Species of Birds

Common (Old World) Flamingo (Phoenicopterus
roseus) X8.

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS

Fig. 95.
Brandt Cormorant (Phalacrocorax penicillatus) X9.

Fig. 96.
Tawny Owl {Syrnium aluco) X7.

Fig. 97.
European Barn Owl (Strix flammea) X9.

Fig. 98

/ Greater Sulphur-crested
' Cockatoo (Cacatua galerita) X 9.

Fig. 99. *- — - -

Common (British) Kingfisher
(Alcedo ispida) X 18.

Fig. 100.
Common Hoopoe (Upupa epops).

Lateral View of the Pecten in the Prepared Eyes of Certain Species of Birds.

THE FUNDUS OCULI OF BIRDS

Fig. 101.
Anna Hummingbird (Calypte annae) X31.

Fig. 102. "\_.

Yellow-billed Cuckoo
(Coccyzus americanus) Xl2.

Fig. 104.
Red-shafted Flicker (Colaptes mexicanus).

Fig. 105.
Western Mockingbird (Mimus polyglottos leucopterus).

Fig. 103. *---.__^

Red-headed Woodpecker (Melanerpes erythrocephalus).

Fig. 106.
Bluebird (Sialia sialis) X 18.

Lateral View of the Pecten in the Prepared Eyes of Certain Species of Birds.

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS

Fig. 107.
California Shrike (Lanius ludovicianus gainbeli) .

Fig. 108.
American Crow (Corvus americanus).

Fig. 109.
Steller Jay (Cyanocitta stelleri) X12.

Lateral View of the Pecten in the Prepared Eyes of
Certain Species of Birds.

The Retina and the vessels of the choroid are
practically invisible in the eyes of birds viewed
macroscopically a few minutes after death.
However, when treated with Perenyi's fluid
and other preservatives or especially in case of
successful carotid injections, the choroidal
bloodvessels and tissues become more opaque
or at least more translucent and may then be
studied with success. Doubtless the oph-
thalmoscope gives us the one best means of
seeing these tissues as they exist during life,
but both methods, supplemented by the mi-
croscope, are needed for a complete study of
them in all their relations. Very little light is
thrown on these questions by naked-eye ob-
servations of the choroidal vessels, although in
some birds, especially when injections of car-
mine have been made, they are quite evident.
Serial sections, in conjunction with the use of
the ophthalmoscope, afford the best means
of studying these fundal vessels.

The pigment deposits and other histological
elements in the choroid and retina — espe-
cially in the former — that combine to make
or modify the general coloration of the fundus
oculi are best seen with the ophthalmoscope;
prepared specimens furnish but slight indi-
cations of these. Differences of level, as in
the macular areas, are, however, well shown
macroscopically.

Areas of Distinct Vision. As a result of
the investigations of Slonaker and the writer
it may be said of Birds with but a single
fovea that this sensitive area is generally
placed about the center of the retina, slightly
above and towards the nasal aspect of the
optic nerve entrance. This observation is
practically illustrated in a number of pictures
reproduced in this work from the drawings of
Kennedy and the paintings of Head. See,
for example, the drawings of the fundus views
of Sialia sialis (Fig. 140), Corvus americanus
(Fig. 142) and Nycticorax nycticorax (Fig. 129),
in which a single, deep, well-defined fovea is
present.

An exception to the rule of the nasal posi-
tion of the single fovea? and macular regions is
noticeable in the Owls. These birds possess
a single, deep fovea encircled by a round,
sharply defined area located above and on

THE FUNDUS OCULI OF BIRDS

the temporal side of the optic disc, an example
of which is pictured in Syrnium aluco (Fig.
132) and Strix flammea (Fig. 112). This ar-
rangement closely approaches the binocular
maculae of Man; indeed the visual apparatus
of Strigiformes resembles the human eye
more closely than does any other order.

The Choroid is seen macroscopically as a
dark background for the translucent, or only
partially visible retina; indeed, the coloration
of both macroscopic and ophthalmoscopic
pictures of the bird's fundus is largely deter-
mined by this deeply pigmented ocular tunic
with its rich vascular supply.

As noted in Chapter VIII, domestication
brings about changes in all the fundal tissues
— usually tissue degeneration, if not actual
disease. Hence we find that Gallinse possess
very shallow or doubtful fovea?. The writer
has concerned himself little with barnyard
fowls, but Slonaker has shown that while
Columba livia domestica, still retains a medium
fovea surrounded by a well-defined macular
area, Meleagris gallopavo and Numida pucher-
ani have very shallow arex centrales. As
stated elsewhere, some Birds have no macular
region demonstrable by the naked eye. Gallus
domesticus, for example, has an extremely
doubtful fovea, while Anser domesticus and
Anas boschas domesticus, in addition to a very
shallow macular region, exhibit a band-like
area extending horizontally across the retina.
The latter device probably enables the bird
to widen the limits of his field of distinct
vision (especially while feeding) without being
obliged to move the whole head. This curi-
ous provision is more clearly shown in the
Ring-Neck Plover whose fundus shows a
very distinct band-like area that passes
obliquely across the retina. A dark fine,
like a trough or gutter, appears to the naked
eye in preserved specimens to extend almost
the full length of the band. Slonaker ex-
mined this area microscopically but could find
no trough-like depression.

Oval, ovoid, circular or ribbon-like areas,
are as a rule, readily traced in the gray,
smooth retinal tissues, although both the
microscope and ophthalmoscope may be
needed, as in the Flamingo and some of the

Gallinaceous birds, as a supplement to macro-
scopic inspection to decide the presence or
otherwise of a macular region or of any of
its components. The limits of the retinal
band area often call for these aids; indeed it
may be said that no exploration of an avian
fundus should be regarded as complete until
all these requirements are met. Areas of
acute vision, in prepared material, appear to
be whiter or less gray than the surrounding
retina; there is not, however, a sharp defini-
tion to the naked eye, or even when observed
by the help of a magnifying lens, but the tis-
sues of the arem centrales shade off and gradu-
ally blend with the perimacular tissues.

It must not be assumed that because no
central area of distinct vision is discovered
macroscopically that it does not exist. Some
macular regions are so shallow and so slightly
differentiated from the neighboring tissues
that only the microscope can settle the ques-
tion of their existence.

The exact character and visual purpose of
these retinal band-like areas (sometimes also
visible to the ophthalmoscope) await further
histological investigation.

Birds of prey as well as the swift fliers show
the best marked and the greatest variety of
macular regions. A typical instance is seen
in the Sparrow Hawk. In this bird each
fundus presents a well-marked fovea nasalis
and fovea temporalis connected by a short
band-like area.

The nasal fovea is invariably the deeper and
sharper of the two, and probably is used when
distinct sight and binocular vision are required.
It is surrounded by a large, macular area and
is situated about the center of the retina.

The temporal fovea is shallower, is encircled
by a smaller area and is placed near the
periphery of the retina lower than the nasal
fovea but about the same distance from the
optic papilla. This foveal region holds about
the same relative position in the fundus as
the single fovea of the Owl while the fovea
nasalis stands in the same relation as that
occupied by the Blue-Bird and the Robin.

Of the swift fliers the Terns and the Swal-
lows present much the same foveal and band-
like sensitive regions as the Hawks; in other

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS 57

Fig. 110. Example of the First Type of Central Visual Arese in Birds. The Amacular Fundus of the
California Valley Quail (Lophortyx californicus vallicola) X16.

Fig. 111. Example of the Second Type of Central Visual Arese in Birds. The Nasal Monomacular
Fundus of the Steller Jay (Cyanocitta stelleri) X 12.

THE FUNDUS OCULI OF BIRDS

Fig. 112. Example of the Third Type of Central Visual Area; in Birds. The Temporal Monomacular
Fundus of the European Barn Owl (Strix flammed) X9.

Fig. 113. Example of the Fourth Type of Central Visual Area? in Birds. The Bimacular Fundus of

the British Kingfisher (Alcedo ispida).

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS

words the disposition of the areas for acute
vision assumes this form in Birds that take
their prey on the wing or by darting upon it
from a distance.

A Classification of Areas of Distinct Vision
in Birds

From the foregoing it may be concluded
that there are at least six arrangements of
these areas, and consequently six forms of
apparatus for securing acute eyesight in birds.
These may be classified as follows:

1. The amacular fundus, in which, as in
the California Valley Quail (see Fig. 110),
there is to be seen neither with the ophthal-
moscope nor in preserved material any indica-
tion of a central macular region; rather a rare
class. It is only by a microscopical examina-
tion of serial sections that one sees the his-
tologic elements indicative of an area of
vision more specialized for distinct visualiza-
tion than the surrounding retina. Such fundi
are rare, and are found, for example, in a
few domestic birds. Slonaker discovered a
shallow and ill-defined central area in the
Turkey (Meleagris gallopavo) and the Guinea
Hen (Numidia pucherani); also "a very
slight thickening," instead of a fovea, in the
Cock (Gallus domesticus).

2. The nasal monomacidar fundus, situated
in the centre of the retina, is found in the
majority of birds. An example is shown in a
drawing of the eyeground of the Steller Jay (see
Fig. 111). As a rule, it is best demonstrated
macroscopically, although even a cursory ex-
amination of the colored plates in this work
will reveal numerous examples of this form of
fundus when viewed ophthalmoscopically.

3. The temporal monomacidar fundus is
found almost exclusively in the Owls. An
example of this form is seen in the European
Barn Owl (Fig. 112); indeed in all the Strigi-
formes whose fundi are pictured or described
in this monograph.

4. The bimacular fundus, in which there
are two macula?, generally a deeply marked
and principal nasal region and a subsidiary
temporal area. See Fig. 113, representing a
macroscopic view of the (preserved eyeball)
fundus of the Belted Kingfisher.

There are two sub-varieties of this fundus;
(a) certain eyes of regular form in which the
nasal macular region is well developed and
the fovea is deep and sharply defined, as in
Alcedo, Sterna and Tachycineta; (b) in birds
with eyes of irregular shape, exhibiting a
deeper temporal fovea and better marked
macular region. These are found in the
Hawks especially.

5. A band-like central area with which is
almost invariably associated a well-defined
fovea or macula. To this form of avian back-
ground the writer has given the name infula-
macular* fundus. As an example, see Fig.
114, showing a macroscopical view of the eye-
ground in the Greater Yellow-legs (Totanus
melanoleucus) . In this class the band in-
closes, in some part of its course, the single
fovea which in its turn is found on the nasal
side of the fundus.

6. Finally, in some avian backgrounds
there are two macular regions, either joined to or
associated with the band-like area, to which the
name infulabimacular fundus has been given
by the writer. An ocular background of this
description is seen in the Common Flamingo.
See Fig. 115. There are at least two varieties
of this form.

The Sparrow Hawk (Falco sparverius) and
Buteo borealis furnish examples of form (a) —
a well-defined nasal macula with a deep fovea
situated near the centre of the retina and a
shallow though easily demonstrable temporal
macula, the two joined by a short ribbon-
like area. The band area does not extend
beyond either macular region.

In second form (b), represented by the Tern
(Sterna hirundo), the band-like area encloses
a nasal macula while a second (temporal)
macular region lies above and apart from
these.

Even a slight acquaintance with the fundi
oculorum of the comparatively few Birds so
far examined shows not only numerous types
of areas centrales, but a still greater variety in
their size, shape and appearance, both mac-
roscopical and ophthalmoscopical. These are
most distinctly marked in the prepared speci-
mens. Some Birds exhibit a large, circular
*Infula, a band or ribbon.

THE FUNDUS OCULI OF BIRDS

Fig. 114. Example of the Fifth Type of Central Visual Arese in Birds. The Infulamacular Fundus

of the Greater Yellow-legs (Totanns melanoleucus).

Fig. 115. Example of the Sixth Type of Central Visual Arese in Birds. The Infulabimacular Fundus
of the Common Old-world Flamingo (Phoenieopterus roseus).

FUNDUS OCULI OF BIRDS IN PREPARED SPECIMENS

area — single or double, sometimes associated
with a band area, sometimes not — with clearly
outlined margins and a deep fovea and dis-
tinct foveola. In others the fovea is shallow
and the macular borders are with difficulty
differentiated from the fundal retina.

Photography of the Fundus Oculi in
Prepared Eyeballs

Attempts similar to those of Wolff and
others, mentioned in Chapter VI, to photo-
graph the interior of the posterior half of the
eye have been made with some success in the
case of prepared eyes. The difficulties that
surround these attempts, although fewer than
with the living subject, are as yet unsur-
mounted so far as minute and exact fundal
details — the chief object to be attained —
are concerned. Photography furnishing a
clear and sharp definition of small objects
arrayed at various points in one concave sur-
face is as yet impossible — hence the blurred
appearance of pictures of the vertebrate eye-
ground so far published. Even the best of
these — the enlarged stereoscopic photo-
graphs that illustrate Arthur Thomson's
Anatomy of the Human Eye (London, 1912),
the carefully prepared original photographs
in the beautiful atlas of Fritsch, and the
stereographs of George Dixon — hold out
little hope that similar processes may be of
use in depicting avian eyegrounds. Only
the laborious pen and brush of the careful
and competent artist-ophthalmoscopist can
so far be depended upon to depict the mac-

roscopic appearances of these complicated
tissue arrangements.

R. H. Elliot (The Lancet, p. 830, Nov. 11,
1916) has developed a method of photograph-
ing prepared eye specimens of which the
writer has had no personal experience, but
which he believes may be of value to the
investigator. Elliot regards the following
points of importance: The photograph must
be taken in water, without the intervention of
glass or other similar material. The source
of light must be good and even. The camera
must be placed vertically above the object
so as to avoid reflections. The object of the
photograph must be placed so that its image
will occupy the center of the plate, and a
method of adjustment should be available to
secure this end with a minimum of incon-
venience. A simple arrangement is neces-
sary to fix the eye in position during the
whole period of exposure. To save unneces-
sary retouching the object should be photo-
graphed lying on a dark and uniform surface
to obviate the background disturbing the
attention of those viewing the picture. Care
should be exercised in the choice of a camera
and exposure periods must be carefully
studied. For the making of lantern-slides
the contact method was recommended, and
attention was directed to the following points :
correct exposure; the preparation of plates
for exposure; development and fixation of
the slides; the drying of the plates; and the
reduction, intensification and varnishing of
slides.

Chapter VIII

EFFECTS OF DOMESTICATION AND OTHER ABNORMAL

INFLUENCES ON THE FUNDUS OCULI OF

WILD SPECIES OF BIRDS

As noted in Chapter III the eyes of only
healthy individuals and (as far as could be
ascertained) of normal wild species have been
chosen for the purposes of this research. In
practice, however, this is not as easy a task as
first appears, since it is on occasions difficult
to decide by any or all of the three principal
means of investigation — the ophthalmoscope
in living specimens, the microscope and naked
eye in preserved globes — whether a given
condition is normal or abnormal, congenital
or acquired. The writer's observations of
the eyes of both domestic and wild birds leads
him to believe that domestication of Birds,
which generally means a radical departure
from their natural food, exercise, manner of
raising their young, use of their various or-
gans (eyes included) and above all the effects
of confinement per se, is the principal cause of
the anomalies seen in the fundi of caged or
barnyard species. This difficulty in deter-
mining the exact character of tissue altera-
tions is all the greater when the suspected
fundus change occurs in both eyes and the
organs are not available for macroscopic and
microscopic examination. For instance, the
eyeground of the Spoonbill (Plate XXV) is
shown with a curious (and unusual) linear
stripe running parallel and close to the optic
disc. This may be an abnormal fundus con-
dition although the weight of evidence leans
the other way.

Nocturnal birds, when caged, appear to be
especially affected by "Zoo" conditions.
The Caprimulgidae, as well as the Strigi-
formes, for example, are liable to acquire
choroidal diseases.

While examining a number of common
Screech Owls, the writer found one individual,
about five years old and three years in captiv-
ity, that showed the following conditions:
Left eye; usual Owl fundus; well marked
disseminated choroiditis, affecting the nasal
aspect of the background more than the tem-
poral. The choroidal vessels show through a
number of atrophic areas. Usual pigment
spots smaller than normal, almost punctate.
Right fundus : the general appearance on this
side is of a striped gray, very much like the
warp and woof of some fabrics, or like the begin-
ning choroidal atrophy of myopia. In other
respects the right fundus resembles the left.

Mr. Head informs me that in examining
with the mirror a Bluebird (Sialia sialis) in
captivity seven years, the vitreous humour
was found to be quite dull and foggy and the
fundus showed spots of an orange-red color.
This was very likely a diseased condition, as
the other eye had a cataract in it.

The writer has examined with the ophthal-
moscope the eyes of a number of Turkey
Vultures (Cathartes aura), practically domestic
animals in many American towns, and found
few of them healthy. In one case the bird
had cataract in each eye. In another there
was beginning central opacification of the
lens in the left eye; the same condition more
advanced in the right. A third had no len-
ticular changes, but owing to a suspicion that
the fundus findings might not be those of a
healthy individual the findings were not in-
cluded in the list described in Chapter IX.
The following are the notes of this examina-
tion: Left fundus; general coloration steel

[62]

EFFECTS OF DOMESTICATION ON THE FUNDUS OCULI

gray. Resembles the Bald Eagle. Pecten
large and apparently reaches posterior part of
lens. Optic nerve entrance entirely obscured
and optic nerve fibres are persistent at tem-
poral margin of the disc. Retinal reflexes
very distinct. At the upper and temporal
edge of the disc the white border of papilla
shows quite distinctly. Pecten very black
and in no part translucent; lies in well defined
coil-like folds. No definite visual areas can
be differentiated from the general fundus.
Fundus 'granular' in places. The refrac-
tion slightly hyperopic.

Beginning with his experience as a student
in the Thierartzneischule of the University of
Berlin in 1888, the writer has examined the
eyes of many barnyard fowls, to find in them a
great variation in the fundus appearances even
of the same species. The following few de-
scriptions from notebooks will suffice to illus-
trate this point:

Bantam cock (Gallus domesticus). Fun-
dus examination; direct, with electric ophthal-
moscope. Both backgrounds the same. The
whole eyeground is of a uniform 'pepper and
salt' and granular variety — the 'pepper'
predominating. The macular region shows
quite plainly, the fovea being represented by a
single star-like deposit which looks exactly
like (and may be) a crystal of cholesterin.
The disc is a long oval, almost but not en-
tirely covered by the pecten at each side but

quite clear at either end. The pecten changes
size and position under the examination but
not so quickly as in the Crow, for example.

Large and mature 'speckled hen,' with a
light, brick-red iris. Kept in laboratory of
St. Luke's Hospital as a source of pure avian
blood. The observations on the bantam
rooster just detailed almost entirely coincide
with the findings in this bird, except that no
single stellate formation in the macular region
was noticed. Skiascopy and pupil reflexes
almost the same. There was no noticeable
astigmatism developed in either.

A great variety of fundal pictures — nor-
mal and abnormal — are presented by our
Domestic Pigeons. The following are notes
on the fundi of the Homing or Homer Pigeon :
The background is readily seen in all these
domestic Pigeons. It bears a close resem-
blance to that of the common Hen, except
that the macular region is better defined in
the Pigeon. The sprinkling of fine, dark-
brown pigment over a reddish background,
interrupted here and there with colored points,
generally yellowish and glittering, giving
the whole a uniform appearance like fine
'mixed tweed' cloth seen from a distance of
a few feet, is very characteristic of this class
of fundi. The pecten is relatively small,
clubbed, spiral, black-brown and prevents
one from seeing more than a third of the
ovate disc.

Chapter IX

THE OPHTHALMOSCOPIC AND MACROSCOPIC APPEARANCES
OF THE FUNDUS OCULI IN VARIOUS ORDERS OF BIRDS

That one may properly answer many questions
involved in the anatomy and physiology of the
important organs and tissues that constitute
the eyeground in Vertebrates it is necessary to
consider not only the ophthalmoscopic, but the
macroscopic and, in some instances, the mi-
croscopic findings. Although none of these
methods of research has as yet been carried out
with any approach to completeness yet the his-
tology of the retina and other visual organs has
been satisfactorily studied in Man, and a few
other species of Vertebratse, by Cajal, Greeff
and others. Little attention has, however,
been paid to the other two forms of investiga-
tion, that is to avian ophthalmoscopy or to what
may be termed avian ophthalmomacroscopy.

Ophthalmoscopy is, in effect, a demonstra-
tion of the actual (comparative) size and rela-
tive position of the principal parts — nerves,
bloodvessels, [oil droplet (?)] dots, organs of
special sense — as well as the actual coloration
of the fundus oculi of the living Bird. Macro-
scopy, on the other hand, reveals some details
of the Bird's eyeground not apparent or only
faintly apparent to the ophthalmoscope. For
example, the extent and other exact relations
of some of the areas of acute vision, as well
as definite, lateral views of the pecten, are
better determined by naked-eye examinations
of prepared specimens than by viewing them
through the pupil of animate species.* To

*The dots that besprinkle the fundus in the black
and white drawings (to indicate the macroscopical
appearances of the fundus in preserved specimens) are
merely the artist's device to depict the concavity of
the eyeball, elevation of parts, etc., and have nothing
to do with the f undal dots and other coloration so well
shown in the colored plates.

this may be added, as elsewhere pointed out,
that in certain instances the fine anatomy and
exact relations of certain organs and tissues of
the background of the Bird's eye can be deter-
mined only by a microscopical examination of
stained and injected sections of the parts.

The following species (healthy adults) have
been examined either with the ophthal-
moscope or by inspection of prepared eye-
balls, or by both methods. In a number,
also, the eyes have been sectioned and ex-
amined microscopically. These findings have
been mostly pictured in the text or by ap-
pended colored plates, and will now be
described.

A. RATITAE

Struthioniformes

Nubian or Northern Ostrich. Struthio
camelus. (Figs. 116 and 77; macroscopic
view). The black and white drawing of this
fundus shows a large, regularly oval papilla
sprinkled with pigmented dots and circled by
a well-defined border.

The foreshortened view of the pecten gives
one the impression of an octopus-like figure
lying upon and almost covering the surface of
the optic disc, which is plainly visible beneath
and sprinkled with pigment dots. There are
readily counted twenty-four pectinate con-
volutions (12 double folds) that meet above
and are joined to an irregularly ovoid body —
the crest or free margin of the marsupium —
apparently by a sort of purse-string action.
The folds of the pecten are extremely thin and
entirely unlike the great majority of the con-
volutions in carinate birds.

[64J

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

Fig. 116. Nubian Ostrich (Struthio camelus) X3.

Fig. 117. Rufous Tinamou (Rhyncotus rufescens) XlO.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS OCULI OF BIRDS

A long, uniform band of two dark lines
enclosing a broader white band runs almost
horizontally across the fundus above the
optic disc. About the middle point of the
band (above the disc and towards the nasal
aspect of the fundus) is a round depression
(?), black in the center and surrounded by two
indistinct, pigmented semicircles, made by a
widening of the parallel lines that enclose the
fundal band.

The extended major axis of the optic
entrance oval describes an angle of almost
45° with the inferior border of the retinal
band.

This angle the writer has called the infula-
papillary angle, from infula, a band, and pa-
pilla, the optic disc.

Plate I, page 121, gives a very good
idea of the ophthalmoscopic appearances in
this species. It represents the eyeground as
seen in specimens examined by Head in the
Gardens of the British Zoological Society and
by the writer in a young male adult living in
the open and under ideal conditions on the
Cawston Ostrich Farm near San Diego, Cali-
fornia.

The general color of the eyeground is dull
red, varied by a uniform sprinkling of lighter
red, round dots and gray granules. The
lower half of the fundus appears somewhat
grayer in tone than the upper sectors. This
appearance is probably due to the numerous
opaque nerve-fibres that extend from all
sides of the papilla as a center across the fun-
dus to the periphery of the ocular background.
The red coloration of the fundus is seen to be
more intense towards the upper half of the
eyeground. The optic nerve-entrance is very
broad, oval in shape, and its contour resembles
that of Rhea and the Tinamous. The mar-
gins of the nerve-head are very white and it
is possible with the mirror to see all around
the pecten. The centre of the disc, including
the parts near the root of the pecten, is
stippled with minute, brown pigment dots,
like black pepper grains.

The pecten proper rises from the nervehead
much like the same organ in the Tinamou,
and presents, ophthalmoscopically, the ap-
pearance of a number of dull, dark, sepia-

brown tubercles. It does not project far
forward into the vitreous cavity, while its
outlines and contour may be distinguished
both above and below the disc. The pectin-
ate margins are formed of round or ovoid pro-
jections. These nodular masses also appear
to constitute the body of the pecten.

The macula is situated about as it is in
Rhea; it is not very striking in appearance,
and takes the form of a crescentic arrange-
ment of minute, gray dots. It is seen towards
the nasal side of the disc near its upper end,
and is not surrounded by the closed reflex-
ring noticed in so many avian fundi.

Rheiformes

American Ostrich. Rhea americana.
For an exact reproduction in color of the
ocular background of this bird see Plate II,
page 121, which shows the left eye; erect
image.

The coloration of the fundus as a whole is
buff, merging into dull red at the periphery.
It is stippled all over with minute dots of
a lighter tint, and much resembles the fun-
dus appearances of the Tinamou shown in
Plate V.

The optic disc appears to be a broad oval,
made up of white and coarse nerve bundles
that exhibit a faintly defined, fringe-like mar-
gin all around its periphery. Radiating for a
distance of about two disc-breadths across
the fundus are a few, dull-gray, opaque nerve
fibres that finally disappear into the back-
ground.

The macula is situated slightly above and
to the nasal side of the optic papilla. It is
somewhat grayer than the surrounding eye-
ground; above, towards the outer side and
below the fovea, are a few pale, bright-green
reflex lines.

The pecten is a massive organ with saw-like
margins, the serrations being of a lighter
brown than the central body. The lower
part of the pecten is somewhat club-shaped,
and comes well forward toward the posterior
capsule of the lens. Between the projecting
teeth of the pectinate serrations may be seen
a slight stippling of pigment-like black pepper
grains.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

Casuariiformes

Westerman Cassowary. Casuarius

occipitalis. The colored drawing shown on
Plate III, page 123, is intended to reproduce
an ophthalmoscopic view of the right eye by
the erect image. Two birds (four eyes)
furnished almost identical pictures.

The fawn-colored eyeground is covered with
a minute, silver-gray stipple, in the form of
fine, short lines with their long axes running
in a vertical direction. As these dotted lines
approach the macular region they become
more and more convergent until they form a
brilliant cluster at the fovea. There is no
visible line of demarcation or reflex ring
separating this area from the general fundus
area. There are no visible choroidal blood
vessels or opaque nerve fibres.

The optic disc is long and boat-shaped,
with a reddish, apparently concave centre.
It is uniformly sprinkled with darker red
dots, which, as they approach the margin
of the papilla, are more closely packed, and
give the appearance of a shadow cast all
about the inner edge of the disc. The
margins of the nerve-head are distinctly
white, but they have not the "fibrous"
appearance seen in most avian backgrounds.

The chocolate-brown pecten, much broader
at its base than at the apex, resembles a
corkscrew, its lateral elevation being not
unlike a cockscomb, with its six serrations
rounded off at the apex. Two central serra-
tions come well forward towards the lens.

Apterygiformes

Mantell Apteryx. Apteryx mantelli.
In July, 1914, the writer examined a Mantell
Apteryx in the London Zoo. The animal
was 12 years old and probably had monocu-
lar vision. The keeper said that (in daytime
especially) the bird had poor eyesight for
both distance and near. The bird's re-
fraction was by skiascopy myopic (about
1.50 D.) in either eye. The fundus appear-
ances are exactly as Head has depicted
them in his drawing (Plate IV). In this
fundus picture the macular region is plainly
visible; and the pecten comes well forward and
is also easily seen. The ocular back-ground is

uniformly orange-red, somewhat mottled with
brown. The brilliant, white, round disc is sur-
rounded by short, opaque nerve-fibre layers,
not entirely covered by the fenestrated base
of the long, large and conical pecten, whose
pointed end reaches almost to the lens. There
are no signs of choroidal bloodvessels.

Tinamiformes

Rufous Tinamou. Rhyncotus rufescens.
(Figs. 117 and 78). A macroscopic picture
of the background shows a slight and rather
uniform pigmentation, darker towards the
periphery.

The long, narrow comb-like pecten some-
what resembles, when seen from before back-
wards, a small crayfish. It is made up of
from 48 to 50 convolutions, the dorsal crest
forming an irregular triangle with a short
spine projecting from its inferior end.

The macula is plainly marked above and
on the nasal side of the pecten, about half a
discdength from the anterior terminal of the
papilla.

Martineta Tinamou. Calodroma elegans.
A picture of the left ocular fundus (by the
erect method) is furnished by Plate V,
page 125. This taxonomically interesting
species presents a background whose colora-
tion is, in the main, a deep gray, the lower
half merging into dull orange. The whole
of the fundi is covered by a collection of
tiny dots packed closely together. In the
upper half of the field they are white, but
from the region of the disc and downwards
they become a dull orange color. Crossing
the fundus and running vertically on either
side of the papilla are several orange-red
choroidal capillaries.

The macula appears as a dull-gray area,
with a brilliant white central spot surrounded
by a small, pale-green, streaked, reflex ring.
It is plainly visible on the nasal side of the
pecten. The optic nerve entrance is oval
in shape and exceptionally broad.

The mass of the pecten almost completely
covers the optic papilla, which is quite white
and looks like a mass of coarse opaque
nerve fibres. The optic margins are bor-
dered with gray pigment, from which spring

THE FUNDUS OCULI OF BIRDS

a few short opaque nerve fibres. The pecten
is chocolate brown, and in addition to its
massive appearance is much shorter than
the same organ in most of the birds examined.
All parts and all details of this pecten can be
viewed with the mirror without the least
difficulty. It is easy to see that it is fringed
all around with pointed tabs, that the central
portion or ridge is serrated and that it comes
well forward towards the lens. In examin-
ing the fundus with the ophthalmoscope
through the undilated pupil the pecten seems
to fill the pupillary area so that most of
the fundus is obscured and shows through
the fringe about the papilla as a light shines
through a grating.

CARINATAE

Galliformes

Yarrell Curassow. Crax globosa. The
fundus appearances of this bird are depicted
as Plate VI, page 125, and are the result
of an examination of four eyes in two speci-
mens. The four backgrounds were found
to be identical in all respects.

The eyeground is a dull, leaden gray
covered with tiny, white dots. There are
no visible choroidal vessels.

The papilla appears as a long oval, whose
central zone is dull-orange mingled with
minute, dark-brown dots. It also presents
a marginal fringe of white. A few opaque
nerve fibres extend on either side of the
disc across the fundus, but for a short dis-
tance only.

The pecten, of spiral form, is colored dark
chocolate-brown. It seems to taper quite
decidedly where it joins the disc, and looks
like the roots of a tree at its distal end,
where the rootlets bury themselves in the
disc. Just above the disc, some little dis-
tance to the nasal side of the pecten, is a
round, gray, softly outlined area near which
is seen a well-marked reflex of a pale blue-
green tone.

Brush Turkey. Catheturus lathami.
Plate VII, page 127 depicts an ophthalmo-
scopic view of this species.

The eyeground is dull, slaty gray, under-
lying numbers of fine, light-gray dots. These
dots are uniformly scattered over the fundus
except towards the nasal side. Here, on a
level with the superior end of the optic
nerve and in the direction of the macular
area, they are brilliant white, are closely
packed together and are devoid of a reflex-
ring.

Extending from either side of the optic
disc and running at right angles to that
organ are a few, rather fine, semitranslu-
cent nerve fibres, which are lost towards
the periphery.

The optic disc, whose upper end is shaped
like the sharp bow of a boat, appears to be
composed of a mass of brilliant, white, opaque
nerve fibres.

The pecten, of the usual chocolate brown
color, is massive and somewhat club-shaped.
It extends well forward towards the lens
and tapers rapidly as it approaches the
superior end of the nerve.

California Valley Quail. Lophortyx
californicus vallicola. (Figs. 110 and 79.) An
examination of this background with the
naked eye discloses no well-defined macular
region, at least not in this specimen; it may
be that in better preserved material a shallow
fovea can be isolated. The pecten presents
anteroposteriorly an elongated, acuminate
figure with 30 convolutions, or 15 folds,
regularly disposed on either side of a straight,
linear, median crest, that runs the whole
length of the upper aspect of the free border.
The convolutions are separated at several
points, especially near the middle, so that
glimpses of the dotted, whitish optic entrance
beneath may be seen.

Harlequin Quail. Coturnix histrionica.
The remarkable fundus of this bird, viewed
with the ophthalmoscope, is portrayed as
Plate VIII, page 127, of this monograph.
The picture is the result of an examination
of several individuals, all exhibiting identical
eyegrounds.

The general color of the ocular background
is light gray sprinkled with minute granules,
which give it the appearance of a rough
surface. This granular surface appears

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 69

Fig. 118. Wonga Wonga Dove (Leucosarcia picata) XlO.5.

Fig. 119. British Wood Pigeon (Columba palumbus) XlO.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS OCULI OF BIRDS

white or light gray when directly illuminated
with the reflected light of the ophthalmo-
scopic mirror.

The optic nerve-head gives one the visual
impression that it is formed of brilliant,
white, short, coarse, opaque fibres. Its
shape is unusual, being long and narrow,
with a rather striking resemblance to the
projecting, serrated jaws of the Sword Fish.
Extending along each side of the optic disc,
at right angles to it, are a few rather pale,
thin, opaque nerve fibres.

The pecten is lighter brown in color than
usual, and is very narrow at its junction
with the papilla. On either side of it are a
few minute dots of brown pigment. The
inferior segment of the pecten forms a cor-
rugated, bulky mass which, however, ex-
tends well forward into the vitreous cavity
to the posterior surface of the lens. No
definite macular region was discovered in the
various specimens examined.

Columbiformes

Wonga Wonga Dove. Leucosarcia
picata. (Figs. 118 and 81 ; macroscopic views.)
The retina in the eyes of the one specimen
examined showed an unusually smooth
membrane.

The long, narrow pecten resembles the
"comb" of the Wood Pigeon, and projects
into the vitreous like a house-heating radia-
tor with about 19 coils, forming 38 (or
more) convolutions in all. The ridge-like
crest conceals the upper middle line of the
pectinate mass which, in its turn, entirely
obscures a view of the optic entrance. The
lower free border of the marsupium appears
as a broad parallelogram covered with pig-
ment grains, contrasting sharply with the
superior end, which comes gradually to a
rounded point.

There is no well-defined macular or foveal
area.

As shown in Plate IX, page 129, the
ocular background of this species presents,
when examined by the ophthalmoscope, a
uniform, gray tint. White dots, lighting up
the fundus, are scattered over the entire field.
A few choroidal capillaries are to be seen.

The optic disc forms a long oval; it ap-
pears as if it were composed of a collection
of white fibres, and these seem bunched to-
gether for about one-half the length of the
pecten. Opaque nerve fibres radiate from
the circumference of the papilla, while sev-
eral orange-red (choroidal) vessels, inter-
spersed with pigment dots, run on either side
of it.

The pecten appears as an exceptionally
long, corrugated, dark-brown mass. Seen
through the mirror from above it has the
appearance of a piece of tarred rope.

The macular area is seen to the inner
side of the disc and a little above its upper
end. The sheen of the pale-green reflex
that plays about it when illuminated by the
light of the ophthalmoscope looks like
watered silk. The fovea has the appearance
of a small green flare, something like that
from a bull's-eye lantern seen close at hand.
Only one macula can be seen.

British Wood Pigeon. Columba palum-
bus. (Figs. 119 and 80; macroscopic views.)
The background of this species shows an
elongated, pointed, ovoid pecten, made up of
closely fitting plications (about 34 in number)
joined in a free upper margin. The main
body of the pecten is not concealed, as it
usually is, by the crest or line of junction
above, which has an abrupt flattened appear-
ance below, an acute sloping termination
above.

A faint and doubtful foveal depression is
noticeable above and slightly to the nasal
side of the disc in some specimens examined
but this area does not show plainly in the
individual here pictured.

The ophthalmoscopic appearances in this
species are depicted in Plate X, page 129.

The general tint of the ocular back-
ground, as seen by the erect image, is pale
slate-gray. The eyeground is covered with
very small, dull-white dots so that the whole
fundus presents a lighter shade of gray
than it otherwise would. On the lower
half and each side of the optic disc are
seen several orange colored choroidal blood-
vessels, which become more numerous as one
approaches the periphery. Extending at

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

right angles to the papillary margin are a
few opaque nerve fibres.

A little above the superior end of the
optic nerve-head and towards the nasal
side, is a small, round, apparently somewhat
depressed macular area of a dull-gray tone.
From its margins runs a double row of fine,
blue-green, translucent lines which form
about it a broken or irregular reflex ring.
The bird becomes unusually restless when
the light from the ophthalmoscopic mirror
is focused on this part of the fundus.

Glimpses of portions of the optic disc
show it to be dead white, and it seems to
have a fringe of short fibres of the same color
all about its edges. At the junction of
the pecten with the nerve-head, i.e., along
the central area of the latter, one sees numer-
ous brown pigment dots that appear like
small rootlets or capillaries and give a reticu-
late appearance to the papilla.

The pecten itself has a dark chocolate-
brown color and a corkscrew contour; it is
unusually long and narrow, and its lower
segment appears to come well forward
towards the lens.

Victoria Crowned Pigeon. Goura
victoria. The fundus oculi of this species,
depicted as Plate XI, page 131, right eye,
erect image, is of the usual gray color seen in
Pigeons and Doves. The eyeground gen-
erally is covered with minute white dots.
On the upper and nasal side of the fundus
is the macula, a small dull-gray area sur-
rounded by a gray and green reflex of small
lines.

The optic disc is long, narrow, boat-shaped
and a little rounded at the upper end. It
looks as it were rather hollow and gray in
the centre, with a white rim all around.
A network of small, brown, pigment dots
is disposed along the centre on either side
of the pecten; and some opaque nerve fibres
extend across the fundus on all sides of
the nerve.

The pecten is of the usual dark, chocolate
tint. It is corkscrew-like in appearance,
but one end is rather club-shaped and looks
as if it were covered with small brown nodules.
This segment comes well forward towards

the lens, but not so much as in the Wood
Pigeon; otherwise the fundus closely re-
sembles the eyeground of that bird.

Ralliformes

American Coot. Fulica americana.
(Figs. 120 and 84.) The background of this
species, macroscopically considered, shows,
obliquely across the fundus but not reaching
the periphery at either end, a "split stick"
figure — a narrow band of unpigmented retina
depicted by two dotted lines of pigment,
the line towards the optic disc containing
more granules than the other. Midway
between the two ends of this figure is a
circle of pigment, twice the width of the band
itself, made by an extension of the pigmented
borders that form the boundaries of the
band. In the exact center of the circle is a
plainly marked pigment dot.

The large, thick pecten is wider at its middle
than at either end. It has about 32 clearly
defined convolutions, or 16 double folds.
When seen from above one may perceive
between these plications not only the black
central body of the pecten but the papillary
edges. The free border of the pecten has no
definite keel but the upper margins of the
convolutions join to form a serrated wavy
line reaching from one terminal to the
other. This practically naked, saw-like
crest is unusual in the pectens the writer
has examined.

The long axis of the papilla prolonged
to meet the retinal band makes with it an
angle of about 70°, the infulapapillary angle.

Crested Coot. Fulica cristata. In the
several specimens examined ophthalmo-
scopically, the fundus appearances of this
Australian bird (see Plate XII, page 131)
were practically identical. The colored re-
production presents the left background by
the usual direct method.

The predominant color of the eyeground
is dull gray, everywhere sprinkled with mi-
nute, white dots that are more clearly seen
above the superior termination of the optic
nerve and to the nasal side of the pecten.
Although this area is (judging from the
effect of the light thrown upon various

THE FUNDUS OCULI OF BIRDS

Fig. 120. American Coot (Fulica americana) Xll.

Fig. 121. Great Crested Grebe (Podicipes cristatus) Xl2.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

quadrants of the fundus by the mirror) very
sensitive to light there is no other ophthal-
moscopic indication of a macular region.

The long optic disc is white, with a few
tiny pigment dots about its margins. The
pecten is lighter brown than in the majority
of birds; it is very large, almost hiding
the disc from view. Many opaque nerve
fibres radiate from the papillary circum-
ference and extend several disc breadths
across the fundus. Owing to the large size
of the pecten and the small pupil it is im-
possible to obtain a satisfactory lateral view
of the pecten, which almost covers the pupil-
lary area with its massive club-shaped end.

The American congener of this bird —
Fulica americana — has a fundus almost identi-
cal, ophthalmoscopically,with this species.

Ipecaha Rail. Aramides ipecaha. The
ophthalmoscopic picture of this bird, rep-
resenting the right eye, is seen as Plate XIII,
page 133.

The eyeground is a very pale uniform gray
stippled with darker gray and white dots,
thus giving the whole field a granular ap-
pearance.

The horizontally oval macular area (on
the nasal aspect near the upper end of the
disc) assumes a pinkish tone. At its center
is a small pit which, in the light of the mirror,
appears as dark gray with a brilliant, white
central dot. Around the macular region is
a pale, blue-gray reflex, which loses itself in
the general tone of the fundus but appears
quite sharp on the inner side of the oval
macular region.

The disc is a narrow, white oval, whose
major axis measures about one-third the
height of the pecten. A number of opaque
nerve fibres run across the background at
right angles to the papilla and fade into the
general gray of the fundus.

The pecten arises from the upper segment
of the disc, spreads out on it like the root of
a tree and gradually disappears into the
papillary substance. From this root a long,
slender, spiral form projects into the vitreous.
It is brown in color, is of uniform width,
looks like a corkscrew and extends forwards
and outwards as far as the eye can see,

looking as if it were pressed against the lower
part of the lens. The anterior end of the
pecten is much darker in color than its pos-
terior half, which is quite flat.

The fundus oculi of the Weka Rails (Ocy-
dromus) is quite similar to the ocular back-
ground of this specimen.

Podicipediformes

Great Crested Grebe. Podicipes
cristatus. (Figs. 121 and 83.) A macro-
scopic examination of the fundus oculi in
this species reveals a broad retinal band, uni-
form in width, that extends from the nasal
periphery across the fundus and is lost in the
pigment of the opposite side. It is half as
wide as the minor axis of the oval disc and,
along its whole length, is depicted by two
parallel lines of pigment dots — the inferior
border containing the more numerous grains.
The nasal half of the wide band is bisected
by a narrower, almost linear, ribbon com-
posed of minute black dots that are most
numerous at the periphery of the field,
becoming fainter and fainter until just
before the macula is reached, when they
disappear altogether.

At about a long papillary diameter from
the superior end of the pecten and on its
nasal side, is a large, circular, partly pig-
mented, disc-like macular region arranged
within and somewhat exceeding the limits
of the retinal band. It has, in its turn, a
central, depressed lighter area, surrounded
by a small ring of pigment.

The pecten covers the optic entrance, and
has the steam radiator-like form of the
Wonga Dove. However, this species ex-
hibits 24 convolutions, the free border shows
three definite elevations above and it has a
deep, opaque keel to which all 12 double
folds are firmly united.

The angle made by projecting the major
axis of the oval optic papilla until it bisects
the lower border of the retinal band, the
infulapapillary angle, is, approximately, 70°.

In injected specimens of this species (as
well as occasionally in individuals not so
treated) the choroidal vessels show very
plainly.

THE FUNDUS OCULI OF BIRDS

Fig. 122. Dark-bodied Shearwater (Puffinus grisetis) X9.

Fig. 123. Pigeon Guillemot (Cepphus columba) X9.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

Colymbiformes
Pacific Loon. Gavia pacifica. The
writer has never been able to examine more
than one individual of this species, or any
other Diver. He was obliged to use the
ophthalmoscope, with little protection from
the blazing sun of a Californian noon-day,
upon a recently dead bird. The examination
was necessarily incomplete. The fundus was
light gray, dotted over with dark pigment
granules; the pecten was large and there
was a well-marked porus opticus.

Sphenisciformes

Black-footed (Cape) Penguin. Sphen-
iscus demersus. The eyeground of this
species is depicted as Plate XIV, on page 133
of this monograph.

The dominant color of the fundus is bright
red shading to crimson. It is generally
stippled with minute, dark-red and orange
dots, much like grains of sand. About a
disc-length from the upper end of the optic
disc these dots become grayish-white; indeed,
the fundal coloration is distinctly gray
towards the upper half of the eyeground.
In a region the same distance towards the
temporal aspect of the background may be
seen a cluster of pinpoint, brilliant, white
dots in the macular area. Penguins use the
nictating membrane very frequently when
light is thrown on this part of the eyeground.

The optic disc exhibits enamel-white edges;
it is hollowed out in the centre, like a sewing-
machine shuttle. Running across this con-
cavity and at right angles to the margin of the
disc one sees a large number of gray fibres.

The pecten lies along the centre of the
nerve, where it is orange-red in color and
mottled with minute, brown pigment dots.
The pecten has the usual dark chocolate-
brown shade. It is of spiral form, like a cork-
screw laid on its side. A few slender opaque
nerve fibres are visible on each side of and at
right angles to the disc.

Procellariiformes

Dark-bodied Shearwater. Puffinus
griseus. (Figs. 122 and 85.) The fundus of
this species, as seen by the naked eye,

exhibits a darkly outlined band, widest at
the nasal extremity and at its middle, with
irregularly pigmented borders and a lighter
center, runs across the field of view from
one periphery to the other. Its central
third is shown as uncolored except for a
line of pigment that divides it into two equal
strips — thus constituting a linear fovea, the
circlet seen in some other band-like areas
being absent.

There are 20 convolutions in the rather
short, thick pecten. These double coils are
so divided where they join the compara-
tively narrow sloping crest that glimpses
may be had of the nerve head below. The
keel covering the upper portion of free border
is prolonged into a blunt, rounded process,
partly formed by the larger and higher
posterior "teeth" or segments of the mar-
supium.

What has by the writer been termed the in-
fulapapillary angle is 55°. This is made by
projecting the major axis of the papilla to meet
the lower margin of the transverse sensitive
area of acute vision.

Alciformes

Pigeon Guillemot. Cepphus columba.
(Figs. 23 and 82.) The background of this
species, when viewed macroscopically, re-
veals a narrow, uniform, pigmented retinal
band that stretches across the field of view
from one periphery to the other. At a point
where it approaches the superior end of the
papilla is placed a circular area (the fovea)
whose diameter is twice the width of the
band.

The pecten is remarkable in that it rarely
obscures a view of the margins of the long,
broad, ovoid, optic nerve-head, which has its
pointed extremity upwards. There are 30
convolutions in the pectinate mass, and
occasional views can be had of the papilla
through clefts in it. The ridge-like, free
border of the pecten is linear for a third
of its length below but follows the undula-
tions of the convulutions beneath it until
it reaches its superior end. The double
folds in this organ are longest and most
voluminous at their middle, where the

THE FUNDUS OCULI OF BIRDS

Fig. 124. Herring Gull (Larus argentatus) X7.5.

Fig. 125. Hudsonian Curlew (Numenius kudsonwus).
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

crest or keel is elevated to a sharp point,
and towards which the other folds are in-
clined. They gradually decrease in size
towards both the posterior free margin —
an unusual disposition — and to the anterior
or superior terminal of the optic entrance,
in accordance with the rule.

The longer axis of the disc projected until
it meets the retinal band makes with the
latter an infulapapillary angle of about 65°.

Puffin. Fratereula arctica. The eye-
ground of this remarkable species is portrayed
as Plate XV, page 135. It represents the
left eye as seen by the direct ophthalmo-
scopic method.

The general color of the eyeground is red,
rather uniformly stippled with small, mixed,
light-red and dark-gray dots. Above the
upper end of the optic disc and towards the
temporal side is a small, round, red area sur-
rounded by a pale, light-gray film, shot with
bright lines on the outer and inner margins —
doubtless the macular region with its central
fovea. Head noticed that not only this area
but most of the upper half of the fundus is
very sensitive to light.

The optic papilla, oblong, narrow and with
a rounded upper extremity, lies low down in
the eyeground, while the pecten extends well
forward and behind the lower margin of the
pupil. A view of the nerve-head is much
obscured by the body of the massive pecten
which almost covers it when seen, as with the
mirror, from above downward. The small
segment visible with the ophthalmoscope
appears not brilliant white but rather a bluish-
white, the margins of the pecten being covered
with black pigment.

Extending at right angles to the disc on
both sides are a few very fine, gray opaque
nerve fibres, that finally disappear in the
fundal periphery. The pecten is of the usual
chocolate-brown color and comes well for-
ward towards the lens, especially in its infe-
rior aspect.

Lariformes

Herring Gull. Lotus argentatus. (Figs.
124 and 86; macroscopic view.) In this
species the upper and more pointed extremity
of the pecten points slightly to the temporal

side of a linear fovea that is drawn as a rather
broad, short, retinal band that skirts the clear
area and stretches in a slightly oblique direc-
tion across about one-third of the central
field. The foveal slit (nearly as long as the
optic disc is wide) occupies a widened portion
of the band-like process and shows a line of
pigment dots along its upper margin.

The very broad, long pecten covers an
equally large papilla. It has 36 thin, leaf -like
convolutions which, in prepared specimens,
do not obscure the margins of the nerve-head,
whose canoe-shaped outlines are everywhere
visible from above, except at the bow and
stern. The free border, comparatively wide,
is deeply pigmented, does not reach the supe-
rior extremity of the pecten and has the
appearance of an ear of maize. The medial
and posterior leaflets of the pecten are the
longest, only the anterior five becoming
smaller as they approach the upper extremity
of the papilla.

The inf ulapapillary angle measures about 60?

The ophthalmoscopic appearances of the
background are the same in both the European
and New World species. A large number of
healthy individuals were examined both by
Mr. Head and the writer.

The ocular background of this bird is quite
similar to that of Larus marinus. The
prevailing color is dull brown, the upper half
being interspersed with masses of small gray
dots, that assume a pink hue downwards
from the upper end of the optic disc. One
notices in this region, also, many dull-red,
choroidal capillaries that run parallel to the
sides of the elongated nerve-head.

A little above the upper end of the papilla,
towards its inner or nasal side, is the fovea
centralis, a brownish red dot, in the centre of
a rather dull area. This macular region is
enclosed by two clear, bright green rings, or
reflex circles.

The optic disc (papilla) appears to be made
up of very short, brilliant white and rather
coarse opaque nerve fibres. Extending from
its margins are a few, dull-gray, opaque nerve
fibres, that radiate from the elongated papilla
but fade away in the periphery of the back-
ground.

THE FUNDUS OCULI OF BIRDS

Fig. 126. Black-bellied Plover (Squatarola squatarola) X9.

Fig. 127. Great Bustard (Otis tarda) X5^.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

The pecten, of the usual chocolate-brown
color, is divided into (about) fourteen con-
volutions, which are more massive below.
They extend well forward towards the lens.

At the apparent junction of the pecten with
the optic nerve the disc is rather orange-red
in tone.

Great Black-backed Gull. Lams mari-
nus. Plate XVI, page 135, depicts the fundus
appearances of the left eye in this species.
The general coloration of the eyeground
varies from a dull gray to a dull brown —
mostly the latter — traversing which are
many reddish, choroidal bloodvessels running
more or less in a vertical direction. It is the
number and visibility of these capillaries that
give the red tone to an eyeground essentially
gray.

The optic disc is a long, narrow oval, quite
white, with a quantity of fine gray lines radi-
ating in all directions from the papillary mar-
gin. On the inner aspect of the eyeground
the macula is seen. It is situated about one
disc-length from the upper end of the pecten
and half a disc-length above the end of the
same organ on the inner side.

The macula resembles a blue-green flake of
iridescent glass. It is of oval shape with a
reddish-brown center, which, however, is
unprovided with a reflex ring.

The pecten appears to be in folds; the lower,

or broader, portion extends well forward

towards the lens and turns towards the nasal

side of the bird's head. The inner quadrants

of the fundus are more easily seen with the

ophthalmoscope than the outer half but, so

far as the latter area is visible, there is no sign

of a second macula on the outer part of the

eyeground.

Charadriiformes

Black-bellied Plover. Squatarola squa-
tarola. (Figs. 126 and 89; macroscopic
view.) Preserved eyes of this species present
a moderately broad, grayish retinal band,
whose borders, drawn as pigmented through-
out, extend somewhat obliquely across the
fundus from one margin to the other. Near
the middle point of this retinal area is a cir-
cular, crateriform disc so set in the ribbon-
like figure that its circumference is not pig-

mented within the band proper but is con-
tinuous with the tinted borders themselves.
In some individuals there are traces of a
groove in the retinal band.

The pecten in shape resembles that of the
Hudsonian Curlew. It has 24 sausage-like
convolutions; its fringed keel being prolonged
at the inferior extremity into a spinous process
that (not shown in the cuts) follows the con-
cavity of the eyeball and almost reaches the
margin of the lens. One-third of the coils
present a concave surface to the posterior free
margin.

The infulapapillary angle is about 50°.

In prepared specimens the eyeball is ovoid,
with axes 8:9. In some individuals, also,
there are traces of a groove in the retinal band.

Hudsonian Curlew. Numenius hudsoni-
cus. (Figs. 125 and 88; macroscopic view.)
The background of this bird's eye shows a
broad, grayish band, with evenly dotted bor-
ders, that extends almost horizontally across
three-fourths of the visible fundus. It is
equally divided throughout its whole length
into two parts by a plainly marked line.

The major axis of the papilla projected
towards the band describes with the latter an
angle of 50°. It bisects it half the axial length
from the crater-like fovea.

The pecten, carrot-shaped from above, has
a fringed cap covering its upper free border.
It exhibits 34 convolutions, the spaces be-
tween the middle ten being deep enough to
allow a glimpse of the optic margins, that
are elsewhere completely covered. The
black, free margin corresponds in shape to the
pectinate body, being quite broad below,
narrow and pointed above. Its inferior third
is prolonged (into the vitreous) in the shape of
two conical elevations and a long, single
notched spine. The crest gradually slopes
from behind forward so that the posterior-
coils are the longest. Two-thirds of the coils
"face" forward.

Greater Yellow-legs. Totanus melano-
leucus. (Figs. 114 and 87; macroscopic
view.) In this species a broad retinal band,
faintly depicted with pigment fines, extends
across the entire visible field, its nasal half
being divided by a double-dotted line that

THE FUNDUS OCULI OF BIRDS

ends at the pigmented circumference of the
circular macula.

The macular region, twice as wide as the
surrounding band, presents a large, central
fovea.

The pecten has much the same shape as in
Squatarola; it is, however, a little larger, and
has 32 convolutions. The medium sized
coils, longer (taller) as one approaches the
posterior free margin, are capped by a deep,
irregular, partially serrated, ridge-like crest
that terminates posteriorly in a sharp point;
anteriorly the crest becomes much narrower,
and ends in a tapering triangle.

The optic entrance is (at its middle) seen
through the interrupted coils of the pecten;
and the infulapapillary angle, made by its
projected major axis and the lower margin of
the retinal band is between 45° and 50°.

The shape of this eyeball is oval, 10x11.

Stone Plover. (Edicnemus scolopax.
The fundus appearances (left eye, erect im-
age) of this nocturnal bird are depicted in
Plate XVII, page 137.

The eyeground is a warm brown or choco-
late color, rather deeply pigmented near the
periphery and covered with orange-red dots
that are very densely packed on the upper
half of the fundus. Below the optic entrance
are numerous choroidal vessels running paral-
lel with and on either side of the papilla.

The macula is difficult to distinguish and is
not clearly defined with the ophthalmoscope.
It is situated above the superior end of the
disc on its inner or nasal side, and about half
the apparent length of the pecten from the
upper end.

The papilla is white, oval in shape, fringed
all round with dense black pigment, and a
few gray, opaque nerve fibres are seen on
either side of it.

The pecten is very large and projects well
into the vitreous. It is of unusual shape,
rather narrow, but when examined from above

looks as if it had been compressed and flat-
tened on both sides, with a narrow edge above.

Great Bustard. Otis tarda. (Figs. 127
and 90.) The macroscopic reproduction of
this background shows a narrow fine of pig-
ment, representing the usual retinal band,
which extends horizontally across the central
two-thirds of the visible fundus. At almost
its exact middle is an incompletely oval area
encircled by a ring of pigment grains. A dark
spot (fovea) more or less surrounded by
black dots, occupies the centre of this crater-
like space.

The large and compact pecten forms a very
regular, oval figure whose extremities appear
to be of practically the same shape and size.
It is made up of about 22 convolutions united
in a crest that, from above, takes on the ap-
pearance of a fisherman's (cork) floater. The
pecten in this species is remarkable because
of the small number and large size of its folds,
because the central five of these are the long-
est, and because the middle half of the keel,
or crest, is projected as a tall cone into the
vitreous.

The major axis of this optic disc subtends

an infulapapillary angle of 70° with the linear

retinal band.

Gruiformes

Kagu. Rhinochetus jubatus. In many re-
spects the eyeground of this bird, as seen by
the ophthalmoscope, presents appearances
(see Plate XVIII, page 137) similar to the
fundus pictures (Plate XVII, page 137) of the
Australian Stone Plover, except that the
former has a gray area above the disc, instead
of a red and brown one. The drawing is of
the right eye, as seen by the erect image.

The background is, in general, covered with
a mass of minute dots that are gray in the
upper half of the fundus and orange below.
The lower sectors of the fundus are stippled
with pigment. Choroidal vessels are numer-
ous and run in rather straight, vertical lines
on both sides of the optic disc. They are
dull-orange in color.

The fovea is shown towards the anterior or
nasal half of the retina, and appears as a
round hole or crater-like depression, brown in
color, which reflects a grayish sheen from its

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

center. A narrow gray circle or reflex ring
surrounds this pit.

The optic disc has its central portion appar-
ently stippled with bright orange-red dots,
while its margin is fringed with coarse, white
fibres, that are also studded with brown pig-
ment dots especially near the outer border.

The pecten is of the usual deep, chocolate-
brown color, rather narrow where it joins the
disc but becoming much thicker and more
massive as it projects into the vitreous towards
the lens.

Brazilian Seriema. Cariama cristata.
This species presents an ophthalmoscopic
picture of the right eye, erect image, that is
reproduced as Plate XIX, page 139. The
dominant color of the fundus oculi is a dull-
drab. Over the lower quadrants of the
eyeground run rather straight, dull-red, cho-
roidal capillaries that fade away as they
reach the upper half of the field. This region
is also shot with a greenish-blue muslin-like
film, which is probably a reflection by the
retina of light rays from the ophthalmoscopic
mirror. Above the end of the disc is a small,
round depression, quite clear of any reflex.
To the inner or beak side of the eye is the
circular macula, whose diameter is about
three times that of the cavity at the end of the
disc. The center of the larger circle is quite
clear, with the exception of a bright shimmer, .
such as is sometimes seen about the human
fovea. The circumference of this circle is
very sharply defined, and has a bright ring
around it of glistening white.

The optic disc appears as a long, white
oval, with irregular margins.

The black-brown, corrugated pecten is very
large and long; it extends into the vitreous
and almost touches the lens with its club-
shaped terminal. Very fine opaque nerve
fibres radiate at regular intervals from the
whole papillary circumference.

In two eyes of this bird examined by the
writer there were, in addition to the appear-
ances just detailed, several scattered, red-
dish-brown deposits, very slightly pigmented,
in the choroid. These were found in an
individual captive in the Bronx Park for four
or five years, and were probably pathological.

Ardeiformes

American Black-crowned Night Heron.
Nycticorax nycticorax nosvius. (Figs. 92
and 129; macroscopic view.)

There were no definite, naked-eye indica-
tions of a fovea in the individuals examined.

The pecten, more pointed at its superior
extremity, exhibits 20 convolutions, so sepa-
rated that a view of the disc borders is here
and there obtained. The pectinate coils are
united by a narrow, cord-like crest that ex-
tends on the same plane and in a straight line
(except that at its middle point it is slightly
higher) along the upper free border from one
extremity to the other. The coils do not
differ much in length.

European Night Heron. Nycticorax
nycticorax. Seen with the ophthalmoscope
the eyeground (see Plate XX, page 139) is
dull gray, covered with grayish- white dots.
The lower part of the fundus exhibits a num-
ber of faint, reddish choroidal bloodvessels,
that run in a vertical direction, and whose
disposition is similar to the capillaries seen
in the fundus of the Boatbill, depicted in
Plate XXII, page 141.

The optic disc is long, but of medium width,
with both extremities rounded. Its center
is orange-red and covered with minute, brown
pigment dots.

The pecten is deep brown and its outlines
are well defined the whole length of the
papilla. Very thin grayish radiations extend
from the upper two-thirds of the optic
entrance.

The macula is situated quite close to (and
towards the upper nasal aspect of) the disc.
It is surrounded by an outer ring of whitish
lines; then, towards its centre is a zone re-
sembling the surrounding, punctated retina.
In its exact centre is a small fovea composed
of gray -white striae.

Great White Heron. Ardea occidentalis.
The individual examined by the writer had
been in captivity at the Bronx Park for sev-
eral years and was slightly myopic. The eye-
grounds of both eyes appeared identical and
the ocular organs were normal. The pupil
contracts under the strong light of the oph-
thalmoscopic mirror to medium size.

THE FUNDUS OCULI OF BIRDS

Fig. 128. American Bittern (Botaurus lentiginosus) X8.

Fig. 129. Black-crowned Night Heron {Nycticorax nycticorax ncevius) X6.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

The dominant color of the background is
light-reddish or brownish-gray and has appar-
ently a granular surface.

The papilla is white, almost entirely cov-
ered by the pecten and seems shorter than in
most birds.

The pecten is unusually large; only its free
end, which is blunt and rounded, can be out-
lined with the mirror. There is no well-
defined macular region.

American Egret. Herodias egretta. A
young adult was examined by the writer
in the Bronx Park. The dominant color of
the fundus in this species is a clear, bright,
steel-gray.

The pecten, an oblong with rounded ends,
covers most of the optic disc, whose white
border can be seen only on the outer side.
Striae, composed of whitish opaque nerve
fibres, radiate from the circumference at
regular distances from each other.

American Bittern. Botaurus lentigino-
sus. (Figs. 128 and 91.) This fundus when
seen by the naked eye and in prepared speci-
mens, shows two macular regions with their
fovea. The fovea nasalis — a large dot sur-
rounded by a nebular ring — just above and
slightly to the nasal side of the superior
extremity of the pecten. Temple-wards and
almost at the periphery of the visible back-
ground is the fovea temporalis — a less dis-
tinct area, also depicted as a central spot sur-
rounded by a ring of pigment grains. Allow-
ing for the concavity of the eyeball the two
maculae seem separated (in the figure) by
about two-thirds the length of the optic disc.

The coralliform, fenestrated structure of
the pecten is made up of 28 narrow convolu-
tions that are separated at their upper free
margins so as to allow, here and there, a good
view of the pigment-dotted surface of the
opticus. There are three (unequally) short and
eleven (equally) long double coils joined
above by a narrow but uniform crest.

European Bittern. Botaurus stellaris.
The left fundus oculi of this species is depicted
in Plate XXI, page 141 of this work.

The eyeground, mostly mouse-colored
shading to yellow, is sprinkled with small,
dull-white dots.

Almost immediately above the upper end
of the optic nerve entrance and towards the
nasal side of the disc is the macular area. The
fundal dots at this point are much duller in
tone and incline towards a dull, buff color.
The region of the macula, enclosed by two
circles, one within the other, is also char-
acterized by the presence of very short,
bright, bluish-green lines radiating from the
center of the fovea. These striations are very
brilliant and are easily seen by the aid of the
ophthalmoscope.

The optic disc is ovoid, blunt at its upper
extremity, and appears as if its longer mar-
gins describe a series of small curves corre-
sponding to the folds of the pecten. The
disc on either side of the root of the pecten
is dull-brown; near by are small, orange-red
choroidal capillaries. The papillary margins
are quite white and, in contrast with the
shadow cast upon the neighboring field by the
dark pecten, the disc stands out in sharp con-
tour. Extending a short distance over the
fundi and about the optic disc are a few
opaque nerve fibres. The pecten, con-
voluted, with serrated margins, and of the
usual chocolate-brown color, extends below
the lower end of the optic disc, and is plainly
visible. It does not project far into the
cavity of the vitreous.

Boat-billed Night Heron. Cancroma
cochlearia. The eyeground of this Central
American species is represented by Plate XXII,
page 141, and depicts the left eye by the erect
image. The prevailing coloration of the back-
ground is dull-red, covered with orange-red
dots. These punctate deposits are inter-
mixed on the upper half of the fundus with
smaller and brighter dots of a grayer tone.
On the lower half and on each side of the optic
nerve are a few orange-red choroidal capil-
lary vessels, that run in a vertical direction,
parallel to the long axis of the disc.

The macula is situated towards the nasal
side of the nerve head. This sensitive area is
rather brighter in color than the surrounding
field, and several white dots are included in it.
These small dots, however, are noticeable
only when the light of the mirror is reflected
on the region in certain directions. Rather

THE FUNDUS OCULI OF BIRDS

a bright, irregular and linear reflex surrounds
the macular region, which is very sensitive to
light.

There is a long, narrow papilla with rounded
extremities. It appears as if it were com-
posed of short, white fibres, surrounding an
orange-red center covered with minute, dark-
brown pigment grains that form a network
over the whole red area. Extending from
each side of the disc across the retina are a
few dull-gray, opaque nerve fibres.

The pecten can be traced the whole length
of the disc; it is dark brown in color and
grooved spirally like a corkscrew. It does
not appear to come far forward towards the
lens, and its union with the nervehead can
readily be traced. The pecten and its im-
mediate relations remind one of the fundus
oculi of the Bitterns.

Glossy Ibis. Plegadis falcinellus. As
will be seen on examining Plate XXIII, page
143, representing the left fundus oculi of this
species, the general coloration is blue-gray,
the eyeground being covered with a nebula of
minute, pale-gray dots, giving it a brilliant
gray tone when lighted up by the rays from
the ophthalmoscopic mirror.

Towards the lower part of the fundus and
on both sides of the optic disc, but parallel
with it, are many orange-red choroidal capil-
laries; they are especially numerous below
the optic nerve and suffuse the peripheral
background with an orange-pink glow.

Only one sensitive area is seen. This
macular region is located above the disc on the
nasal side of the nerve. In the center of the
area is a small, white, round dot, surrounded
by a brilliant blue-green reflex, like the sheen
on floss silk. It is probably due to the play
of light on the fine fibres radiating from the
center of the fovea.

The optic disc looks as if it were a mass
of coarse white fibres; it is similar in shape
to the papilla of the Spoonbill, but it can
be traced only for about half its length,
the lower part being obscured by the mas-
sive club-shaped pecten. The disc is bor-
dered with black pigment which gives the
appearance of a shadow cast on the eye-
ground. This organ is of the usual chocolate-

brown color and projects well forward towards
the lens.

A large number of semi-translucent nerve
fibers radiate from the margins of the optic
nerve on all sides; they extend across the
choroidal vessels, and finally vanish alto-
gether in the fundal periphery.

American Jabiru. Mycteria americana.

The fundus of the left eye is depicted in
Plate XXIV, page 143 by the direct method.
The general coloration is a slate-gray, the
whole eyeground being quite uniformly
sprinkled with small but variously sized,
white dots. In the upper and nasal quadrant
of the picture is the small, single macula, an
area darker than the surrounding parts, whose
exact centre shows a round white dot — the
fovea. In the lower two-thirds of the field
are seen numerous, plainly marked choroidal
vessels that extend the whole length of the
pecten, converging somewhat towards the
posterior aspect of its base. About two-
thirds of the long and rather broad nerve-head
is plainly visible, except the central portion,
which is partly obscured by the pecten. This
large, black-brown organ, divided into 15
large and several much smaller double folds,
terminates above as a thin, dark rod. The
disc is fringed by black pigment grains, and
from its lateral margins project a number of
short, faint, whitish lines.

Spoonbill. Platalea leucorodia. The col-
ored fundus view (see Plate XXV, page 145)
is of the erect image, left eye. In general
the color of the eyeground is decidedly gray,
becoming brownish towards the periphery.
It will be noted that the entire fundus is
thickly sprinkled with minute, irregularly
shaped, gray-white dots, that appear more
distinct about the macular region.

At the fovea, where they are brilliant
white, they are still more closely packed.
With the ophthalmoscope the foveal region
appears to be sunken below its surround-
ings, and to be enclosed in a pale, greenish
(reflex) ring that is of oval shape with its
long axis horizontal. Judging from the
effect on the bird when the direct light from
the mirror is thrown upon it, this area is
extremely sensitive to light.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

The optic nerve-entrance is a long, narrow
oval, and presents a brilliant white appear-
ance. Near its upper end are several choroi-
dal capillaries of a pale, golden-yellow color.
Parallel to the long axis of the nerve-head is
another elongated mass of white fibres *
(almost like a second optic disc) having its
center stippled with fine pigment dots, and
extending across the eyeground. Radiating
from the circumference of the papilla one
sees a number of faint, translucent fibres,
crossing the small white area on the nasal
side of the nerve.

The pecten does not project very far
forward into the vitreous; it is dark gray-
brown and appears to be completely covered
with a number of warty protuberances.
It appears to be attached to the whole length
of the centre of the disc, that is stippled
with fine, red dots.

Anseriformes

Black-bellied Tree Duck. Dendro-
cygna autumnalis. The fundus appearances,
as revealed by the ophthalmoscope in six
eyes of three individuals, are depicted as
Plate XXVI, page 145. Five normal eye-
grounds were identical; the sixth exhibited a
congenital defect of the nerve-head which
entirely changed the fundal picture.

The fundus oculi of the Tree Duck is colored
a light fawn, besprinkled with minute, white
dots, that glisten when a strong light from
the mirror is thrown upon them. On each
side of the papilla is seen a number of choroi-
dal capillaries, bright orange in color and
rather straight.

The optic disc is also orange-red along its
major axis, this central zone being stippled
all over with a network of fine black dots.
The circumference of the disc is fringed with
white fibres.

The dark-brown pecten arises, as usual,
from the whole length of the disc. Viewed
from above it seems very thin and twisted,

* Whether this is a normal condition or an anomaly
of development cannot be definitely stated without
an examination of additional specimens, but it was
present in both eyes of the individual under con-
sideration.

like a corkscrew. A few opaque nerve
fibres extend for a short distance and at
right angles to the disc on either side. The
upper part of the fundus is almost obscured
by numerous minute, brilliant, white dots.
Although Head noticed that when he focused
the bright light of the mirror on the upper
quadrants of the fundus the Ducks used
their membrana nictitans more frequently
than usual he could not discover any well-
defined sensitive area.

Blue-winged Teal. Querquedula dis-
cors. The general appearance of this bird's
eyeground closely approaches that of the
Mallard. The long, ovoid papilla is disposed
with its major axis at right angles to the
upper mandible.

Mandarin Duck. Aix galericulata. In
examining the eyeground of this species the
writer found that the light of the ophthal-
moscopic mirror, when projected on the
eyes directly from the front, illuminates,
roughly speaking, about one-sixth of each
field. '

The prevailing color of the background
is light, gray-brown, streaked with faintly
marked choroidal capillaries, that are,
however, confined to the nasal side of the
disc.

The direct method shows a vertically
placed optic entrance, that appears to stretch
almost over the whole fundus. The field on
the outer aspect of the disc seems to be
superficially roughened or granular. There
are no radiating opaque nerve-fibres or con-
centric reflex rings visible with the mirror.

The pecten is comparatively small, does not
entirely cover the disc and presents from
above downward a reticulated appearance.

Mallard Duck. Anas boscas. The
general coloration of the fundus of this bird is
gray-red. The optic nerve entrance is much
longer than in most species, extending in a
perpendicular fashion across the background;
it is in no place obscured or entirely hid by
the pecten. The papilla appears to be
attached for three-fourths of its course to
the latter, which arises in partially trans-
lucent, veil-like folds and extends to the
posterior surface of the lens. No concentric

THE FUNDUS OCULI OF BIRDS

circles of opaque nerve fibres are visible.
The whole background, including the disc,
seems to be dotted with many punctate
pigment grains.

Canada Goose. Branta canadensis. The
individuals of this species examined by the
writer had been domesticated in the Bronx
Park for several years but under conditions
approaching their usual habitat.

The appearances of the fundus oculi were
practically identical in all the specimens
examined, and are similar to those of the
Mallard. The concentric arrangement of
the optic fibres in Anas is lacking in the
Brant, while the latter has the larger pecten.

Although the pecten is rather large, the
outlines of the vertically oval, yellowish-
white papilla are visible throughout.

Blue (Snow) Goose. Chen c&rulescens.
Plate XXVII, page 147, reproduces the fund-
us appearances of two individuals examined by
Mr. Head and of another seen by the writer.
The backgrounds were the same in all.
The predominant fundal color is a distinct
fawn, sprinkled with small, round, orange-
pink dots of irregular shape and size. Run-
ning vertically past and parallel with the
optic papilla, over the lower half of the
fundus, are numerous, straight, orange-red,
choroidal capillaries.

The fovea is probably indicated by a small,
glistening white dot above the end of the disc
on the nasal side. This small, punctate
deposit nearly disappears when the light
from the mirror is turned in certain directions.
An inconstant, bright-green reflex is notice-
able in this part of the eye, and there is a
decided photophobia when the ophthal-
moscopic light is flashed upon the region
of the supposed macula. Moreover, by
careful focusing the circumference of the
foveal (?) dot shows a small brown rim, like
the sides of a crater. However, the light
from the mirror does not reveal any actual
depression; the eyeground appears level
throughout and is uniform both in color and
texture.

|The optic nerve-head is boat-shaped, tinted
orange along its central zone and shows a
narrow rim of coarse opaque nerve fibres

that form a fringe about its circumference.
This orange centre is sprinkled with numer-
ous minute, dark-brown or black dots. A
few gray opaque nerve fibres arise from the
disc margins, and cross the fundus horizon-
tally. The pecten, of corkscrew shape, runs
the whole length of the disc and comes
well into the vitreous.

Lesser Snow Goose. Chen hyperboreeus.
(Figs. 93 and 131.) There is, judging from a
naked-eye survey of this fundus, a grayish
but well-defined, rather narrow, retinal
band, devoid of pigment, that runs obliquely
through the center of the field from one
periphery to the other. It is more definitely
outlined by pigment grains on its inferior
than on its upper margin, especially where
it traverses the nasal half of its course.
About its middle point is the single macular
region and fovea — a short but regular line of
pigment in the center of an enlargement
of the band.

The large, shoe-shaped pecten is com-
posed of 24 heavy, compact convolutions
that terminate in a cigar-shaped superior
and a triangular inferior extremity. The
conical crest of the upper free border is
wide for three-fourths of its entire length.
It terminates in a thin, corkscrew process
before it reaches the tip of the upper con-
volution, which almost touches the retinal
band, with which the (projected) major
axis of the nerve-head describes a right
angle. The convolutions decrease pari passu
in size from behind forward, all the coils
inclining towards the lower end of the disc.

Pho enicopterif ormes

Common Old-world Flamingo. Phoe-
nicopterus roseus. (Figs. 94 and 115; macro-
scopic view.) This ocular background shows
a small but compact penten, whose 18
convolutions are (apparently) drawn towards
the center of the organ above by a deep,
cigar-shaped crest, so that the marsupium
resembles, when viewed laterally, a truncated
cone.

Stretching obliquely across the fundus is a
light-colored, retinal band of medium width,
which ends abruptly just before it reaches

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

Fig. 130. Brandt Cormorant (Phalacrocorax penicillatus) X9.

Fig. 131, Lesser Snow Goose (Chen hyperborea) X9.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS OCULI OF BIRDS

the temporal border of the field. Two lines
of pigment dots — the one at the nasal end
more plainly marked and each as long as
the disc — divide the terminals of the band
into two narrow spaces. The lower margin
of the band is drawn with numerous minute
pigment grains that are sparsely supplied
to the upper border except at its nasal end.
A third line of pigment, deeper in color than
the other two, and about as long as the
papilla is wide, indicates the middle point
of the band somewhat nearer its temporal
end. At this point the band becomes slight-
ly broader, especially below. In the centre
of this shortest line the pigmentation is
somewhat pronounced, but an outline of the
ordinary slit-like fovea within a retinal band
is not here well developed.

An extension of the long diameter of the
papilla to meet the lower border of the retinal
band, makes with it an infulapapillary angle

of 65°.

Pelecaniformes

Cormorant. Phalacrocorax carbo. The
fundus view shown in Plate XXVIII, page
147, of this work, represents the ophthalmo-
scopic examination of eight eyes of four indi-
viduals. Two were tame birds, the others
were freshly caught, but their eyegrounds were
identical. The drawing presents the appear-
ances in the left eye by the direct image.

The fundus oculi is mostly of a slate-
gray color, uniformly sprinkled with numer-
ous, minute white dots, closely packed
together. Running chiefly parallel with the
long axis of the optic disc are several rather
straight, orange-red choroidal capillaries,
that extend the whole length of the papilla
and beyond its inferior extremity.

The macular area is seen a little above the
upper end of the optic disc and on the nasal
side of the nerve. The fovea appears as a
reflex image of a few short, bright, white lines
surrounded by a narrow and similar ring.

The optic disc gives the impression that
it is composed of a mass of very white,
cotton-like fibres, disposed as a fringe all
about the papillary margin. The central
area of the disc, especially on each side of
the root of the pecten is orange-red,

stippled with minute, brown pigment
grains. Perpendicular to the papillary mar-
gins are a few short, fine opaque nerve
fibres, that run towards and are finally lost
in the peripheral eyeground.

The pecten is rather long and of the usual
chocolate-brown tint; it is much narrower
than usual on the upper half of the disc,
and comes well forward into the vitreous
humor, extending behind the margin of the
pupil.

Fallarone Cormorant. Phalacrocorax
dilophus albociliatus. An adult individual of
this species (while dying) was examined
by the writer in an open boat in San Diego
Bay, California. An ophthalmoscopic view
was obtained under these difficulties, and
is consequently incomplete. However, the
writer saw through dilated pupils that the
fundus was gray-black and uniformly dotted
throughout. The pecten was easily seen,
but not well enough to count or accurately
describe the arrangement of its plications.

Brandt Cormorant. Phalacrocorax pe-
nicillatus. (Figs. 95 and 130.) This fundus
oculi, when viewed with the naked eye, in pre-
pared specimens, shows a broad, gray band
depicted in the black and white drawing as
extending in a rather oblique direction from
the nasal periphery of the field to a point im-
mediately above the superior end of the pa-
pilla. Here, just before it terminates, the
band widens and develops into an oval area
with a large central, black dot, crowned by
minute and scattered pigment grains. This
macular area is located about the width of the
minor axis of the optic disc from the upper ex-
tremity of the latter.

[In the temporal margin of the black-and-
white drawing is a slit-like mark; this is not a
second fovea but an artefact fold in the retina.]

The pecten presents a broad, and rather
long, pointed oval, with its blunt extremity
below. It is composed of 32 convolutions
whose free margins are united above in a keel,
and whose wide and thicker posterior fourth
covers nine equally long double coils. It
then slopes to the superior pointed extremity
of the disc, having joined, above, the remaining
nine unequally short coils.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

Gannet. Sula. bassana. The picture of
the fundus, as shown in Plate XXIX, page
149, is the result of ophthalmoscopic exami-
nations of three healthy, adult specimens. It
depicts the left eye ; erect image. The general
color of the eyeground is dull-yellow with
a gray tint, everywhere covered with light
gray dots, that are most numerous on the
upper half of the fundus. Below and on
each side of the optic nerve are several
orange-red choroidal capillaries. These ves-
sels are fairly straight and run parallel with
the long axis of the disc.

The nerve-entrance and pecten are situ-
ated rather high up in the field ; consequently
it is easy to examine the details of the peri-
papillary background.

Above the upper end of the optic disc
and a little towards the nasal side, is a small
circular macular area, red in tone but sur-
rounded by a larger circle, like a gray shadow.
The margins of the latter gradually fade
into the background.

The visible margins of the papilla, apparently
composed of coarse, white, opaque fibres,
are not, as in many species, covered by the
pecten. The central part, near the root of the
pecten, is orange-red in color.

The pecten itself is evidently attached to
the disc for nearly its entire length, and
does not appear to come forward towards
the lens.

Redback Pelican. Pelecanus rufescens.
The individual (male) examined by the
writer was five years old and had been
domesticated in the Bronx Park for at least
three years. His refraction, estimated by
the skiascope, was about +1.D. The general
coloration of the ocular background is a well-
diffused, light reddish-brown; in some parts
of the field verging on gray. The pecten is
very large — larger at its free than at its
papillary extremity — and twelve distinct
corrugations in it are visible and can be
counted by the aid of the ophthalmoscope.

Although the canoe-shaped optic papilla
is almost entirely obscured by the mass of
the pecten yet it is uncovered towards its
temporal end, where it presents a very
white, pointed extremity; elsewhere it ap-

pears reddish-brown. Radiating fibres sur-
round the disc, like a halo.

Australian Pelican. Pelecanus con-
spicillatus. The fundus appearances of this
bird, as demonstrated by the ophthalmo-
scope, are portrayed in Plate XXX, page 149.

The predominant color of the eyeground
is a dull but deep gray, sprinkled generally
with irregular dots, most numerous in the
upper part of the fundus. The lower quad-
rants of the field are covered with a dull,
orange-red, choroidal capillary system, dis-
posed in a vertical direction. The disc is
a wide, pointed oval, exhibiting a number of
bright-red orange ridges that are uniformly
stippled with black pigment dots. The
disc margins stand out as a clear white.

The pecten, broad and massive, seems to
fill the pupillary area. It projects far into
the vitreous, reaching, indeed, the posterior
surface of the lens. In spite of its large
size and intraocular disposition both the free
and the attached ends of the organ can be
outlined by the ophthalmoscope. Passing in
a radial direction from its circumference is
a number of opaque nerve fibres.

The single macular area is to be found on
the inner side of the fundus. It is surrounded
by a narrow, sharply defined, reflex ring of
greenish color.

California Brown Pelican. Pelecanus
calif ornicns. A young adult was examined
on the Coronado Islands, Mexico, by the
writer. The pupils measured about 5 mm.
and were not affected by light, as the bird
had just died. The fundus was well seen.
There was a distinctly whitish background,
almost uniformly covered with minute gray-
black dots. The pecten was large, and of
the corkscrew type, almost covering the
whitish-yellow optic disc whose margins were
easily made out. This bird seems, from the
position of his eyes and their frontal disposi-
tion, to have binocular vision.

Serpentariiformes

Secretary Bird. Gypogeranus (vel Ser-
pentarius) serpentarius. The ocular back-
ground of this species presents a most unusual
appearance. The colored drawing (Plate

THE FUNDUS OCULI OF BIRDS

XXXI, page 151), depicts the right fundus
by the erect image. The general color of the
eyeground is dull gray, pitted all over with
mixed light and dark brown pigment grains or
dots, the darker being about double the size of
the lighter granules. Interspersed with these
dots is a dense mass of minute, bright points
that cover the whole fundus, but they can be
observed only when the reflected light of the
mirror is focused upon them. These various
deposits give the background the appearance
of a rough surface. There are no visible
choroidal bloodvessels, but a thin layer of
translucent nerve fibers surrounds the papilla
for a short distance, particularly along the
long axis of the nerve-head.

A little above the upper end of the optic
disc and towards the nasal side is the fovea
centralis, a round white dot enclosed by a
narrow ring of bright green. This area is
extremely sensitive to the reflected light of the
mirror. On the temporal side of the disc,
and above the end of it, is also a long, narrow,
sensitive area. This part is enclosed by a
shimmering reflex of green fight. The animal,
otherwise quiet, becomes very fidgety when
this area of the fundus is examined, and gasps
for breath as if it was being suffocated.

The optic disc is long and rather narrow,
both ends being rounded off. It is quite white
and deeply pigmented at its outer and upper
borders.

The pecten is of a lighter brown than usual,
is plainly serrated on either side and appears
as a narrow band that extends the whole length
of the disc. Just before its junction with the
optic nerve-head it is stippled with bright,
orange-red grains. The central part of the pec-
ten does not project far forward into the vitre-
ous; it appears to be quite narrow, while the
whole length of its upper edge or crest seems
rather wavy. On the whole, the fundus ap-
pearances present a picture unlike those of any
other species examined by Head or the writer.

Accipitriformes

Lammergeier. Bearded Vulture. Gypae-
tus barbatus. Plate XXXII, page 151, repre-
sents an ophthalmoscopic view of the right
ocular fundus (erect image) of this bird.

The eyeground is slate gray, not stippled, as in
so many avian fundi, but presenting every-
where a granular appearance. The lower
half of the fundus is covered with dull, orange-
red choroidal bloodvessels that run in a ver-
tical direction, parallel to the sides of the optic
disc.

All the fundal sectors are clearly seen.

The optic entrance is pure white, with an
orange-red central area from which arises the
pecten. This body is very narrow and tapers
on its upper aspect for about one-fifth of its
length. It then becomes much broader and
almost covers the outer zone of the disk. As
it comes forward towards the lens its contour
resembles that of the Bald Eagle.

This fundus is singularly free from opaque
nerve fibres.

Bald Eagle. Haliaetus leucocephalus.
The fundus picture seen in Plate XXXIII,
page 153, is the result of an examination of a
number of individuals. The writer, for ex-
ample, had an ophthalmoscopic view of the
eyeground of five Bald Eagles in the Bronx
Park collection.

The prevailing color of this bird's fundus is
dark reddish-brown, the lower half changing to
a dull orange-red. The whole eyeground
is covered with choroidal capillaries, and
dotted over with brown pigment grains, giving
it a rough, granular appearance. A gray
sheen pervades the upper part of the fundus.

On the temporal side and some distance
from the upper end of the optic nerve is a
brilliant, white, round dot surrounded by a
small, light-green reflex ring, which is itself
enclosed in a very brilliant, narrow green
ring — the muscular region. On the nasal
side of the disc, and on a level with this

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

macula is another area, of a gray color, sur-
rounded by a fan-shaped, luminous reflex.

The optic nerve-entrance is distinctly white,
and along its center is strewn a large number
of minute pigment dots. The outer margin
of the disc is bordered with black pigment,
as if a shadow were cast upon it by the pecten.
In this regard and in some others this fundus
resembles the eyeground of the Sea Eagle.

White-bellied Sea Eagle. Haliaetus
leucogaster. The ocular fundi of three in-
dividuals of this species were found to be iden-
tical and furnish the ophthalmoscopic appear-
ances shown in Plate XXXIV, page 153.

The coloration of the eyeground is mostly
dull-brown, the lower quadrants of the field
being covered with dull, orange-red capil-
laries evidently choroidal.

The optic disc is a long white oval, whose
center is tinted with orange and covered with
tiny pigment dots. The papillary margins
are white bordered with black pigment.

The upper half of the fundus is covered
by a mass of dull gray dots. There is a well
defined reflex near both maculae, each similar
in position to that seen in the Kestrel. These
areas are evidently very sensitive to light, as
the bird becomes very fidgety and irritable
when the reflected rays from the mirror are
thrown directly on one or other fovea.

The pecten is very large and comes well
forward towards the posterior surface of the
lens. [Both extremities of the organ are
clearly visible through the ophthalmoscope.
There are very opaque nerve fibers to be seen
in any part of the eyeground.

American Osprey, or Fish Hawk. Pan-
dion haliaetus carolinensis. When light is
thrown directly from the front and at a dis-
tance of one foot, on the pupils of this bird of
remarkable visual powers the red reflex is
seen to occupy fully three-fourths of each
pupillary area.

By the aid of the ophthalmoscope the
writer found the general fundal coloration to be
bluish-gray with a suggestion of brown.
These tints are uniformly distributed through-
out the ocular background, and there is very
little of the striation seen in Buteo and other
genera.

The pecten almost entirely obscures the
view through the pupil of the optic disc; it
is a compact, intensely black body, showing
about ten convolutions.

Mainly because of the undilated pupil and
large pecten no definite fovea was visible.

European Kestrel. Tinnunculus alau-
darius. Plate XXXV, page 155, is a faithful
reproduction of the ophthalmoscopic appear-
ances in this sharp-sighted species, depicting
the right eye by the direct method.

The ground-color of the fundus is a light
brown, or brownish-gray. The lower quad-
rants are streaked with orange-red, choroidal
capillaries that run in a more or less vertical
direction, and become more distinct and
brighter red as they approach the periphery
of the field. The optic disc is a long, white
oval, showing its margins well beyond the
pigmented and fringed pecten. The central
area of the papilla appears to be hollowed out
like a canoe and the pecten does not overlap
it at any point of its circumference, as is so
frequently the case in avian fundi.

The disc extends as far downwards towards
the fundal periphery as the observer's eye can
reach. At its lower extremity several small
choroidal vessels can be seen.

The pecten has a rounded but pyramidal
form, sloping towards the centre of the disc
at both ends. It is of a dull-brown color, and
corrugated like a photographic camera. At
the junction of pecten and papilla are scat-
tered numerous brown dots, so disposed as
to give the former the appearance of a web.
The upper part of the eyeground is quite
devoid of choroidal blood-vessels, but is
covered with minute white dots. The fundus
is much clearer of the retinal shimmer or re-
flex noticed in most birds.

The two macular regions are very distinctly
visible. The nasal macula is situated just
above the upper end of the disc and about
half a disc-length on the inner or beak side
of the eyeground. It is a dark-brown spot
with a pale area all around it. Outside of this
region and enclosing it are two distinct, pale-
green, filiform, reflex rings, the interior rings
being quite free from the white dots. On
the outer aspect of the eyeground, about

THE FUNDUS OCULI OF BIRDS

one-third the length of the disc above and two-
thirds to its outer side, is seen the second or
temporal macular region. At its center is a
light, gray spot surrounded by a dark brown
area. Both these arese are in their turn
encircled by a small, pale-green, reflex ring
about one-fourth the diameter of the corre-
sponding circle about the superior macula.
Slender, opaque nerve fibers run out at right
angles to the disc on both sides.

Red-tailed Hawk. Buteo borealis. The
optic-nerve entrance in the individuals examined
by the writer is almost entirely covered by the
pecten, except at its superior end, which can be
outlined and examined by the mirror. It lies
(obliquely) at an angle of about 70 degrees with
the upper mandible, and can be seen through
the more or less translucent pecten. The back-
ground generally has a striated appearance
with the choroidal vessels showing through.

Little Bustard. Tetrax tetrax. Plate
XXXVI, page 155, reproduces the left fundus
oculi, direct image, of this species. The
fundal coloration is mostly a warm gray,
covered with small, dull orange-red dots. In
the lower half of the field and on each side
of the optic nerve entrance is a number of
choroidal blood-vessels of a dull orange-red
color, running parallel with the disc.

So far as seen, the papilla is a dead white ;
optic fibres form a fringe-like setting about it.
The central zone of the disc is covered by a
mass of minute, brown, pigment deposits of
irregular shape. Opaque nerve fibres extend
at right angles to the disc on either side.

A little to the temporal side, about one
disc-length from the upper end of the optic
nerve, is a small, brown spot like a tiny hole.
This macular area is surrounded by a brilliant,
green reflex ring.

The pecten, of a dark chocolate-brown color
and shaped like a corkscrew, comes well for-
ward towards the inferior border of the lens.

The fundus of the Great Bustard — Otis
tarda — closely resembles that of 0. tetrax.

Strigiformes

Tawny Owl. Syrnium aluco. (Figs. 132
and 96). The ocular background of this
species shows, macroscopically, a solitary,

temporal, macular region and fovea. This
single macular area is about a disc length and
a half above and to the temporal side of the
smaller or superior end of the pecten.

The irregular shape of the eyeball and fun-
dus in the Owl must not, in this connection,
be forgotten. The comparatively undersized
pecten exhibits 14 convolutions (four large
and of equal size, ten unequally smaller) that
when viewed from above look like a small
bunch of raisins. Between the folds may
be seen the margins of the optic nerve en-
trance. The crest surmounting the upper free
border is very thin, inconspicuous and unde-
veloped.

The ophthalmoscopic view of the normal
fundus (the result of examination of numer-
ous individuals) is shown in Plate XXXVII,
page 157.

On the outer aspect of the papilla and
about one disc-length from it, on a level with
the upper margin of pecten, is a slight de-
pression {macula) almost devoid of cho-
roidal vessels. Its centre is a dark red color,
the whole macular region closely resembling
the same area in the (brunette) human eye.
On the margins of this depression and sur-
rounding it is a bright circular reflex. Head
found this reflex to be so bright and dense in
some individuals that it was difficult to see
the other macular details, although, in most
instances, by shifting slightly the reflected
rays from the mirror the macular margins
come out distinct and sharp. For some dis-
tance outside this foveal ring the eyeground
is seen as if one were viewing it through a
translucent, grayish mist or haze; and the
fundus thus seen generally appears to be
granular with a few, small choroidal capillaries
showing here and there. Inside the ring,
however, the details are strikingly clear, and
the coloration bright red. Above the macula,
on the outer side of the disc, is a quantity of
dark pigment deposited between the cho-
roidal vessels, by contrast making the latter
stand out as of a bright orange color. The
inner aspect of the fundus appears yellow; it
exhibits numerous choroidal blood-vessels,
whose yellow tint is distinctly brighter near
the inferior segment of the disc.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 93

Fig. 132. Tawny Owl (Syrnium aluco) X7.

Fig. 133. Greater Sulphur-crested Cockatoo {Cacalua galerita) X9.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS OCULI OF BIRDS

Burrowing Owl. Spcotyto cunicularia
hypogoea. The ocular fundus of this species is
irregularly round, as in all the Owls, and
in prepared specimens the details show dis-
tinctly.

The single, temporal, oval macular region
lies above and about a disc length and a half
from the upper end of the papilla. In the
center of the macula is the fovea — a dark
pigmented spot with fine granules arranged
cap-like above it. Outside this, again, is the
ovoid circumference of this region, incom-
pletely edged with fine dots. These are more
numerously distributed below the macula
than above it. Connected with the macular
region is a light colored and rather broad band
that extends horizontally to the center of the
visible background. It is unevenly divided
into two strips by a parallel arrangement of
minute pigment dots.

Seen from above the relatively small pecten
closely resembles a disarticulated, acuminate
leaf, the stem representing the spinous pro-
jection immediately above the lowest terminal
convolution. The light double folds of the
marsupium slope backwards and cover most
of the optic entrance; they meet above in a
uniform, very narrow, slightly undulating
crest whose posterior end projects half the
height of the unlying coil well into the vitre-
ous cavity. An extension upwards of the
long axis of the disc cuts the retinal band at
the junction of the inner and second fourth,
making an infulapapillary angle of, perhaps,
40°.

This interesting Owl is especially subject,
like other Strigiformes, to pathological varia-
tions in the fundus picture due to confinement
and domestication. Both Head and the
writer examined a number of individuals that
undoubtedly exhibited choroidal disease and
other pathological changes. Rejecting these,
the general color of the fundus of this species is
found to be dull-orange, mottled and blotched
in its upper half with orange-red. Choroidal
vessels are plainly seen, covering all the lower
part of the eyeground, just as in the Tawny
Owls. The well defined macular area is seen
within the outer half of the fundus, a little
above the upper extremity of the optic disc.

It is distinguished from the surrounding cho-
roid by a collection of minute pigment
granules or dots with a bright, white spot in
their centre.

The optic disc is white and of oblong shape,
slightly rounded at the ends. From its edges
run a few, short nerve fibres that form a com-
plete fringe about the visible papilla.

The pecten is decidedly larger in proportion
to bodily measurements than one finds it in
most of the larger Owls, especially larger than
in the Tawny Owl. It extends well forward
into the vitreous, and its lower half appears
very massive and of a dark brown color. The
pectinate convolutions are plainly seen and
the anterior or upper half is more delicate in
structure, being perforated where it joins the
disc. Here it forms a dark network on the
surface of the nerve-head where, also, a few
red granules mingle with the chocolate-brown
texture of the pecten.

Snowy Owl. Nyctea nyctea. It is a popu-
lar belief, and one held in many public
aviaries, that these owls are likely to become
blind if much exposed to daylight. Conse-
quently they are often caged in darkness or
semi-darkness, although their habits are really
diurnal, or at least they are as much Day
birds as Night birds.

In any event the changes in habitat in-
volved in their captive surroundings are, in
the judgment of the writer, responsible for
certain alterations found in their fundi and
in those of other Bubonidae kept for more
than a year or two in public gardens.

The normal, dominant coloration of the
fundus is very light yellow-red, but de-
cidedly less red than in Syrnium aluco. See
Plate XXXVII, page 157, of this Atlas. In
the first individual (two years in captivity)
examined there were throughout the left back-
ground extensive choroidal changes, especially
one cruciform, pigmented, partially atrophic
area running across the field towards the
nasal side. These long, striated alterations
were also seen in the temporal part of the
fundus.

The large, club-shaped pecten springs from
a well defined whitish, ovoid disc. The mar-
gin of the papilla is occupied by numerous

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

small, dotted, pigmented deposits. The ocular
media were entirely clear.

In the right fundus the pathological changes
were the same except that towards the nasal
side of the papilla there was a large, atrophic,
pigmented area extending almost to the
periphery of the fundus, entirely unlike the
smaller and narrower lesion in the left eye.
Altogether the morbid changes in the right
eye are more numerous than in the left.

In a younger individual the coloration of
the background, the papilla, the pecten and
the macular region were precisely as in the
first-mentioned bird. The pathological le-
sions, however, were entirely different. They
appeared in each eye as four or five rather
small, round, pigmented exudates, having a
whitish atrophic (?) centre, much like the
medium-sized deposits in the human eye
when affected by a disseminated choroiditis.

European Barn Owl. Strix flammea.
(Figs. 97 and 112; macroscopic view). This
fundus shows the single sensitive regions
{macula and fovea) on the temporal aspect of
the field, slightly above and less than the long
disc-diameter from the upper termination of
the optic entrance. The fovea is represented
by a large dot in the center of a number of
minute granules, surrounded by an untinted
area inclosed in a ring of still more numerous
pigment grains.

The small pecten is made up of 14 short,
stout convolutions (the largest ten of equal
size) that only partially cover the nerve head,
which has pigment granules scattered over
its surface. The pectinate coils meet above
and are joined by a straight, thin, cord-like
crest. They all incline towards the posterior
free border. The upper free margin is about
half the length of the papilla.

The fundus oculi of the British species,
painted from a recently captured specimen,
is depicted on Plate XXXVIII, page 157.
With Mr. Head, the writer examined many
of the Strigidae confined at the time (July,
1912), in the gardens of the (British) Zoolog-
ical Society. Those that had been caged two
years or more were plainly affected with
choroidal changes, mostly of the disseminated
choroiditic type, the choroidal atrophy and

pigment deposits varying in amount but
nearly always more marked the longer the
birds had been imprisoned.

The general tone of the eyeground in Strix-
flammea is dull gray with bright, clearly out-
lined, orange-red choroidal vessels distributed
all over the fundus, except at the macular
region. At this area the tint is much grayer,
being, in addition, stippled with small, irregu-
lar blotches of orange-red and gray dots.

The macula is also suffused with a gray
reflex. It is situated above the upper end of
the optic disc and nearly in a line with the
long axis of that organ.

The papilla is long and narrow, with pointed
ends, and is apparently made up of coarse,
white fibre-bundles the central portion of
which is covered with minute, brown, pig-
ment grains, that have a distinctly reticulated
appearance. These white fibres border the
nerve-head all around.

The dark-brown, convoluted pecten of the
Barn Owl is much larger than that of the
Tawny Owl. It is also placed farther for-
ward towards the lens than the pecten of the
latter bird. Extending from both sides of
the disc are a few, dull-gray fibres that stretch
a short distance across the fundus and then
disappear.

Two specimens of Strix pratincola and two
of Strix perlata revealed ophthalmoscopic
appearances quite similar to those seen in
Strix flammea, except that the fundi of the
two first-named species are generally of a
deeper gray. All these (four) individuals
were suffering from choroidal changes.

Psittaciformes

Great Sulphur-crested Cockatoo.
Cacatua galerita. (Figs. 98 and 133; mac-
roscopic views.) In this ocular background
there is no visible fovea or macular area.

The medium-sized pecten exhibits rather
broad, rounded convolutions, some 24 in all,
that are joined above by a heavy process or
crest of irregular outline. The latter extends
one-half the length of the free upper border,
joining together nine equal-size double folds.
From this keel-like body the mass of the pec-
ten slopes off to the front, exposing portions

THE FUNDUS OCULI OF BIRDS

of the whitish nerve head, which is dotted
with very small pigment granules.

The ophthalmoscopic appearances of the left
eye of Cacatua galerita, erect image, are por-
trayed in Plate XLI, page 161. The back-
ground is of a fairly uniform, light grayish-blue
color, sprinkled with minute white dots that
are interspersed with many less numerous
but somewhat larger dark gray deposits.
The macular area, at the upper-inner quad-
rant, is an irregularly round, light brownish
area whose diameter is half the disc length.
It is not, as in many Birds, surrounded and
denned by an outer ring; the periphery fades
into the surrounding gray of the fundus. The
upper sixth of the long, pointed papilla is
distinctly visible where it is not covered by
the indented pecten, whose twelve double folds
have a corkscrew termination above. Por-
tions of the disc borders can be seen from
above through the plications, except at its
posterior terminal where the dark-brown mass
entirely covers it. Faint, whitish lines of
opaque nerve fibres extend from the margins
of the upper half of the disc a short distance
across the centre of the eyeground.

Orange-winged Parrot. Chrysotis ama-
zona. Plate XXXIX, page 159, represents
the ophthalmoscopic appearances in the right
eye of this species. The dominant color of
the eyeground is deep gray tinted with buff.
The lower sectors and the peripheral zone
of the fundus are suffused with pink, the
background generally being punctuated with
minute, dull-yellow dots.

The macular area is situated towards the
nasal side of the disc, a little above the
end of the pecten. It is slightly depressed
and enclosed by a rather bright but pale-green
reflex-ring. Extending from the circum-
ference of this circle, slightly above as well as
below, are a few translucent fibres, pale
green in tone; and at its centre is a dark-
gray dot or depression, with a small, faint
halo extending from its upper edge.

The optic nerve-head looks as if it were
composed of coarse, white, opaque fibres,
which form a fringe all around the deeply-
colored pecten. The papilla is long and
boat-shaped, and its outlines can be traced

the whole length of the pecten. Many fine,
gray, opaque nerve fibres extend from the
margins of the papilla, cross the background
of the eye and are eventually lost in the
fundal tissues.

The dark-brown pecten, seen from above,
has a spiral form, with a tag or tail-piece at
the upper end. A lateral view shows it to
be plicated, like a fan. It stands well forward
towards the lens.

The light reflected into the eye from the
ophthalmoscopic mirror does not appear to
disturb specimens of the species at all,
unless it is concentrated on the macular
region.

White-fronted Cuban Contjre. (?)
Conurus ridgway. The writer examined with
the ophthalmoscope the fundi of an individual
four years old that had been an inmate of
Bronx Park for three months. Neither a
one-fifth of one per cent solution of sulphate
of atropia nor a homatrophine and cocaine
mixture had any effect on the size or motility
of the pupil.

The eyeground was generally reddish-
gray; the pecten was large, convoluted and
extended well into the vitreous cavity and
approached the posterior lens surface. There
was no well-defined macular region. The op-
tic entrance was almost covered, and a view
of it obscured, by the base of the pecten.

J£akapo. Owl-Parrot. (New Zealand.)
Stringops habroptilus. In July, 1914, the
writer examined the single specimen then in
the gardens of the Zoological Society at
Regent's Park, London. The bird had, at
that date, been in captivity two years, and
seemed dazed when exposed either to bright
natural or artificial light. The keeper reported
that the bird is very quiet during the daytime
but digs in the sand of his box at night. The
lids have no cilia-like protection — only scat-
tered plumules on the otherwise naked lids.
He has large pupils and a dark brown iris.

The red-brown fundus is fairly easily seen
with the ophthalmoscope without using any
mydriatic. The frontal position of the eyes
(found in all Strigiformes and to which
order the writer believes this species right-
fully belongs) is marked in this animal, and

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 97

Fig. 134. Common Hoopoe (Upupa epops) Xl8.

Fig. 135. Anna Hummingbird (Calypte annas) X31.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

THE FUNDUS OCULI OF BIRDS

the bird evidently possesses binocular vision
as he always looks straight ahead at objects
that he wishes to see distinctly. Plate XL,
page 159, furnishes an ophthalmoscopic view
of the right eye, erect image. The eye-
ground is orange-red stippled all over with
lighter orange dots. The lower half of the
fundus has a large number of minute, dark,
reddish-gray depots of pigment intermingled
with lighter dots; also, a great many cho-
roidal blood vessels run in a vertical direction
over the field of view on either side of the
optic entrance. They become more numerous
towards its lower periphery.

The macula is placed, as in Owls generally,
on the temporal side of the optic papilla,
about one disc-length from its upper end
and half that distance to the temporal or
outer aspect of the fundus. It is a bright,
orange-red area surrounded by dark, red-
gray pigment, like a shadow. There is no
circular sheen around it, such as has been
noted about other avian fovese.

The optic nerve-head is white, and along
its center appears a network of minute,
brown pigment dots clustering around the
sides of the pecten. A few white opaque
nerve fibres extend a short distance on either
side and about the upper end of the disc.

The pecten, of the usual black-brown color,
extends the whole length of the disc. It is
rather straight in its upper half but is more
convoluted towards the lower part, where it
is quite massive and resembles a corkscrew.
This portion of the pecten comes markedly
forward towards the lens so that it more
nearly resembles the same organ in the
Burrowing Owl than in the Parrot; as indeed
the foregoing studies of the fundus oculi
lead unmistakably to the conclusion that
this bird belongs to the Owls rather than
to the Parrots.

Coraciiformes

European Kingfisher. Alcedo ispida.
(Figs. 99 and 113; macroscopic view.) This
remarkable background shows two exten-
sive, well-defined, circular macular regions,
both supplied with a large, deeply pigmented
fovea. The nasal macula is large and

saucer-like. The fovea nasalis is surrounded
by a nebula formed of microscopic dots
that are, however, absent at the lower
nasal third of its margin. About the same
distance down and templewards from the
superior end of the disc, as the deeper fovea
is up and nasalwards, lies the secondary area
temporalis. [In the sketch the wall of the
globe is cut away to expose it.] This tem-
poral macular region is smaller and not so
well defined as the nasal fovea but it exhibits
a distinct pigmented centre surrounded by a
dotted ring.

The large and curious pecten exhibits 17
double folds, two at the superior terminal
of the organ. These 34 convolutions are
very thin (like strips of paper), and through
the wide intervening spaces almost the
whole surface of the optic disc can be seen
and its outlines readily traced. The papil-
lary surface is dotted exactly like the sur-
rounding retina. The crest or free border
of the pecten is quite narrow, and caps the
pectinate mass in a wavy line. The naked-
eye view from above gives a picture much
like a fern frond.

Laughing Kingfisher. Dacelo gigas. The
ophthalmoscopic appearances of this species
are pictured in Plate XLII, page 161.

The fundus oculi is in general of a light
fawn-gray color mingled with irregularly
shaped, white or gray-white dots, except in
the neighborhood of the optic nerve where
it is orange-red, like the glow cast on the
sky by the setting sun.

The optic nerve entrance is long and narrow;
it is white except along its central area, which
is orange-red striped with brown pigment
dots. A large number of opaque nerve
fibres run out on each side of the optic nerve
and at right angles to it.

The pecten is very long and narrow and
has the appearance of a brown centipede.

The macula is very conspicuous. About
half a disc-length from the upper end of the
nerve, towards the nasal side, is a small,
round, dark-brown hole, surrounded by a
very narrow, bright green ring. This circle
encloses a smaller area that is of a darker
gray and devoid of the dots seen at other

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 99

Fig. 136. Yellow-billed Cuckoo (Coccyzus americanus) Xl3.

Fig. 137. Red-shafted Flicker (Colaptes mexicanus) X 12.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

100

THE FUNDUS OCULI OF BIRDS

parts of the eyeground. The fovea nasalis
always appears directly opposite the pupil;
there is no fovea temporalis visible to the
ophthalmoscope.

Common Hoopoe. Upupa epops. (Figs.
134 and 100; macroscopic view.) This medi-
um-tinted fundus exhibits a single macular
region, — a round figure whose diameter is
equal to the extreme width of the papilla.
It is depicted by a dotted fine of pigment
grains that are more numerous below. The
fovea is shallow and not well-defined.

The relatively large pecten has numerous
(about 40) convolutions; it forms a compact
mass that almost obscures the papilla, par-
ticularly when the disc is viewed from
above. It is covered by an ovoid cap that
extends from the ridge-like (upper) free
border about one-fourth of the distance to
the pectinate base, whose full length is more
than four times its extreme width.

Black Hornbill. (?) Spagolobus adratus
An ophthalmoscopic view of the ocular
fundus of this species is pictured as Plate
XLIII, page 163 of this work. The painting
is of the right eye by the direct method.
The shimmering reflections from the trans-
lucent retinal elements of the fundus make
an accurate ophthalmoscopic view some-
what difficult. The principal color of the
eyeground is dull gray, interspersed for some
distance about the optic nerve-entrance
with a mass of fine, opaque fibres that extend
about a disc-length over the fundus. Beyond
the fibres are several dull-colored, choroidal
capillaries that cross the fundal field in a
vertical direction. Near the macular region
the fundus is illuminated by a brilliant
gray iridescence.

The optic disc is a long, white oval, that
extends downward and a little inward towards
the inner or beak side of the head.

The pecten is very large, the lower seg-
ment being carried so far forward behind
the iris that it is difficult to inspect it with
the ophthalmoscope. Instead of the usual
fringe of pigment the pecten presents serrated
margins.

The macular region is quite circular and
is red-brown in color. An inner circle is

dead white, while the foveola is represented
by a dark-red, central spot. There are two
bright rings around the macula of an irides-
cent, blue-green color, the fundus between
the two circlets being a light, luminous gray.

European Nightjar. Caprimulgas euro-
peus. The fundus picture (left eye, erect image)
of this bird is furnished by Plate XX.IV,
page 163.

The eyeground appears orange-red, every-
where stippled with small, red and brown
patches of irregular shape. Scattered about
are several pigmented areas, such as one
sees in the eyes of human subjects with
disseminated choroiditis. This condition,
somewhat modified, is seen in many owls
long confined in zoological gardens or aviaries,
and it seems to be confined to Night Birds,
and to be one of the results of confinement
and domestication. In many respects, also,
the eye of the Nightjar resembles that of the
Strigiformes except that Caprimulgus has
fewer choroidal vessels in the lower half of the
fundus. These are faintly outlined, but they
give to that part of the eyeground a deeper
red than the remainder of the background.

The optic papilla is short and broad.
The antero-posterior view with the mirror
shows it as a dull, grayish-white body large-
ly covered with brown pigment dots. Its
margins, where it is not obscured by the mass
of the pecten, is much lighter in color. Radi-
ating from the sides of the disc, and extend-
ing for a short distance on either side, are
a few white opaque nerve fibres, which are
light gray and become less distinct on the
outer side of the papilla.

Anna Hummingbird. Calypte anna.
(Figs. 101 and 135; macroscopic view.) The
ocular background of this species shows two
plainly marked macular regions, the nasal
fovea being, as usual, the better defined.
This area nasalis is seen as a black spot
entirely surrounded (except at the lower
fourth of its circumference) by a halo of
dark pigment grains. Outside of this is an
untinted zone that, in its turn, is encircled
by a nebulous ring broader below than
above. The tunics of the eyeball are cut to
show the temporal site of the second macular

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

101

region. Figure 135 furnishes an enlarged
picture of this area, which is a duplicate of
the area nasalis except that the fovea is
shallower and not so black, while the pigmen-
tation of the surrounding ring is less marked.
The pecten has 32 convolutions — 16 on
each side — united to a long, narrow sinuous
crest. The fold that constitutes the front of
the free border becomes broader and rounded
as it gradually slopes from the crest to the
superior end of the optic disc. Uncertain
glimpses are gained of the papillary borders
through a few spaces between the more cen-
tral pectinate folds; otherwise the surface of
the optic entrance is entirely obscured.

Cuculiformes

Yellow-billed Cuckoo. Coccyzus ameri-
canus. (Figs. 102 and 136; macroscopic view.)

The single macular region is of immense
size — considerably larger than the untinted
area on the nasal side of the pecten, and
two-thirds as wide as the optic entrance is
long. A nebulous zone of pigment dots
encloses this large sensitive area, the dots
being drawn as distributed everywhere ex-
cept at the upper fourth of the zone, where
they are comparatively few. The fovea oc-
cupies the exact center of the circle and
shows as a dark pigment spot with its upper
two-thirds covered with black granules
closely spread above it fan-wise.

The pecten has about 24 heavy, compact
convolutions that almost completely cover
the optic entrance. They are joined at the
irregular free border above by a translucent,
cigar-shaped band of tissue that extends
the whole length of the crest.

The anterior and pointed terminal of the
papilla approaches to within less than a
disc width of the temporal boundary of the
macular region.

European Cuckoo. Cuculus canorus.
The ocular fundus of this bird, as seen in
living specimens by the aid of the ophthal-
moscope, is depicted on Plate XLV, page
165. The picture is drawn of the left eye;
erect image.

The coloration of the eyeground is gray
with a suggestion of fawn, everywhere show-

ing minute, grayish-white dots. Towards
the lower quadrants of the fundus and in
particular at the extremity of the pecten the
background is suffused with a dull pink.
Near the optic nerve on either side are
several, plainly visible, orange-red choroidal
vessels.

The macula is seen above the disc, towards
the nasal side. This area, slightly red in
tone, appears depressed below the fundal
plane, although no definite fovea is visible
with the mirror.

The papilla is almost completely covered
by the pecten, so that only the outlines of
the former can be seen by the anteropos-
terior inspection of the ophthalmoscope.
Where the papillary margin is visible it
shows extremely white.

The pecten also extends far above as well as
below the disc terminals and projects deeply
into the vitreous chamber. It appears by
the mirror to be a chocolate-brown in color.
Opaque nerve-fibre radiations are seen to orig-
inate at the disc margins, whence they cross
the background and finally disappear from
view at or near the periphery of the field.

Piciformes

Sulphur-breasted Toucan. Rhamphas-
tus lamiatus. As shown in Plate XL VI, page
165, this bird has a dull-gray eyeground (when
it is viewed ophthalmoscopically) rather regu-
larly spotted with whitish-gray dots.

The optic papilla is apparently composed
of short, coarse, white fibres which form a
sort of fringe all round its margins. Along
each of its sides and parallel to its long diam-
eter a few orange-red, choroidal vessels are
seen. Radiating from the papillary circum-
ference are numerous opaque nerve fibres
that extend to the fundal periphery across the
eyeground on all sides.

The pecten is almost black-brown in color
and in shape resembles the same organ in the
Hornbills and the Kingfishers, especially in
the former.

Above the end of the optic nerve entrance
and about half its length to the nasal side are
three dark-brown spots, clustered together
and surrounded by a small gray reflex. This

102

THE FUNDUS OCULI OF BIRDS

area is probably the macular region; at least
it corresponds to its usual locality in other
orders and presents the characters one might
expect, knowing the habits of the animal.

Red-shafted Flicker. Colaptes mexican-
us. (Figs. 104 and 137; macroscopic view).
The ocular fundus of this species presents a
single fovea (or what in Man is called the
oveola) that seems larger than usual; at any
rate the central black spot is more pronounced
than in most Birds. It has no well-defined
macular ring but appears to have a place in
the uniformly dotted retina about half a disc
length above and slightly to the nasal side of
the anterior optic terminal.

The pecten has seventeen double coils (34
single convolutions) on either side of a promi-
nent and rather deep keel or ridge that unites
them above. Of these coils two stand at
right angles to the keel, two are slightly curled
on themselves and present a concavity
towards the posterior free border, while the
remainder look in the opposite direction with
varying degrees of concavity.

Red-headed Woodpecker. Melanerpes
erythrocephalus. (Figs. 103 and 138; macro-
csopic view). The general appearance of
this fundus much resembles that of the Red-
shafted Flicker. It is true that here the
macular field is defined by a boundary of faint
printed dots, but these are hardly distin-
guishable, except at the infero-nasal quad-
rant, from the pigment of the neighboring
retina. In the center of the sensitive area
is a single black spot surrounded by a cloud
of dark granules that are wanting below, in-
tended to depict the fovea.

The pecten has 34 single convolutions. Its
structure also closely resembles that of the
Flicker just described, but the former is
larger, the folds are heavier, and the uniting
keel is wider and deeper.

Gila Woodpecker. Centurus uropygialis.
An ophthalmoscopic view of the fundus oculi
of this bird, as shown in Plate XL VII, page
167, shows it to be dull -gray tinted with
yellow, and nearly uniformly charged with
minute, gray dots.

At the superior termination of the optic
disc (on the nasal side) is a small gray depres-

sion, partly surrounding a central, well-
marked and glistening white dot. Within
this area are, also, several golden yellow dots,
which can be seen only when the reflected
light of the ophthalmoscopic mirror falls
obliquely upon them. Owing to the limited
number of this species that Head and the
writer were able to examine it was impossible
to say whether the punctate deposits last
mentioned are normal or pathological. Fur-
ther investigation of additional specimens,
both ophthalmoscopically and microscopically,
will be necessary to decide the question.

The outlines of the optic nerve entrance
are well defined, and the central area of the
papilla at its union with the pecten is dull
orange stippled with dark brown pigment,
like pepper grains. The papilla is fringed
with coarse white fibres. A large number
of translucent nerve fibres radiate from the
edge of the optic disc on all sides; they be-
come fainter and fainter as they approach
the fundal periphery and finally disappear.

The pecten, of the usual chocolate brown
color, reveals several corkscrew convolutions.
It comes well forward towards the lens, and
presents a massive, club-shaped appearance.
In most respects this fundus picture re-
sembles the eyeground of the Greater Spotted
Woodpecker.

Great Spotted Woodpecker. Dryobates
vel Dendrocopus major. The fundus picture
of this species is seen as Plate XL VIII, page
167. The color of the eyeground is a uni-
formly dull but definite gray, interspersed
with a large number of small, gray dots. Be-
low the optic disc and pecten are a few faint,
orange-red choroidal vessels.

The optic disc is apparently built of a mass
of brilliant, white, opaque fibres, very short
and thick. In the form of radiations from
the margins of the papilla towards the fundal
periphery run many gray, opaque nerve
fibres, that appear to occupy a plane lower
than the white elements of the disc.

The pecten has three corkscrew convolutions
on the disc, while its lower part forms a club-
shaped mass of a deep chocolate-brown color
that appears to come well forward towards
the lens.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 103

Fig. 138. Red-headed Woodpecker (Melanerpes erythrocephalus) X13.

Fig. 139. Western Mockingbird (Mimus polygloltos leucopterus) Xl4.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

104

THE FUNDUS OCULI OF BIRDS

There seems to be only one sensitive central
area. This single macula is, as usual, on the
nasal side of the pecten and has the appear-
ance of a brilliant, white, round dot, the fun-
dus surrounding it being a little darker than
the general color of the eyeground. The sur-
rounding gray area makes the white fovea
stand well forward, almost as if it were actu-
ally situated in the vitreous. No reflex ring
can be seen around it.

Passeriformes. A. Mesomyodi

Derby Tyrant. Pitangus derbianus.
The fundus view of this species, shown by
Plate XLIX, page 169, represents ophthal-
moscopic examinations of three specimens.
The six eyes of the three birds presented pre-
cisely the same ophthalmoscopic appearances.

The eyeground is blue-gray, everywhere
sprinkled with minute, gray dots. These
dots are so closely packed in the upper half
of the fundus that they give it a distinct
silvery appearance. Running at right angles
to either side of the optic papilla are numerous
dull-white opaque nerve fibres. These are
near together and extend well across the eye-
ground.

At right angles to the optic disc towards
the nasal side and a little above its superior
end is a dense, pale-blue, punctate mass that
appears to surround the fovea. A light-blue
reflex ring also encircles this area.

The optic nerve-entrance is long, narrow and
white. Its centre is stippled with a few
brown pigment dots, and it is bordered all
around with symmetrically placed black pig-
ment granules. This pigmented margin
varies a little in individuals. The pecten,
long and narrow, extends well behind the
edge of the pupil so that a portion of it can-
not be seen through the mirror. The upper
part is serrated but the lower half is more of
the corkscrew type. The color is the usual
deep, dull brown.

Passeriformes. B. Acryomodi

European Chimney Swallow. Hirundo
rustica. The ophthalmoscopic appearances in
this species are shown on Plate L, page 169,
and depict the erect image of the right fundus.

The general color of the eyeground is warm
gray, tinted slightly with yellow or buff, and
covered with minute, dull, yellowish dots.
Several pale orange (choroidal) blood-vessels
are seen near the upper extremity of the optic
nerve-entrance.

There are visible two macular regions, one
on each side of and above the upper end of
the disc. They show as small brown areas
or dots in the eyeground. Surrounding the
temporal macula is a slight reflex, apparently
composed of minute, bright gray dots. The
macula on the nasal side is quite devoid of
this reflex-ring.

The optic papilla, long and narrow, tapers
at its upper end. On either side of the disk,
and at right angles to it are a few, fine, dull-
gray opaque nerve-fibres.

The pecten is quite narrow at its junction
with the optic nerve, but it gradually becomes
wider and more massive as it approaches the
lens. It is of the usual chocolate-brown color,
and is convoluted.

Western Mockingbird. Mimus poly-
glottos leucopterus. (Figs. 105 and 139; mac-
roscopic view). In this fundus are seen two
sensitive areas. The area nasalis, lying above
and anterior to the superior end of the optic
entrance about half the length of the papilla,
is seen as a black spot capped on its temporal
aspect by a semi-circle of large pigment
grains. The whole macular region is not
only bordered by pigment but the intervening
zone is, in the nasal three-fourths, also
sprinkled with minute granules. The area
temporalis is placed almost directly posterior
to but much farther from the upper end of
the disc than the nasal fovea. It is evidently
shallower, is less plainly outlined and the
foveola is not as large. [The black line run-
ning along the left side of the large figure
indicates that a segment of the globe has been
removed — to show the temporal macula.]

The very long, narrow pecten has 52 single,
compact convolutions that everywhere hide
the optic entrance. A moderately deep and
wide keel unites the pectinate folds along the
upper free border of the pecten almost to its
junction with the superior, pointed end of
the disc.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 105

Fig. 140. Bluebird (Sialia sialis) Xl8.

Fig. 141. California Shrike (Lanius ludovicianns gambeli) X 12.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

106

THE FUNDUS OCULI OF BIRDS

American Mockingbird. Mimus poly-
glottos. The ophthalmoscope shows the pre-
valent coloration of the fundus in this species
to be a clear, blue-gray. Thickly scattered
over the background are irregularly shaped,
whitish-gray dots or granules that in the
upper sectors of the field give the fundus an
unusually bright gray appearance.

Near the upper extremity of the optic
papilla and towards the nasal side is the
macula. This area is darker blue than its
surroundings, while its centre (the fovea) is
marked by a bright white dot which, again, is
enclosed in a green reflex. This greenish
reflex-ring has a striated appearance, the
striae being quite translucent and convergent
towards the fovea centralis.

The optic disc is long and narrow; the visible
portion is brilliant white and its margins are
traceable on either side the whole length of
the pecten. Radiating from the boundary
of the nervehead are many long, opaque
nerve fibres that extend over the eyeground
to its periphery.

The pecten is, as usual, of a chocolate-brown
color; it is long, somewhat club-shaped and
extends well behind the margin of the iris,
so that its outlines are not entirely visible by
the mirror through the undilated or only
partially dilated pupil.

The fundus of the Cuban Mocking Bird
(M. orpheus) is similar in every respect to
that of Mimus polyglottos.

Bluebird. Sialia sialis. This was one
of the earliest species examined ophthalmo-
scopically by the writer, and he was so struck
by the wonderful blue coloration of the ocular
background that the question arose in his
mind as to whether there might not be some
connection between plumage tints and fundus
coloring. That query was soon answered in
the negative but the beautiful blue shades
in the eyeground of Sialis are still to be
admired.

As seen in Plate LI, the ophthalmoscope
shows that the general blue-gray coloring of
the eyeground is modified by numerous, pin-
point dots. The punctate deposits near the
periphery assume a more or less dull-golden
or orange tint, a condition also noticed just

below the pecten. The elongated, ovoid
optic disc is white (quite woolly at its margins)
and covered almost entirely by the convo-
luted pecten, which is very large when com-
pared with the size of the eye. A portion of
the unusually extensive pecten cannot be
seen through the small pupil. It is of the
usual dull-brown color, and has "frilled"
borders. On the inner or nasal side and near
the lower part of the optic disc is an orange-
red area, containing chiefly choroidal vessels
with black pigment grains between them.
This red area extends a little to the temporal
side of the disc, subsequently merging into
the dull orange color below. On either side
of the disc and radiating from it, are numer-
ous filiform nerve fibres which cross the back-
ground almost to its periphery. In an area
a disc-length to the nasal side of the papilla,
the white dots of the fundus are fainter and
much closer together than elsewhere; and in
this region, also, there is a reflex plainly
marked. Here, if in any part of the fundus,
is the fovea or macula, but it is not sufficiently
well defined to be certain of it.

Figures 106 and 140 demonstrate quite con-
clusively that in the fundus of Sialia sialis
there are two macular areas, symmetrically
placed above and on either side of the pointed
end of the papilla. The area nasalis is removed
about half a disc length; the fovea temporalis is
somewhat more distant from the same point.
The nasal macular region is larger and more
plainly marked; it is surrounded by a dotted
ring, incomplete above; the corresponding
foveola is represented by a black spot crowned
by pigment grains. More than half the inter-
vening zone is lightly strewn with minute,
dark granules.

The heavily -built pecten is composed of 19
thick, rounded, double folds — or 38 con-
volutions. A comparatively massive, paddle-
shaped crest surmounts these and extends
along the whole of the upper free border.
The major axis of the papilla makes with a
line joining the two foveolse an infulapapillary
angle of about 70°. There is nothing to be seen
of the nerve head from above.

Wheatear. Saxicola cenanihe. The color
reproduction shown in Plate LII, page 171,

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS 107

furnishes an exact view of the ophthalmo-
scopic appearances of the fundus oculi of this
species. It is of the left eye, erect image.
The general fundal coloration is pale gray,
with a dense mass of grayish white dots
permeating the entire background.

Slightly above the upper termination of the
optic nerve, and towards the nasal side of the
pecten, is a well-defined, round, white area,
(the macula and fovea) much larger than the
small spots that cover the whole of the sur-
rounding, duller eyeground. This white area
is inclosed by a brilliant, bluish-green circle,
which appears more prominent and iridescent
in nature than is depicted in the drawing.

Little can be seen of the optic papilla be-
cause it is almost entirely obscured by the
pecten. However, it is long and narrow, with
an irregular outline.

On the nasal side of the nerve-head are a
few short, orange-red, choroidal blood-vessels
with a few dots of pigment, like pepper grains,
sprinkled between them. Extending from
both margins of the optic disc across the
fundus to the periphery, are numerous fine,
opaque nerve fibres, the upper ones (on the
nasal side), terminating at the macular area.

The pecten, red-brown in color, long and
narrow, appears to be twisted on itself like a
rope or a corkscrew. Its inferior end extends
beyond that part of the eyeground shown in
the picture, but it probably comes well for-
ward towards the posterior surface of the
lens.

English Nightingale. Aedon megaryn-
cha. The ophthalmoscopic appearances of
this species is almost identical with those of
the Wheatear (see Plate LII, page 171), ex-
cept that in Saxicola the macular region is
not so well defined.

California Shrike. Lanius ludovicianus
gambeli. (Figs. 107 and 141; macroscopic
view).

There are two macular regions in the fundus
of this bird, similar in every detail to the same
areae in the Bluebird.

The optic papilla is, however, longer and
somewhat narrower in Lanius, and the more
extensive pecten exhibits folds joined along
its free border by a rounded crest that from

above takes on the shape of a carrot. The
major axis of the long ovoid disc projected
until it meets a line crossing the floor of the
concave fundus and joining the two foveolse
would subtend an (infulapapillary) angle of
about 110°.

Passeriformes. B. Alaudidae

European Titlark. Anthus pratensis. A
healthy adult male individual of this species,
about three months in captivity, obtained
from a dealer, was examined by the writer in
the laboratory of St. Luke's hospital. The
pupils were unaffected by one drop of a 1%
sol. of atropia instilled 48 hours previously.
The bird was strongly hyperopic and very
slightly (about 0.33 D.) astigmatic, the skia-
scope showing 3.50 D. of HAS in each eye.

The ophthalmoscopic examination revealed
no opacities in the ocular media.

The pecten is of the usual black-brown
color; it is large and spiral, filling the whole
pupillary area when examined with the mir-
ror, and almost entirely obscures the outline
of the optic papilla from which it springs.

The background is of a fine, pepper-and-
salt character with a very few opaque nerve
fibres radiating from the disk. Scattered
over the field are many fine sparkling points
like minute grains of cholesterine. These
are also to be found in the macular region,
which is definitely outlined directly in the
axis of vision and covers a space about J^ of
a disc-length. The mirror does not show a
second area of acute vision.

Passeriformes. B. Fringillidce

British Linnet. Linota cannabina. The
indirect ophthalmoscopic examination of an
imported individual, in captivity a year or
less, shows a pecten that obscures a view of
the fundus details, but the prevailing color
of the eyeground is readily seen to be a beauti-
ful, light, gray-blue beset with whitish dots.

British Goldfinch. Carduelis elegans.
The fundus of this bird as seen by the indirect
method — it was extremely difficult and un-
satisfactory to make an ophthalmoscopic
examination by the erect image — showed an
eyeground that resembles that of the Linnet

108

THE FUNDUS OCULI OF BIRDS

Fig. 142. American Crow (Corvus americanus) X8.
Macroscopic Appearances of the Fundus Oculi in the Preserved Eyes of Birds.

in being uniformly light blue-gray. The
pecten obscured most of the field.

British Siskin. Chrysomitris spinus.
One of this species, obtained from a dealer
and said to have been captive for six months,
was examined by the indirect method through
the small and undilated pupil. There was a
relatively large pecten which made it impos-
sible to outline the optic nerve-entrance clear-
ly or to determine the fundus details. How-
ever, the prevailing color of the eyeground
was light gray-blue, more or less regularly
besprinkled with minute, yellow-white dots.

House Sparrow. Passer domesticus.
The ocular fundus of this typical species is
pictured as Plate LIII, page 173 the result
of the ophthalmoscopic examination of numer-
ous specimens. The dominant coloration of
the eyeground is pale-gray covered with very
fine white dots, closely packed together at the
macular area. They form a lighter zone a
little above the upper extremity of the pecten

and towards the nasal side of the disc. From
the circumference of the optic disc a large
number of rather long, opaque nerve fibres
run in radial fashion towards the periphery
of the fundus.

The papilla appears, when visible, to be
composed of irregularly shaped, brilliant,
white bundles; it can barely be outlined with
the mirror except at the upper (and narrow)
end of the pecten.

The pecten has a deep red-brown color, and
its free extremity is long, narrow and of the
corkscrew type. The lower segment of the
organ extends well forward towards the lens
and, being large and massive, completely
covers the pupil and makes it impossible to
obtain a lateral view.

Varied Bunting. Cyanospiza versicolor.
Plate LIV, page 173, represents the ophthal-
moscopic appearances of this species. The
prevailing color of the eyeground is dull gray
shading to buff. It is covered all over with

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

109

very minute, grayish-white dots. These dots
coalesce at the macula where they form a soft,
round area bordered by a light reflex. The
single macular region and fovea are situated
a little above the upper end of the pecten and
towards the nasal side of the optic nerve.
The pecten, very large and massive for the
size of the eye, is of the usual chocolate-
brown color; it is more or less club-shaped,
and extends well forward towards the lens.
At times it quite fills the area of the pupil, so
that the fundus is difficult to explore. The
pecten, whose outline is very irregular, covers
the papilla entirely so that it appears to
spring directly from the retina without show-
ing the white disc margin found practically in
all birds. From the sides of the apparent
root of the pecten a few, whitish, opaque
nerve fibres cross the field of view.

Passeriformes. B. Tanagridce

Scarlet Tanager. Piranga erythromelas.
The dominant coloration of the eyeground in
this species — readily seen by aid of the in-
direct method — is a clear, bright gray-
brown, sprinkled with numerous, glittering
whitish-yellow points.

Law Bird of Paradise. Parotia lawii.
Plate LV, page 175, gives an ophthalmoscopic
picture of the fundus of the left eye, erect
image.

The eyeground appears yellowish gray, or
khaki color, almost uniformly covered with a
dense mass of minute white dots, that are
smaller and denser at the macular region. A
few dull-red choroidal capillaries are visible
on the lower part of the fundus near the
periphery.

The optic nerve head, dull-white, long and
narrow, has a rounded upper end. Its entire
central area appears as if it were a mass of
fine, brown pigment dots.

The pecten is exceptionally long, rather
narrow, spirally arranged and extends beyond
the range of vision through the undilated
pupil. It is similar in many respects to the
fundus of the Common Pigeon.

To the nasal side and a little above the end
of the disc is the macular region, which appears
as a dull-brown, crater-like depression bound-

ed by a white mass of (reflex) striations.
Opaque nerve fibres radiate from both sides
of the disc but finally disappear as they
approach the boundaries of the fundus.

Passeriformes. Corvidm

Blue Jay. Cyanocitta cristata. The fun-
dus appearances as revealed by the ophthal-
moscope in the left eye of one of this species
is depicted as Plate LVI, page 175. The
general color of the eyeground is a slate-gray,
with an added pale-yellow tint in the lower
half of the eyeground. The entire field is
besprinkled with irregularly shaped, light-
gray dots, giving it the appearance of a rough
and rather coarse surface, especially near the
macular area where the dots are more closely
packed in the shape of a bright, circular
patch.

The optic nerve-head is quite white and of
oblong shape. Several orange-colored, cho-
roidal capillaries are visible in this region,
covered with minute, brown, pigment dots,
like black pepper grains. Sprinkled about
each side of the optic disc is a large number of
opaque nerve fibres that extend across the
fundal field.

The pecten, of the usual chocolate-brown
color, is rather irregular in shape at its supe-
rior extremity. From above downward it
looks like a tarred ship's cable, becoming
larger as it approaches its union with the
papilla. The length and thickness of this
organ (compared with the size of the eye and
pupil) make it difficult to follow its outlines
throughout. The superior end appears to
come well into the vitreous cavity and to
reach the lens.

Steller Jay. Cyanocitta stelleri. (Figs.
Ill and 109; macroscopic view). The ocular
background of this species exhibits a moderate-
sized, though well-marked, single, circular
macular region. The foveola is shown as a dark
spot crowned by minute pigment grains that
mingle with a similar pigment ring of granules
that serve as a boundary for the whole region.
There is a small, kidney-shaped space be-
tween these two collections of dotted pig-
ment that seems free of color. The centre of
the fovea is slightly above and about half a

110

THE FUNDUS OCULI OF BIRDS

disc-length from the anterior end of the optic
entrance.

The long and wide pecten has 54 single con-
volutions, and in shape resembles the same
organ in the Shrike, except that from the
center of its crest rises a short spine easily
seen in both figures. The optic papilla is
almost completely hidden by the mass of the
marsupium.

American Crow. Corvus americanus.
(Figs. 108 and 142; macroscopic view). There
is in the background of this species an area
of acute visual perception represented by a
retinal bar or band at whose middle point is
seen a well defined fovea, the center of a macu-
lar region formed by a widening of the band
itself. The band stretches horizontally across
the fundus and is centrally located in the
field of view. It is of medium width, out-
lined by a uniformly dotted line above, but
less distinctly below by a string of minute
granules that more or less tint the lower half
of the band itself. The macular region is
formed by a widening of the sensitive band to
form an oval-shaped region.

The superior end of the papilla is one-half
its length from the foveola.

The large pecten (three-fourths the length
of the retinal band) is formed of about 52
uniformly compressed convolutions joined
at their free margins, above, by a shallow,
dumb-bell-shaped crest that slopes gradually
from behind forwards.

If the major axis of the papilla — obscured
by the pectinate mass — were projected to
meet the temporal end of the retinal bar it
would describe an (infulapapillary) angle of
about 60°.

European Carrion Crow. Corvus
corone. The writer examined in the Labora-
tory of St. Luke's Hospital, Chicago, an
adult male of this species, imported from
Germany. He had been in captivity about
a year. Both eyes were healthy. He used
his nictitating membrane freely on the ap-
proach of light to the eye. The pupils varied
in diameter from 2 to 4.50 mm. A single
drop of 1% solution of atropine sulphate into
each eye produced no effect on the size or
movements of the pupils during the following

48 hours. The same negative result was ob-
tained by the use of a one-fifth per cent solu-
tion of hyoscin and by a mixture of homatro-
pine and cocaine. Skiascopy in the dark
room showed, both before and after the use
of atropia, a hyperopia of 2D.

By the direct method the background
appears to be almost uniformly dark red-
brown. The macular region is seen with
difficulty.

The optic disc is a long, white oval with
the pecten a very black, corkscrew-like organ,
apparently changing place and shape rapidly
under examination.

Common British Blackbird. Turdus
merula. The ophthamoscopic picture of this
species is reproduced as Plate LVII, page 177.
It shows the eyeground as seen in the left eye
by the direct method. The general tint is a
slaty-gray with a uniform sprinkling of tiny,
white dots. There is no visible macular
region, but the whole fundus is covered and
its coloring greatly modified by numerous,
linear, opaque fibres that arise from the disc
margins throughout and run across the entire
fundus to the extreme periphery. A few
faint, yellow-red choroidal vessels are seen on
either side of and parallel to the moderately
long and narrow papilla. The upper two-
thirds of the disc is about half covered by the
club-shaped pecten, which is apparently com-
posed of very few folds. The massive, choco-
late-colored, posterior end of this organ en-
tirely obscures the lower third of the nerve-
head, while the upper half of the former has
a light brown margin on its nasal aspect, and
seems to be only in part attached to the nerve-
head beneath it.

Raven. Corvus corax. The fundus picture
(right eye) shown by Plate LVIII, page 177,
represents the (similar) appearances in a
number of specimens examined with the
ophthalmoscope by Mr. Head in the London
Zoological Gardens and by the writer in the
aviary of the Bronx Park, New York.

The eyeground is a light fawn sprinkled
with dots about three shades darker than the
ground color. Mixed with the dark dots
are numerous white ones, seen especially when
a strong light is thrown upon the fundus.

THE FUNDUS APPEARANCES IN VARIOUS ORDERS OF BIRDS

111

About three disc-breadths from the upper
end of the disc on the inner side is a well
marked, bright reflex of a greenish-blue
tinge. It is irregularly oval in shape and
seems to be composed of a number of very
fine fibres. In the center of the reflex is the
macula, a small, dark, crater-like depression,
brown in color. The disc is chalky white,
and gives one the impression that it is com-
posed of many opaque nerve fibres packed
closely together. From the disc margins
there radiate a number of fine optic nerve
fibres that extend across the eyeground. In

the lower part of the fundus, associated with
a number of orange-red dots, are a few orange-
red choroidal blood-vessels, several of the
latter being distributed along either side of
the disc.

The pectens in all the Ravens examined
were of similar shape and of the usual dark-
brown color. They were very thin and nar-
row at the disc but assumed a club-shape as
they approached the lens where they were
darker in color. The pecten comes well
forward and appears at times to press against
the posterior capsule of the lens.

Chapter X
CLASSIFICATION OF THE OCULAR FUNDI OF BIRDS

The particolored avian background, as seen
by the ophthalmoscope, although of great
variety, may be divided into two major
categories and each of these into five sub-
divisions, as follows:

A. The avascular fundus, in which there
are no visible retinal or choroidal blood-
vessels.

This class resolves itself into (a) those
avascular eyegrounds in which the predomi-
nant color is light gray or gray-blue. These
fundi are comparatively rare, but examples
of them are found in the Varied Bunting
(Plate LIV) and the Ipecaha Rail (Plate
XIII).

(b) Dark gray, deep gray-blue or slate-
colored avascular fundi are quite common.
The Harlequin Quail (Plate VIII), English
Sparrow (Plate LIII), Derby Tyrant (Plate
XLIX), Brush Turkey (Plate VII), Yarrell's
Curassow (Plate VI), Sulphur-crested Cocka-
too (Plate XLI), and the European Bittern
(Plate XXI) are samples. The fundi of the
Crested Coot (Plate XII) and of the Black
Hornbill (Plate XLIII) belong to this sub-
division but they also show a greenish tinge.

(c) Yellow, orange and orange-red bloodless
fundi belong almost exclusively to Night
Birds, or to those that use their eyes for
both diurnal and nocturnal visualization.
Such fundi are seen in the Apteryx (Plate
IV), Gannet (Plate XXIX), and the Black-
footed Penguin (Plate XIV). The corres-
ponding class of vascular fundi is a much
larger one.

(d) Fundi of a brownish or russet color,
showing no vascular supply, are rather com-
mon. Examples are seen in the Amazon
Golden Parrot (Plate XXXIX), South Amer-

ican Ostrich (Plate II) and the Cassowary
(Plate III).

(e) Bicolored or multicolored fundi devoid
of visible blood-vessels are but infrequently
encountered. The fundus of the Nubian
Ostrich (Plate I) is mostly of a light chocolate
shading to red; also the Bluebird (Plate LI)
exhibits a background mostly light gray-blue
but has also a small red-brown area or zone
dotted with black.

B. The vascular fundus oculi is one in
which the choroidal capillaries show more or
less distinctly. In some instances the blood-
vessels are barely visible; in others they
cover the whole background and are the most
conspicuous objects in it. The vascular fun-
dus is subdivided like the avascular back-
ground.

(a) Light gray or gray -blue fundi, more
common than A (a), are found in the Wheat-ear
(Plate LII), the Cormorant (Plate XXVIII),
and the Glossy Ibis (Plate XXIII).

(6) Dark gray, deep gray-blue or slate-
colored vascular fundi constitute the com-
monest examples of colored fundi so far seen
by the writer. They are found, among
others, in the European Cuckoo (Plate XLV),
the Wonga Wonga Dove (Plate IX), the
Puffin (Plate XV), Sulphur-breasted Toucan
(Plate XL VI), Spoonbill (Plate XXV), Great
Spotted Woodpecker (Plate XLVIII), Blue-
crowned Jay, with a greenish tinge (Plate
LVI), Common British Blackbird (Plate
LVII), the Night Heron (Plate XX), Ameri-
can Jabiru (Plate XXIV), Law Bird of Paradise
(Plate LV), Lammergeier (Plate XXXII).

(c) Yellow, orange or vermilion fundi show-
ing choroidal blood-vessels are, as in the A(c)
class, found almost entirely in birds with

[ 112 ]

CLASSIFICATION OF THE OCULAR FUNDI OF BIRDS

113

nocturnal habits. Among them are the Bra-
zilian Boatbill (Plate XXII), Kakapo (Plate
XL), and the Barn Owl (Plate XXXVIII).

(d) Vascular fundi whose general colora-
tion is brown, brownish or russet are also fairly
common. The White-bellied Sea Eagle (Plate
XXXIV), Gila Woodpecker (Plate XL VII),
Laughing Kingfisher (Plate XLII), Little
Bustard (Plate XXXVI), Raven (Plate
LVIII), Stone Plover (Plate XVII), Great
Blackbacked Gull (Plate XVI), Blue Snow
Goose (Plate XXVII) and the Chimney
Swallow (Plate L) are among them.

(e) Bicolored or multicolored vascular fundi
are commoner than those classed under A (e).
The vascular eyeground of the Martineta
Tinamou (Plate V) is brownish below and
light gray above; its color scheme reminds
one of the ocular background (when seen
ophthalmoscopically) of some mammalian
fundi. The Australian Pelican (Plate XXX)
has a fundus oculi which is russet below
gradually shading to grayish above. The
eyeground of the Kagu (Plate XVIII) is also
reminiscent of mammalian color mixtures; the
lower half of the background is a well-marked
red-brown dotted with black pigment, while

the upper segment is a sky blue. The lower
two-thirds of the fundus oculi of the Brazilian
Seriema (Plate XIX) is brownish, the upper
third slate-blue. The Bald Eagle (Plate
XXXIII) has also a mixed fundal coloration;
being dull red-brown below and mottled gray
above. Finally, the eye of the nocturnal
Nightjar (Plate XLIV) mimics to some extent
the fundal color distribution in the background
of certain of the night-prowling mammalian
Carnivores, being dark orange-red below and
light orange above.

In the above classification the colored dots
that besprinkle the fundus picture of practically
all Birds (and represent, probably, the colored
droplets of the retina) are not considered.
However, both directly and by contrast they
greatly modify the color impression made
upon the observer, and especially when they
are large and numerous, influence the general
chromatic effect. In some instances, their
number and distribution are such as to deter-
mine the verdict of a first glance, and the
observer must be on his guard not to mistake
these accessory pigment points for the solid
background of color which one finds in all
avian fundi.

Chapter XI

THE OCULAR FUNDUS OF BIRDS IN ITS RELATION TO

A CLASSIFICATION OF AVES

The writer is well aware of the controversies
so easily provoked in that zoological storm
centre, the systematic classification of Birds,
but he believes that as the fundus appear-
ances in wild species are probably invariable
and that, as the evidence so far produced
shows, each species exhibits a background
picture distinct in one or more particulars
from every other species, it is possible to
identify many of them by the use of the oph-
thalmoscope alone; in other words, in the
classification of Birds the fundus details,
including the varied coloration of the eye-
ground, should be considered quite as much
as the histology of any organ or division of
the body.

The extent to which these taxonomic indi-
cations correspond to the orders of any par-
ticular classification cannot, in the absence of
a complete or nearly complete investigation,
now be determined. In the opinion of the
writer, however, there are certain facts that
have arisen in the course of this preliminary
research that are worth discussing for the light
they throw upon and the aid they may give
to a systematic arrangement of avian species.

That the eyegrounds of the Ratite orders
present peculiarities that distinguish them
from the Carinatoe is evident at a glance. On
the other hand there are the usual differences
between the acarinate species. The colora-
tion of the fundi and the characters of the
pectens in Rhea (Plate II) and Struthio
(Plate I) bear a close resemblance. The
ocular fundus of the Cassowary (Plate III)
is more closely allied to that of the Kiwi than
to the Nandu. The ocular background of the
Tinamou is decidedly acarinate and this fact,

with other taxonomic indications, justify,
from the ophthalmoscopic viewpoint, its in-
clusion in that subclass.

The Apteryx is so decidedly a nocturnal
animal - — especially in the use of its eyes for
distinct vision both in the distance and near
— that one is not surprised to see so much
yellow in its fundus coloration. There are
so few exceptions to the rule of the yellow-
colored fundus in Night Birds that one may
confidently assert that the amount of this
color in avian (one might say in all verte-
brate) fundi is in direct ratio to the propor-
tionate use a given species makes of its visual
powers after sunset. When a bird and his
ancestors (in the evolutionary sense) have
used their eyes for distinct visualization
largely or exclusively at night the fundus tint
is nearly always yellow or orange.

Applying this rule to carinate Night Birds
we find many consistent and marked ex-
amples of it. For instance, all the Strigi-
formes so far examined have a preponderance
of yellow in their eyegrounds. Without
carrying this assertion too far we note that
in semi-nocturnal Owls, like Strix flammea
(Plate XXXVIII), the red tints overpower
the yellow and a shade of orange results.

Still more suggestive are the fundal con-
ditions seen in the Owl Parrot, Stringops
habroptilus (Plate XL). Compare the fun-
dus, especially its yellow color and the posi-
tion of the (temporal) area centralis, first
with that of any Owl and then with Psitticus
amazona; undoubtedly, so far as the eyes are
concerned, they belong to the former.

Another observation of avian fundi seems
to show that an admixture of yellow (in the

[114]

CLASSIFICATION OF AVES AND THE FUNDUS OCULI

115

form of an orange-red coloration) may be
present to indicate not so much recent as
former, i. e. atavistic, night habits long since
abandoned by the species.

This almost universal occurrence of yellow
or orange-tinted fundi in Night Birds leads
one to speculate as to the cause of a different
coloration in species that, during historic
times at least, have used their eyes largely or
exclusively after dark. At least some of the
Ardeiformes furnish such examples. The fun-
dal coloring of Nycticorax nycticorax (Plate
XX) has no yellow in it; nor has the Boatbill
(Cancroma cochlearia), although both fundi
are evidently so closely allied that one might
well believe that they are both Herons.
Probably the Night Herons have adopted an

exclusively nocturnal life at such a recent
geologic period that the evolutionary tissue
changes necessary to produce the yellow fun-
dus tints have not yet been brought about.
The same remark is applicable to the Bittern
(Plate XXI).

So far as examined, the decidedly nocturnal
Caprimulgidae also have yellow or orange
fundi. The eyeground of the European
Nightjar (Plate XLIV) is a conspicuous and
typical example of the colored fundus of a
true Night-feeding bird.

The arrangement of the centres of distinct
vision, the fundus tints and the pectinate
tissues of the larger Acciptriformes present a
decided ophthalmoscopic resemblance in all
the species so far examined by the writer.

Chapter XII
RELATIONS OF REPTILIAN TO AVIAN FUNDI

The colored illustrations of three eyegrounds
of reptiles are published by the aid of Mr.
Head and through the courtesy of Mr. Lind-
say Johnson. In this text are also included,
for purposes of comparison, two black-and-
white drawings of mammalian fundi. One of
these, the Common Hedge-Hog (Fig. 143)

Fig. 143

Fundus Oculi of the Common Hedgehog.
(After Lindsay Johnson.)

reminds one of the Indian Cobra (Plate LXI),
while the fundus view (Fig. 144) of the Vir-
ginian Opossum suggests the background of
the Horned Toad (Plate LX). In other
words, these two reptilian fundi have more
marked affinities with other vertebrate classes
than with Birds. On the other hand, were it
not for the absent macular region and the
greater prominence of the radiant, retinal
nerve fibres, the ocular fundus of that noctur-
nal lizard, Hemidactylus turcicus (Plate LIX)
might be regarded as an avian form, rather

closely related, for example, to the Kiwi
(Plate IV).

A reference to the probable evolutionary
connection between Birds and certain sub-
orders of Reptiles, as indicated by their
ophthalmoscopic pictures, has already been
made. It may eventually transpire, as indi-
cated by this "straw" of evidence, that the
Geckotidce are comparatively near relatives
of the primitive Bird, while other lacertilian
suborders and the Ophidia are as far removed
from them as the Marsupials.

A detailed description of the three reptilian
eyegrounds, represented in the Atlas by
colored reproductions, now follows.

Fig. 144

Fundus Oculi of the Virginian Opossum
(After Lindsay Johnson.)

[116]

THE RELATIONS OF REPTILIAN TO AVIAN FUNDI

117

Reptilia
Turkish Gecko. Hcmidacfylus turcicus.
Erect image; left eye. The fundus appear-
ances (Plate LIX) of this nocturnal lizard
remind one of the Kiwi (Plate IV). The
orange-red background is uniformly dotted
with dark spots, while the circular papilla is
completely obscured by a chocolate-brown

Fig. 145
Pecten of a Turkish Gecko (Hermidactylus turcicus).

pecten, whose pointed free end projects a
medium distance into the vitreous. There
are no signs of retinal or choroidal vessels.
Clearly defined, white lines (opaque nerve
fibres) radiate from the disc margins, giving
the effect of a halo about the central zone of
the picture.

A lateral view of the Gecko pecten is seen
in Fig. 145; it is suggestive of a similar view of
the Apteryx pecten (Fig. 27).

Horned Toad. Phrynosoma cornutum.
Plate LX. Left eye. Erect image. The
color of the fundus oculi is a dark slate, irregu-
larly strewn with minute, whitish dots of
various sizes. There is an ill-defined macular
region.

The pear-shaped, grayish papilla has a
white margin, from which short fibres of un-
equal length radiate towards the periphery.
A single central (?) artery seems to originate
from the nervehead and with its six branches
— two on one side of the disc, four on the
other — is supplied mostly to the lower half
of the eyeground. Above, a small branch
anastomoses with a twig that runs from the
periphery of the field.

Indian Cobra. Naia tripudians. Plate
LXI. Left eye. Erect image. The general
coloration of the fundus of this Snake is light
gray-blue, sparsely dotted with pigment of a
similar but deeper color. The whole back-
ground is regularly covered with opaque nerve
fibres whose radiate disposition reminds one
of Merula (Plate LVII). From the button-
like optic disc arise three vessels, apparently
two arteries of small size and one (larger)
vein. The centre of the papilla shows the
remains or the undeveloped tissues of a
pecten.

Chapter XIII

COLORED DRAWINGS OF THE FUNDUS
OCULI OF BIRDS

Efforts to duplicate exactly the paintings made by
Mr. A. W. Head for this Atlas have been attended
by difficulties that have arisen chiefly from the fact
that precise duplication of minute details and shades
of color (of minor importance in the usual forms of
color reproduction) were regarded as essential in this
investigation. However, these impediments were,
after many trials and the exercise of much patience on
the part of the publisher's officials, finally removed and
the writer now believes that the following plates faith-
fully represent not only the varied and beautiful
coloration but the complex tissue formations revealed
by the ophthalmoscope in the ocular background of the
avian and reptilian species herein depicted.

For the convenience of the reader a brief description
of each fundus drawing has been placed on the page
opposite each plate, a more complete description of
the ophthalmoscopic appearances, as well as their
relations to other fundus views, being given in Chapters
IX and XII.

11!)

RATITvE

Struthioniformes

Nubian Ostrich. Struthio camelus. Plate I.

The general color of the eyeground is dull red, besprinkled with
lighter-red, round dots and gray granules. The lower half of the
fundus appears somewhat grayer in tone than the upper sectors.
This appearance is probably due to the numerous opaque nerve-
fibres that extend from all sides of the papilla as a centre across the
fundus to the periphery of the ocular background. The red colora-
tion of the fundus is seen to be more intense towards the upper half
of the eyeground. The optic nerve entrance is very broad and oval
in shape. The margins of the nerve head are very white and it is
possible with the mirror to see all around the pecten. The centre of
the disc, including the parts near the root of the pecten, are stippled
with minute brown pigment dots, like black pepper grains. The
pecten presents the appearance of a number of dull, dark, sepia-
brown tubercles. It does not project far forward into the vitreous
cavity, while its outlines and contour may be distinguished both
above and below the disc. The pectinate margins are formed of
round, ovoid projections. The macula is not very striking in appear-
ance, and takes the form of a crescentic arrangement of minute,
gray dots. It is seen towards the nasal side of the disc near its
upper end.

Rheiformes
American Ostrich. Rhea americana. Plate II.

The coloration of the fundus as a whole is buff, merging into dull
red at the periphery. It is stippled all over with minute dots of a
lighter tint.

The optic disc is made up of white and coarse nerve bundles that
exhibit a faintly defined, fringe-like border all around its margins.
Radiating for a distance of about two disc-breadths across the fundus
are a few, dull-gray, opaque nerve fibres that finally disappear into the
background.

The macula is situated slightly above and to the nasal side of
the optic papilla. It is somewhat grayer than the surrounding
eyeground; above (towards the outer side) and below the fovea are
a, few pale, bright green reflex lines.

The pecten is a massive organ with saw-like margins, the serra-
tions being of a lighter brown than the central body. The lower part
of the pecten is somewhat club-shaped, and comes well forward
toward the posterior capsule of the lens. Between the projecting
teeth of the pectinate serrations may be seen a slight stippling of
pigment-like black pepper grains.

120

RATITjE

Struthioniformes

Plate I

Struthio camelus

Rheiformes

Plate II

Rhea americana

RATITjE

Casuariiformes

Westerman Cassowary. Casuarius occipitalis. Plate III.

The fawn-colored eyeground is covered with a minute, silver-
gray stipple, in the form of fine, short lines with their long axes
running in a vertical direction. As these dotted lines approach the
macular region they become more and more convergent until they form
a brilliant cluster at the fovea. There is no visible line of demarca-
tion or reflex ring separating this area from the general fundus area.
There are no visible choroidal vessels or opaque nerve fibres.

The optic disc is long and boat-shaped, with a reddish, appar-
ently concave centre. It is uniformly sprinkled with darker red dots,
which, as they approach the margin of the papilla, are more closely
packed, and give the appearance of a shadow cast all about the
inner edge of the disc. The margins of the nerve-head are dis-
tinctly white, but they have not the "fibrous" appearance seen in
most avian backgrounds.

The chocolate-brown pecten, much broader at its base than at the
apex, resembles a corkscrew, its lateral elevation being not unlike a
cockscomb, with its six serrations rounded off at the apex. Two
central serrations come well forward towards the lens.

Apterygiformes
Mantell Apteryx. Apteryx mantclli. Plate IV.

The ocular background is uniformly orange-red, somewhat
mottled with brown. The brilliant, white, round disc is surrounded
by short, opaque nerve-fibre layers not entirely covered by the
fenestrated base of the long, large, and conical pecten, whose pointed
end reaches almost to the lens. There are no signs of choroidal
blood-vessels.

122

RATITjE

Casuariiformes

Plate III

Casuarius occipitalis

Apterygiformes

Plate IV

Apt cry. r mantelli

RATIT.E

Tinamiformes

Martineta Tinamou. Calodroma elegans. Plate V.

The background coloration is, in the main, a deep gray, the lower
half merging into dull orange. The whole of the fundi is covered by
a collection of tiny dots packed closely together. In the upper half
of the field they are white, but from the region of the disc and down-
wards they become a dull orange colour. Crossing the fundus and
running vertically on either side of the papilla are several orange-red
choroidal vessels.

The macula appears as a dull-gray area, with a brilliant white
central spot surrounded by a small, and a pale-green, streaked,
reflex ring. It is plainly visible on the nasal side of the pecten.
The optic nerve is oval in shape and exceptionally broad.

The mass of the pecten almost completely covers the optic
papilla, which is quite white and looks like a mass of coarse opaque
nerve fibres. The optic margins are bordered with gray pigment,
from which spring a few short opaque nerve fibres. The pecten is
chocolate brown, and in addition to its massive appearance is much
shorter than the same organ in most of the birds examined. It is
easy to see that it is fringed all round with pointed tabs, that the
central portion or ridge is serrated and that it comes well forward
towards the lens.

CARINATiE
Galliformes
Yarrell Curassow. Crax globosa. Plate VI.

The eyeground is a dull, leaden gray, covered with tiny, white
dots. There are no visible choroidal vessels.

The papilla appears as a long oval, whose central zone is dull
orange mingled with minute, dark-brown dots. It also presents a
marginal fringe of white. A few opaque nerve fibres extend on either
side of the disc across the fundus, but for a short distance only.

The pecten, of spiral form, is colored dark chocolate-brown. It
seems to taper quite decidedly where it joins the disc, and looks
like the roots of a tree at its distal end, where the rootlets bury them-
selves in the disc. Just above the disc, some little distance to the
nasal side of the pecten, is a round, grey, softly outlined area near
which is seen a well marked reflex of a pale blue-green tone.

124

RATITjE

Tinamiformes

Plate V

Calodroma elegans

CARINATjE

Galliformes

Plate VI

Crax globosa

CARINATjE

Galliformes

Brush Turkey. Catheturus lathami. Plate VII.

The eyeground is dull, slaty gray, underlying numbers of fine,
light-gray dots. These dots are uniformly scattered over the fundus
except towards the nasal side. Here, on a level with the superior
end of the optic nerve and in the direction of the macular area, they
are of a more brilliant white, are closely packed together, and are
devoid of a reflex-ring.

Extending from either side of the optic disc and running at right
angles to that organ are a few, rather fine, semitranslucent nerve
fibres, which are lost towards the periphery.

The optic disc, whose upper end is shaped like the sharp bow of
a boat, appears to be composed of a mass of brilliant, white, opaque
nerve fibres.

The pecten, of the usual chocolate brown color, is massive and
somewhat club-shaped. It extends well forward towards the lens
and tapers rapidly as it approaches the superior end of the nerve.

Harlequin Quail. Coturnix histrionica. Plate VIII.

The ocular background is light gray sprinkled with minute
granules, which give it the appearance of a rough surface.

The optic nerve head gives one the visual impression that it is
formed of brilliant, white, short, coarse, opaque fibres. Its shape is
unusual, being long and narrow, with a rather striking resemblance
to the projecting, serrated jaws of the Sword Fish. Extending along
each side of the optic disc, at right angles to it, are a few rather pale,
thin, opaque nerve fibres.

The pecten is lighter brown in color than usual, and is very narrow
at its junction with the papilla. On either side of it are a few minute
dots of brown pigment. The inferior segment of the pecten forms a
corrugated, bulky mass which, however, extends well forward into
the vitreous cavity to the posterior surface of the lens.

[126]

CARINATJE

Galliformes

Plate VII

Culheiiinis hifliami

Galliformes

Plate VIII Coin mix histrionica

CARINATjE

Columbiformes

Wonga Wonga Dove. Leucosarcia picatct. Plate IX.

The ocular background is of a uniformly gray tint. White dots,
lighting up the fundus, are scattered over the entire field. A few
choroidal vessels are to be seen.

The optic disc forms a long oval; it appears as if it were com-
posed of a collection of white fibres, and these seem bunched together
for about one-half the length of the pecten. Opaque nerve fibres
radiate from the circumference of the papilla, while several orange-
red (choroidal) capillaries, interspersed with pigment dots, run on
either side of it.

The pecten appears as an exceptionally long, corrugated, dark-
brown mass. Seen through the mirror from above it has the appear-
ance of a piece of tarred rope. The single macular area is seen to the
inner side of the disc and a little above its upper end. The sheen of
the pale green reflex that plays about it when illuminated by the
light of the ophthalmoscope looks like watered silk. The fovea has
the appearance of a small green flare, something like that from a
bull's eye lantern seen close at hand.

European Wood Pigeon. Columba palumbus. Plate X.

The tint of the ocular background is pale slate-gray. The eye-
ground is covered with very small, dull-white dots, so that the whole
fundus presents a lighter shade of gray than it otherwise would. On
the lower half and each side of the optic disc are seen several orange
colored choroidal vessels, which become more numerous as one
approaches the periphery. Extending at right angles to the papil-
lary margin are a few opaque nerve fibres.

A little above the superior end of the optic nerve head and
towards the nasal side, is a small, round, apparently somewhat de-
pressed macular area of a dull-gray tone. From its margins run
a double row of fine, blue-green, translucent lines which form about it
a broken or irregular reflex ring. The bird becomes unusually rest-
less when the light from the ophthalmoscopic mirror is focused on
this part of the fundus. The optic disc appears of a dead white
color, and seems to have a fringe of short fibres of the same color all
about its edges. At the junction of the pecten with the nerve-head,
i. e., along the central area of the latter, one sees numerous brown
pigment dots that appear like small rootlets or capillaries and give
a reticulate appearance to the papilla.

The pecten itself has a dark chocolate-brown color and a cork-
screw contour; it is unusually long and narrow, and its lower seg-
ment appears to come well forward towards the lens.

128

CARINATjE

Columbiformes

Plate IX

Leucosarda picata

Columbiformes

Plate X

Columba palumbus

CARINAT.E

Columbiformes

Victoria Crowned Pigeon. Goura victoria. Plate XI.

This fundus oculi is of the gray color, seen generally in pigeons
and doves, and covered with minute white dots. On the upper and
nasal side of the fundus is the macula, a small dull-gray area sur-
rounded by a gray and green reflex of small lines. The optic disc is
long, narrow, boat-shaped and somewhat rounded at the upper end.
It looks as it were rather hollow and gray in the centre with a white
rim all around. A network of small, brown, pigment dots is dis-
posed along the centre on either side of the pecten; and some opaque
nerve fibres extend across the fundus on all sides of the nerve.

The pecten is of the usual dark chocolate tint. It is corkscrew-
like in appearance, but one end is rather club-shaped and looks as
if it were covered with small brown nodules. This segment conies
more prominently forward towards the lens.

Ralliformes
Crested Coot. Fulica cristata. Plate XII.

The predominant color of the eyeground is dull gray, every-
where sprinkled with minute, white dots that are more clearly seen
above the superior termination of the optic nerve and to the nasal
side of the pecten.

130

CARINAT^E

Columbiformes

Plate XI

Goura victoria

Ralliformes

Plate XII

Fulica cristata

CARINATjE

Ralliformes

Ipecaha Rail. Aramides ipecaha. Plate XIII.

The eyeground is a very pale uniform gray stippled with darker
gray and white dots, thus giving the whole field a granular appear-
ance. The horizontally oval macular area (on the nasal aspect
near the upper end of the disc) assumes a pinkish tone. At its centre
is a small pit with a brilliant, white central dot. Around the macular
region is a pale, blue-gray reflex which loses itself in the general tone
of the fundus, but appears quite sharp on the inner side of the oval
macular region. The disc is a narrow, white oval, whose length is
about one-third the height of the pecten. A number of opaque
nerve fibres run across the background at right angles to the papilla
and fade into the general gray of the fundus. The pecten arises
from the upper part of the disc, spreads out on it like the root of a
tree and gradually disappears into the papillary substance. From
this root a long, slender, spiral form projects into the vitreous. It is
brown in color, is of uniform width, looks like a corkscrew and
extends forwards and outwards as far as the eye can see, looking as
if it were pressed against the lower part of the lens. The anterior
end of the pecten is much darker in color than its posterior half.

Sphenisciformes
Black-footed (Cape) Penguin. Spheniscus dcmersus. Plate XIV.

The dominant color of the fundus is bright red shading to crim-
son. It is stippled with minute, dark-red and orange dots, much like
grains of sand. About a disc-length from the upper end of the optic
disc these dots become grayish-white; indeed, the fundal coloration
is distinctly gray towards the upper half of the eyeground. In a
region the same distance towards the temporal aspect of the back-
ground may be seen a cluster of pinpoint, brilliant, white dots in the
macular area. Penguins use the nictating membrane very fre-
quently when light is thrown on this part of the eyeground. The
optic disc exhibits enamel-white edges; it is hollowed out in the
centre, like a sewing-machine shuttle. Running across this con-
cavity and at right angles to the margin of the disc one sees a large
number of gray fibres.

The pecten lies along the centre of the nerve, where it is orange-
red in color and mottled with minute, brown pigment dots. The
pecten has the usual dark chocolate-brown shade. It is of spiral
form, like a corkscrew laid on its side. A few slender opaque nerve
fibres are visible on each side of and at right angles to the disc.

13^>

CARINATjE

Ralliformes

Plate XIII

A ra m ides ipecah a

Sphenisciformes

Plate XIV Spkeniscus demersus

CARINATjE

Alciformes

Puffin. Fratercula arctica. Plate XV.

The eyeground is red and rather uniformly stippled with small,
mixed light-red and dark-gray dots. Above the upper end of the
optie disc and towards the temporal side is a small, round, red area
surrounded by a pale, light -gray film, shot with bright lines on the
outer and inner margins — doubtless the macular region with its
central fovea. Head noticed that not only this area but most of the
upper half of the fundus is very sensitive to light. The optic papilla,
oblong, narrow and with a rounded upper extremity, lies low down in
the eyeground, while the pecten extends well forward and behind the
lower margin of the pupil. A view of the nervehead is much ob-
scured by the body of the massive pecten which almost covers it when
seen, as with the mirror, from above downward. The small seg-
ment visible with the ophthalmoscope appears not brilliant white
but rather a bluish-white, the margins of the pecten being covered
with black pigment.

Extending at right angles to the disc on both sides are a few very
fine, gray opaque nerve fibres that finally disappear in the fundal
periphery. The pecten is of the usual chocolate-brown color and
comes well forward towards the lens, especially in its inferior aspect.

Lariformes

Great Black-backed Gull. Larus mart nits. Plate XVI.

The general coloration of the eyeground varies from a dull gray
to a dull brown — mostly the latter — traversing which are many
reddish choroidal vessels running more or less in a vertical direction.
It is the number and visibility of these capillaries that give the red
tone to an eye-ground essentially gray.

The optic disc is a long, narrow oval, quite white, with a quan-
tity of fine gray lines radiating in all directions from the papillary
margin. On the inner aspect of the eyeground the macula is seen.
It is situated about one disc-length from the upper extremity of the
pecten and half a disc-length above the end of the same organ
on the inner side. The macula resembles a blue-green flake of iri-
descent glass. It is of oval shape with a reddish-brown center,
which, however, is unprovided with a reflex ring.

The pecten appears to be in folds; the lower, or broader portion
extends well forward towards the lens and turns towards the nasal
side of the bird's head. The inner quadrants of the fundus are more
easily seen with the ophthalmoscope than the outer half but, so far as
the latter area is visible, there is no sign of a second macula on the
outer part of the eyeground.

134

CARINATiE

Alciformes

Plate X\

F rat ere ul a arctica

Lariformes

Plate XVI

Larus marinus

CARINATjE
Charadriiformes

Stone Plover. (Edicnemus scolopax. Plate XVII.

The eyeground is reddish-brown, rather deeply pigmented near
the periphery and covered with orange-red dots that are very densely
packed on the upper half of the fundus. Below the optic entrance
are numerous choroidal vessels running parallel with and on either
side of the papilla. The macula is not clearly defined. It is situated
above the superior end of the disc on its inner or nasal side, and
about half the apparent length of the pecten from the upper end.

The fundus coloring is slightly darker in the macular area, which
is surrounded by a reflex ring, pale gray in color, in the form of
very minute lines radiating from its margins. There are. also, a few
radiations near the fovea centralis. The papilla is white, oval in
shape, fringed all round with dense black pigment, and a few gray,
opaque nerve fibres are seen on either side of it. The pecten is very
large and projects well into the vitreous. It is of unusual shape,
rather narrow, but when examined from above looks as if it had been
compressed and flattened on both sides, with a narrow edge above.

Gruiformes
Ivvor. Rhinochetus jubatus. Plate XVIII.

The background is covered with a mass of minute dots that are
gray in the upper half of the fundus and orange below. The lower
sectors of the fundus are stippled with pigment. Choroidal vessels
are numerous and run in rather straight, vertical lines on both sides
of the optic disc. They are dull orange in color. The fovea is
shown towards the anterior or nasal half of the retina, and appears
as a round hole or crater-like depression, brown in color, which re-
flects a grayish sheen from its centre. A narrow gray circle or reflex
ring surrounds this pit.

The optic disc has its central portion apparently stippled with
bright orange-red dots, while its margin is fringed with coarse, white
fibres, that are also studded with brown pigment dots, especially near
the outer border.

The pecten is of the usual, deep chocolate-brown color, rather
narrow where it joins the disc but becoming much thicker and more
massive as it projects into the vitreous towards the lens.

l.'ifi

CARINATvE

Charadriiformes Plate XVII (Edicnemus scolopax

Gruiformes

Plate XVIII

Rhinochetus jubatus

CARINATJE

Gruiformes

Brazilian Seriema. Cariarna cristata. Plate XIX.

The dominant color of the fundus oculi is a dull-drab. Over the
lower quadrants of the eyeground run rather straight, dull-red,
choroidal capillaries that fade away as they reach the upper half
of the field. This region is also shot with a greenish-blue, muslin-like
film, which is probably a reflection by the retina of light rays from the
ophthalmoscopic mirror. Above the end of the disc is a small,
round depression, quite clear of any reflex. To the inner or beak
side of the eye is the circular macula, whose diameter is about three
times that of the cavity at the end of the disc. The centre of the
larger circle is quite clear, with the exception of a bright shimmer,
such as is sometimes seen about the human fovea. The circum-
ference of this circle is sharply defined, and has a bright ring around
it of glistening white. The optic disc appears as a long white oval,
with irregular margins. The black-brown corrugated pecten is
very large and long; it extends into the vitreous and almost touches
the lens with its club-shaped terminal. Very fine opaque nerve
fibres radiate at regular intervals from the whole papillary circum-
ference.

Ardeiformes
European Night Heron. Nycticorax nycticorax. Plate XX.

The eyeground is dull gray and covered with grayish-white dots.
The lower part of the fundus exhibits a number of dull-red choroidal
vessels, that run in a vertical direction.

The optic disc is long and of medium width, with both extremities
rounded. Its centre is orange-red and covered with minute, brown
pigment dots. The pecten is deep brown and its outlines are well
defined the whole length of the papilla. Linear, grayish radiations
extend from the upper two-thirds of the optic entrance.

The macula is situated quite close to and towards the upper-
nasal aspect of the disc. It is surrounded by an outer ring of whitish
lines, towards whose centre is a zone that closely resembles the sur-
rounding retina. In its exact centre, again, is a small fovea com-
posed of gray-white striae.

[ 138

CARINATjE

Gruiformes

Plate XIX

Carl a nut cristata

Ardeiformes

Plate XX

Nycticorax nycticorax

CARINATjE

Ardeiformes

European Bittern. Botaurus stellaris. Plate XXI.

The eyeground, mostly mouse-colored shading to yellow, is
sprinkled with small, dull-white dots. Almost immediately above
the upper end of the optic nerve entrance and towards the nasal
side of the disc is the macular area. The fundal dots at this point
are much duller in tone and incline towards a dull buff color. The
region of the macula, enclosed by two circles, one within the other,
is also characterized by the presence of very short, bright, bluish-
green lines radiating from the centre of the fovea.

The optic disc is ovoid, blunt at its upper extremity, and appears
as if its longer margins describe a series of small curves correspond-
ing to the folds of the pecten. The disc on either side of the root of
the pecten is dull-brown; near by are small, orange-red choroidal
capillaries. The papillary margins are quite white and, in contrast
with the shadow cast upon the neighboring field by the dark pecten,
the disc stands out in sharp contour. Extending a short distance
over the fundi and about the optic disc are a few opaque nerve fibres.
The pecten, convoluted, with serrated margins, and of the usual
chocolate-brown color, extends below the lower end of the optic disc.

Boat-billed Night Heron. Cancroma cochlearia. Plate XXII.

The eyeground is dull-red and covered with orange-red dots.
These punctate deposits are intermixed on the upper half of the
fundus with smaller and brighter dots of a grayer tone. On the
lower half and on each side of the optic nerve are a few orange-red
choroidal vessels, that run in a vertical direction, parallel to the
long axis of the disc. The macula is situated towards the nasal side
of the nerve head. This sensitive area is rather brighter in color
than the surrounding field, and several white dots are included in it.
These small dots, however, are noticeable only when the light of the
mirror is reflected on the region in certain directions. Rather a
bright, irregular and linear reflex surrounds the macular region,
which is very sensitive to light. There is a long, narrow papilla with
rounded extremities. It appears as if it were composed of short,
white fibres, surrounding an orange-red centre covered with minute,
dark-brown pigment grains that form a network over the whole red
area. Extending from each side of the disc across the retina are a
few dull-gray, opaque nerve fibres.

The pecten can be traced the whole length of the disc; it is dark
brown in color and grooved spirally like a corkscrew. It does not
appear to come far forward towards the lens, and its union with the
nerve head can readily be traced.

140

CARINAT.E

Ardeiformes

Plate XXI

Botaurus stellar i.-

Ardeiformes

Plate XXII

( 'ancroma cochlearia

CARINATjE

Ardeiformes

Glossy Ibis. Plegadis faldnellus. Plate XXIII.

The general color of the eyeground is blue-gray. It is covered
by a mass of minute, grayish dots, that probably furnishes the light
but brilliant gray tone that appears when the rays reflected by the
ophthalmoscope are thrown on it. The inferior quadrants of the
fundus, including both margins of the optic disc, exhibit a large
number of orange-red choroidal capillaries. They are very numer-
ous below the nerve-head, and suffuse the whole fundus near the
periphery with an orange-pink glow.

Apparently there is but one macular area, situated above the disc
and on its nasal side. In the centre of this region is a small, white,
round dot, surrounded by a brilliant blue-green reflex. There are,
also, fine fibres radiating from the centre of the fovea.

The papilla seems to be formed of a mass of coarse, white fibres.
It can be traced for about half its length only, the lower part being-
obscured by the massive, club-shaped pecten. The hitter organ,
of the usual chocolate-brown color, projects well forward towards
the posterior aspect of the lens. The disc is bordered with black
pigment which resembles a shadow cast on the eyeground. A large
number of semi-translucent nerve fibres originate at the edges of
the optic nerve on all sides, extend across the choroidal vessels and
eventually disappear.

American Jabiru. Mycteria americana. Plate XXIV.

The general color of the fundus is a slate-gray, the whole eye-
ground being quite uniformly sprinkled with small, but variously
sized white dots. In the upper and nasal quadrant of the picture is
the small, single macula, an area darker than the surrounding parts,
whose exact centre is occupied by the fovea. In the lower two-thirds
of the field are seen numerous, plainly marked choroidal vessels that
extend the whole length of the pecten, converging somewhat towards
the posterior aspect of its base. About two-thirds of the long and
rather broad nerve-head is plainly visible, except the central portion,
which is partly obscured by the pecten. This large, black-brown
organ, divided into 15 large and several much smaller double folds,
terminates above in a thin, dark rod. The disc is fringed by dark
pigment grains and from its lateral margins project a number of
short, faint, whitish lines.

142

CARINATjE

Ardeiformes

Plate XXIII

Plcgadis falcinellus

Ardeiformes

Plate XXIV

Mycteria americana

CARINATjE

Ardeiformes

Spoonbill. Platalea leueorodia. Plate XXV.

The color of the eyeground is decidedly gray, becoming brownish
towards the periphery. The entire fundus is covered with minute,
irregularly shaped, gray-white dots, that appear more distinct about
the macular region. At the fovea, where they are brilliant white,
they are still more closely packed. The foveal region appears to be
sunken below its surroundings and to be enclosed in a pale, greenish
(reflex) ring that is of oval shape, with its long axis horizontal. The
optic disc is a long, narrow oval, and presents a brilliant white
appearance. Near its upper end are several choroidal vessels of a
pale, golden-yellow color. Parallel to the long axis of the nerve-
head is another elongated mass of white fibres (almost like a second
optic disc) having its centre stippled with fine pigment dots, and
extending across the eyeground. Radiating from the margins of
the papilla one sees a number of faint, translucent fibres crossing
the small white area on the nasal side of the nerve.

The pecten does not extend very far forward; it is dark gray-
brown and appears to be completely covered with a number of warty
protuberances. It appears to be attached to the whole length of the
centre of the disc, that is stippled with fine red dots.

Anseriformes

Black-bellied Thee Duck. Dendrocygna autumnalis. Plate XXVI.

The eyeground is colored a light fawn besprinkled with minute,
white dots, that glisten when a strong light from the mirror is thrown
upon them. On each side of the papilla is seen a number of choroidal
vessels, bright orange in color and rather straight. The disc is also
orange-red along its major axis, this central zone being stippled all
over with a network of fine black dots. The circumference of the
disc is fringed with white fibres. The dark-brown pecten arises, as
usual, from the whole length of the disc. Mewed from above it
seems very thin and twisted like a corkscrew. A few opaque nerve
fibres extend for a short distance and at right angles to the disc on
either side. The upper part of the fundus is almost obscured by
numerous minute, brilliant, white dots.

144

CARINATiE

Ardeiformes

Plate XXV

Platalea leucorodia

Anseriformes

Plate XXVI Dendrocygna autumnalis

CARINATjE

Anseriformes

Blue Snow-Goose. Chen ccerulescens. Plate XXYII.

The fundal color is a distinct fawn, sprinkled with small, round,
orange-pink dots of irregular shape and size. Running vertically
past and parallel with the optic papilla, over the lower half of the
fundus are numerous, straight orange-red choroidal capillaries.

The fovea is probably indicated by a small, glistening white dot
above the end of the disc on the nasal side.

The optic nerve head is boat-shaped, tinted orange along its
central zone, and shows a narrow rim of coarse opaque nerve fibres
that form a fringe about its circumference. This orange centre is
sprinkled with numerous minute, dark-brown or black dots. A
few gray opaque nerve fibres arise from the disc margins and cross
the fundus horizontally. The pecten, of corkscrew shape, runs the
whole length of the disc and comes well into the vitreous.

Pelecaniformes
Cormorant. Phalacrocorax carbo. Plate XXVIII.

The fundus oculi is mostly of a slate-gray color, uniformly
sprinkled with numerous, minute white dots, closely packed together.
Running chiefly parallel with the long axis of the optic disc are
several rather straight, orange-red choroidal capillaries, that extend
the whole length of the papilla and beyond its inferior extremity.

The macular area is seen a little above the upper end of the
optic disc and on the nasal side of the nerve. The fovea appears
as a reflex image of a few short, bright, white lines surrounded by a
narrow ring.

The optic disc appears as if it were composed of a mass of very
white, cotton-like fibres, disposed as a fringe all about the papillary
margin. The central area of the disc, especially on each side of
the root of the pecten is orange-red, stippled with minute, brown
pigment grains. Perpendicular to the papillary margins are a few
short, fine opaque nerve fibres, that run towards and are finally lost
in the peripheral eyeground.

The pecten is rather long and of the usual chocolate color; it is
much narrower than usual on the upper half of the disc, and comes
well forward into the vitreous humor, extending behind the margin
of the pupil.

146

CARINATiE

Anseriformes

Plate XXVII

Chen ccerulescens

Pelecaniformes

Plate XXVIII Phcdacrocorax carbo

CARINATJE

Pelecaniformes

Gannet. Sula bassana. Plate XXIX.

The general color of the eyeground is dull yellow with a gray
tint, everywhere covered with light gray dots, that are most numer-
ous on the upper half of the fundus. Below, and on each side of
the optic nerve, are several orange-red choroidal vessels, that are
fairly straight and run parallel with the long axis of the disc.

The nerve entrance and pecten are situated rather high up in
the field; consequently it is easy to examine the details of the peri-
papillary background.

Above the upper end of the optic disc and a little towards the
nasal side, is a small circular macular area, red in tone but surrounded
by a larger circle, like a gray shadow. The margins of the latter
gradually fade into the background. The visible margins of the
papilla, apparently composed of coarse, white, opaque fibres, are
not, as in many species, covered by the pecten. The central part,
near the root of the pecten, is orange-red in color.

The pecten itself is evidently attached to the disc for nearly its
entire length, and it does not come forward towards the lens.

Australian Pelican. Pelecanux conspicillatus. Plate XXX.

The color of the eyeground is a dull but deep gray, sprinkled
generally with irregular dots that are most numerous in the upper
part of the fundus. The lower quadrants of the field are covered with
a rather faint orange-red, choroidal capillary system, disposed in a
vertical direction. The disc is a wide, pointed oval, exhibiting a
number of bright-red orange ridges that are uniformly stippled with
black pigment dots. The disc margins stand out as a clear white.
The pecten, broad and massive, seems to fill the pupillary area. It
projects far into the vitreous, reaching, indeed, the posterior surface
of the lens. In spite of its large size and intraocular disposition both
the free and the attached ends of the pecten can be outlined by the
ophthalmoscope. Passing in a radical direction from its circum-
ference is a number of opaque nerve fibres.

The single macula is to be found on the inner side of the fundus.
It is surrounded by a narrow, sharply defined, reflex ring of greenish
color.

148

CARINATjE

Pelecaniformes

Plate XXIX

Sulci bassana

Pelecaniformes

Plate XXX Pelecanus conspicillatus

CARINATiE

Serpentariiformes

Secretary Bird. Gypogeranus vel Serpentarius serpentarius.

Plate XXXI.

The general color of the eyeground is dull gray, pitted with mixed
light and dark brown pigment grains or dots, the darker being about
double the size of the lighter granules. Mixed with these dots is a
dense mass of minute, bright points that cover the whole fundus, but
they can be observed only when the reflected light of the mirror is
thrown on them. These deposits give the background the appear-
ance of a rough surface. A thin layer of translucent nerve fibres
surrounds the papilla for a short distance, particularly along the long
axis of the nerve-head.

A little above the upper end of the optic disc and towards the
nasal side is the fovea centralis, a round white dot enclosed by a
narrow ring of bright green. On the temporal side of the disc, and
above the end of it. is also a long, narrow, sensitive area. This
part is enclosed by a shimmering reflex of green light.

The optic disc is long and rather narrow, both ends being rounded
off. It is quite white and deeply pigmented at its outer and upper
borders.

The pecten is of a lighter brown than usual, is plainly serrated
on either side and appears as a narrow band that extends the whole
length of the disc. Just before its junction with the optic nerve-
head it is stippled with bright, orange-red grains. The central part
of the pecten does not project far forward into the vitreous; it ap-
pears to be quite narrow while the whole length of its upper edge or
crest seems rather wavy.

Accipitriformes
Lammergeier. Bearded Vulture. Gypaetusbarbatus. Plate XXXII.

The eyeground is slate-gray and presents everywhere a granular
appearance. The lower half of the fundus is covered with dull
orange-red choroidal vessels that run in a vertical direction, parallel
to the sides of the optic disc.

Above the papilla (about two disc breadths from it on the nasal
side) is a small, round, dark-brown pigmented pit, surrounded by
two distinctly marked, brilliant reflex rings, each having a greenish
tint. On the nasal side of the nerve-head, but nearer the latter and
much less distinctly outlined than the depression just described, is
the second macular region with its fovea. It has a soft, indistinct
but dark centre. The optic entrance is pure white with an orange-
red central area from which arises the pecten. This body is very
narrow and tapers on its upper aspect for about one-fifth of its length.
It then becomes much broader and almost covers the outer zone of
the disc.

I.iO

CARINATjE

Serpentariiformes Plate XXXI Gypogeranus vol Serpentarius serpentarius

Accipitriformes Plate XXXII Gypaetus barbatus

CARINATuE
Accipitriformes

Bald Eagle. Haliaetus leucocephalus. Plate XXXIII.

The fundus is mostly a dark reddish-brown, the lower half chang-
ing to a dull orange-red. The lower eyeground is covered with
choroidal vessels, and is dotted with brown pigment grains, giving
it a rough, granular appearance. A gray sheen pervades the upper
part of the fundus. On the temporal side and some distance from
the upper end of the optic nerve is a brilliant, white, round dot sur-
rounded by a small, light-green reflex ring, which is itself enclosed in
a brilliant, narrow, green macular region. On the nasal side of the
disc, and on a level with this macula is another area, of a gray color,
surrounded by a fan-shaped, luminous reflex.

The optic nerve entrance is distinctly white, and along its centre
is strewn a large number of minute pigment dots. The outer margin
of the disk is bordered with black pigment, as if a shadow were cast
upon it by the pecten.

White-bellied Sea Eagle. Heliaetus leucogaster. Plate XXXIV.

The coloration of the eyeground is mostly dull-brown, the lower
quadrants of the field being covered with dull, orange-red, choroidal
blood-vessels. The disc is a long white oval, whose centre is tinted
with orange and covered with tiny pigment dots. The papillary
margins are white bordered with black pigment.

The upper half of the fundus is covered by a mass of dull gray
dots. There is a well defined reflex near both macula?.

The pecten is very large and comes well forward towards the
posterior surface of the lens. Both extremities of the organ are
clearly visible through the ophthalmoscope. There are very opaque
nerve fibres to be seen in any part of the eyeground.

152

CARINATvE

Accipitriformes Plate XXXIII Haliaetus leucocepkalus

Accipitriformes Plate XXXIV Heliaetus leucogaster

CARINATjE

Accipitriformes

European Kestrel. Tinnunculus alaudarius. Plate XXXV.

The principal coloration of the fundus is a light brown, or brown-
ish-gray. The lower quadrants are streaked with orange-red,
choroidal capillaries that run in a more or less vertical direction,
and become more distinct and brighter red as they approach the
periphery of the field. The optic disc is a long, white oval, showing-
its margins well beyond the pigmented and fringed pecten. The
central area of the papilla appears to be hollowed out like a canoe
and the pecten does not overlap it at any point of its circumference,
as is so frequently the case in avian fundi.

The disc extends as far downwards towards the fundal periphery
as the observer's eye can reach. At its lower extremity several small
choroidal capillaries can be seen.

The pecten has a rounded, pyramidal form, sloping towards the
centre of the disc at both ends. It is of a dull brown color, and
corrugated like a photographic camera. At the junction of pecten
and papilla are scattered numerous brown dots, so disposed as
to give the former the appearance of a web. The upper part of the
eyeground is quite devoid of choroidal vessels, but is covered with
minute white dots. The fundus is much clearer of tin- retinal shimmer
or reflex noticed in most birds. The two macular regions are distinctly
visible. The nasal macula is situated just above the upper end of the
disc and about half a disc-length on the inner or beak side of the eye-
ground. It is a dark-brown spot with a pale area all around it. ( hit -
side of this region and enclosing it are two distinct, pale green filiform
reflex rings, the interior rings being quite free from the white dots.
On the outer aspect of the eyeground, about one-third the length of
the disc above and two-thirds to the outer side of the disc, is the tem-
poral macular region. At its centre is a light, gray spot surrounded
by a dark brown area. Both these area? are in their turn encircled by
a small, pale-green, reflex ring about one-fourth the diameter of the
corresponding circle about the superior macula. Slender, opaque
nerve fibres run out at right angles to the disc on both sides.

Little Bustard. Tetrax tetrax. Plate XXXVI.

The fundal coloration is mostly a warm gray, covered with small,
dull orange-red dots. In the lower half of the field and on each side
of the optic nerve entrance is a number of choroidal vessels of a dull
orange-red color, running parallel with the disc.

So far as seen the papilla is a dead white; optic fibres form a
fringe-like setting about it. The central zone of the disc is covered
by a mass of minute, brown, pigment deposits of irregular shape.
Opaque nerve fibres extend at right angles to the disc on either side.
A little to the temporal side, about one disc-length from the upper
end of the optic nerve, is a small, brown spot like a tiny hole. This
macular area is surrounded by a brilliant, green reflex ring. The
pecten, of a dark chocolate-brown color and shaped like a corkscrew,
comes well forward towards the inferior border of the lens.

[ 154 ]

CARINATjE

Accipitriformes Plate XXXV Tinnunculus alaudariui

Accipitriformes Plate XXXVI

Tetrax tetrax

CARINATjE

Strigiformes

Tawny Owl. Syrnium ahico. Plate XXXVII.

On the outer aspect of the papilla and about one disc-length from
it on a level with the upper margin of the pecten, is a slight depression
almost devoid of choroidal vessels. Its centre is a dark red color,
and on the margins of the depression and surrounding it is a bright
circular reflex. For some distance outside this fovea] ring the eye-
ground is seen as if one were viewing it through a translucent, grayish
mist or haze; and the fundus thus seen generally appears to be
granular with a few, small choroidal vessels showing here and there.
Inside the ring, however, the details are strikingly clear, and the
coloration bright red. Above the macula, on the outer side of the
disc, is a quantity of dark pigment deposited between the choroidal
vessels, by contrast making the latter stand out as of a bright orange
color. The inner aspect of the fundus appears yellow; it exhibits
numerous choroidal capillaries whose yellow tint is distinctly brighter
near the inferior segment of the disc.

--&1

Common Barn Owl. Strix flammed. Plate XXXVIII.

The general tone of the eyeground is dull gray, with bright orange-
red choroidal vessels distributed all over the fundus except at the
macular region. At this area the tint is much grayer, being, in
addition, stippled with small, irregular blotches of orange-red and
gray dots. The macula, also suffused with a deep gray reflex, is
situated above the upper end of the optic disc and nearly in a line
with the long axis of that organ.

The papilla is long and narrow with pointed ends, and appar-
ently made up of coarse white fibre-bundles the central portion of
which is covered with minute, brown, pigment grains, that have a
distinctly reticulated appearance. These white fibres border the
nerve head all around.

The dark-brown, convoluted pecten is large and extends well
forward towards the lens. From both sides of the disc radiate a
few, dull-gray fibres that stretch a short distance across the fundus
and then disappear.

1.56

CARINATjE

Strigiformes

Plate XXXVII

Syrnium aluco

Plate XXXVIII

Strix flammea

CARINATvE

Psittaciformes

Orange-winged Parrot. Chrysotis amazona. Plate XXXIX.

The general color of the eyeground is a deep gray, tinted with
buff. The lower sector and the peripheral zone are suffused with
pink, the background generally being punctuated with minute,
dull-yellow dots. The macular area is situated towards the nasal
side of the disc, a little above the end of the pecten. It is slightly
depressed and enclosed with a bright but pale green reflex-ring.
Extending from the circumference of this circle, slightly above as
well as below, are a few translucent fibres, pale green in tone; and at
its centre is a dark-gray dot or depression, with a small, faint halo
extending from its upper edge.

The optic nerve-head looks as if it were composed of coarse, white,
opaque fibres, which form a fringe all around the deeply-colored
pecten. The papilla is long and boat-shaped and its outlines can
be traced the whole length of the pecten. Many fine, gray, opaque
nerve fibres extend from the margin of the papilla, cross the back-
ground of the eye and are eventually lost in the fundal tissues.

The deep brown pecten, seen from above, has a spiral form, with
a tag or tail-piece at the upper end. A lateral view shows it to be
plicated, like a fan. It stands well forward towards the lens, espe-
cially its lower half. It has a dark brown color.

Kakapo. Owl-Parrot. Stringops habro'ptilus. Plate XL.

The eyeground is orange-red stippled all over with lighter orange
dots. The lower half of the fundus has a large number of minute
dark, reddish-gray depots of pigment intermingled with lighter dots;
also, a great many choroidal vessels run in a vertical direction over
the field of view on either side of the optic entrance. They become
more numerous towards its lower periphery.

The macula is placed, as in Owls generally, on the temporal side
of the optic papilla, about one disc-length from its upper end and
half that distance to the temporal or outer aspect of the fundus. It
is a bright orange-red area surrounded by dark, red-gray pigment,
like a shadow. There is no circular sheen around it, such as has
been noted about other avian fovese.

The optic nervehead is white, and along its centre appears a net-
work of minute, brown pigment dots clustering around the sides of
the pecten. A few white opaque nerve fibres extend a short distance
on either side and about the upper end of the disc.

The black-brown pecten extends the whole length of the disc.
It is rather straight in its upper half but is more convoluted towards
the lower part, where it is quite massive and resembles a corkscrew.
It comes well more forward towards the lens, so that it more nearly
resembles the same organ in the Burrowing Owl than in the Parrot.

158

CARINATiE

Psittaciformes

Plate XXXIX

( 'li rysot is- a mazona

Psittaciformes

Plate XL

Stringops h ab ropt ilus

CARINATiE

Psittaciformes

Great Sulphur-crested Cockatoo. Cacatua galerita.

Plate XLI

The background is of a fairly uniform, light, grayish-blue color,
sprinkled with minute white dots interspersed with many less numer-
ous but somewhat larger dark gray deposits. The macula, at the
upper-inner quadrant, is an irregularly round, light brownish area
whose diameter is half the disc length; and whose periphery fades
into the surrounding gray of the fundus. The upper sixth of the
long, pointed papilla is distinctly visible where it is not covered by
the indented pecten, whose twelve double folds have a corkscrew
termination above. Portions of the disc borders can be seen from
above through the plications, except at its posterior terminal, where
the dark-brown mass entirely covers it. Faint, whitish lines of
opaque nerve fibres extend from the margins of the upper half of
the disc a short distance across the centre of the eyeground.

Coraciiformes
Laughing Kingfisher. Dacdo gigas. Plate XLII.

The fundus oculi is in general of a light fawn-gray color mingled
with irregularly shaped white or gray-white dots, except in the
neighborhood of the optic nerve where it is orange-red, like the glow
cast on the sky by the setting sun. The optic nerve entrance is long
and narrow; it is white except along its central area, which is orange-
red striped with brown pigment dots. A large number of opaque
nerve fibres run out on each side of the optic nerve and at right angles
to it. The pecten is very long and narrow and has the appearance of
a brown centipede.

The macula is very conspicuous. About half a disc-length from
the upper end of the nerve, towards the nasal side, is a small, round,
dark depression, surrounded by a very narrow, bright green ring.
This circle encloses a smaller area that is of a darker gray and devoid
of the dots seen at other parts of the eyeground. The fovea nasalis
always appears directly opposite the pupil; there is no fovea tempo-
ralis visible to the ophthalmoscope.

160]

CARINATiE

Psittaciformes

Plate XLI

Cacatua galerita

Coraciiformes

Plate XLII

Dacelo gig as

CARINATjE

Coraciiformes

Black Hornbill. Spagolobus adratus. Plate XLIII.

The principal color of the eyeground is dull gray, interspersed for
some distance about the optic nerve entrance with a mass of fine
opaque fibres that extend about a disc-length over the fundus. Be-
yond the fibres are several dull-colored choroidal capillaries that cross
the fundal field in a vertical direction. Near the macular region the
fundus is illuminated by a brilliant gray iridescence.

The optic disc is a long, white oval, that extends downward and
a little inward towards the inner or beak side of the head. The
pecten is very large, the lower segment being carried far forward
behind the iris; it presents serrated margins.

The macular region is quite circular and is red-brown in color.
An inner circle is dead white, while the foveola is represented by a
dark-red central spot. There are two bright rings around the
macula of an iridescent, blue-green color, the fundus between the
two circlets being a light luminous gray.

European Nightjar. Caprimulgus europeus. Plate XLIV.

The eyeground appears orange-red, everywhere stippled with
small, red and brown patches of irregular shape. Scattered about
are several pigmented areas, such as one sees in the eyes of human
subjects with disseminated choroiditis. There are a few choroidal
vessels in the lower half of the fundus. These are faintly outlined,
but they give to that part of the eyeground a deeper red than the
remainder of the background.

The optic papilla is short and broad. The antero-posterior view
with the mirror shows it as a dull, grayish-white body largely covered
with brown pigment dots. Its margins, where it is not obscured
by the mass of the pecten, is much lighter in color. Radiating from
the sides of the disc, and extending for a short distance on either
side, are a few white, opaque nerve fibres, which are light gray and
become less distinct on the outer side of the papilla.

162

CARINATjE

Coraciiformes

Plate XLIII Spagolobus adratus

Coraciiformes

Plate XLIV Caprimulgus europc

CARINATiE

Cuculiformes

European Cuckoo. Cuculus canorus. Plate XLV.

The eyeground is gray with a suggestion of fawn, everywhere
besprinkled with grayish-white dots. Towards the lower quadrants
of the fundus, in particular at the extremity of the pecten, the back-
ground is suffused with a dull pink. Near the optic nerve on either
side are several, plainly visible, orange-red choroidal vessels.

The macula is seen above the disc towards the nasal side. This
area, slightly red in tone, appears depressed below the fundal surface,
although no definite fovea is visible with the mirror.

The papilla is almost completely covered by the pecten so that
only the outlines of the former can be seen by the anterior-posterior
inspection of the ophthalmoscope. Where the papillary margin is
visible it shows extremely white.

The pecten also extends well above and below the disc terminals
and projects deeply into the vitreous chamber. It appears by the
mirror to be a chocolate-brown color. Opaque nerve-fibre radiations
are seen to originate at the disc margins, whence they cross the back-
ground and finally disappear from view at or near the fundal
periphery.

Piciformes
Sulphur-breasted Toucan. Rhamphastus Icematus. Plate XL VI.

The eyeground is dull gray in color, rather regularly spotted
with whitish-gray dots. The optic papilla is apparently composed
of short, coarse, white fibres which form a sort of fringe all round its
margins. Along each of its sides and parallel to its long diameter a
few orange-red, choroidal vessels are seen. Radiating from the
papillary circumference are numerous opaque nerve fibres that
extend to the fundal periphery across the eyeground on all sides.
The pecten is almost black-brown in color.

Above the end of the optic nerve entrance and about half its
length to the nasal side are three dark-brown spots, clustered together
and surrounded by a small gray reflex.

164

CARINATiE

Cuculiformes

Plate XLV

Cuculus canorus

Piciformes

Plate XLVI Rhamphastus loematus

CARINATvE

Piciformes

Gila Woodpecker. Centurus uropygialis. Plate XLVII.

The fundus oculi is dull gray tinted with yellow and nearly uni-
formly charged with minute, gray dots. At the superior termination
of the optic disc (on the nasal side) is a small gray depression, partly
surrounding a central, well-marked and glistening white dot. Within
this area are also several golden yellow dots.

The outlines of the optic nerve entrance are well defined, and
the central area of the papilla at its union with the pecten is dull
orange stippled with dark brown pigment. The papilla is fringed
with coarse white fibres. A large number of translucent nerve fibres
radiate from the edge of the optic disc on all sides; they become
fainter and fainter as they approach the fundal periphery and
finally disappear.

The pecten, of the usual chocolate brown color, reveals several
corkscrew convolutions. It comes well forward towards the lens,
and presents a massive, club-shaped appearance.

Greater Spotted Woodpecker. Dryobates vel Dendrocopus major.

Plate XL VIII.

The color of the eyeground is a dull but definite gray, interspersed
with a large number of small, gray dots. Below the optic disc and
pecten are a few faint, orange-red choroidal vessels. The optic disc
is apparently made up of a mass of brilliant, white, nerve fibres,
very short and thick. In the form of radiations from the margins
of the papilla towards the fundal periphery are many gray opaque
nerve fibres that appear to occupy a plane lower than the white ele-
ments of the disc. The pecten has three corkscrew convolutions on
the disc, while its lower part forms a club-shaped mass of a dee])
chocolate-brown color that appears to come well forward towards the
lens.

There seems to be only one sensitive central area. This single
macula is on the nasal side of the pecten and has the appearance of a
brilliant, white, round dot, the fundus surrounding it being a little
darker than the general color of the eyeground. The surrounding
gray area makes the white fovea stand well forward almost as if it
were actually situated in the vitreous. No reflex ring can be seen
around it.

166

CARINATjE

Piciformes

Plate XL VII Centurus uropygialis

Piciformes Plate XLVIII Dryobates vel Dendrocopus major

CARINATjE

Passeriformes. A. Mesomyodi. Tyrannidoe.

Derby Tyrant. Pitangus derbianus. Plate XLIX.

The eyeground is blue-gray, everywhere sprinkled with minute,
gray dots. These dots are so closely packed on the upper half of the
fundus that they give it a distinct silvery appearance. Running
at right angles to either side of the optic papilla are numerous dull-
white opaque nerve fibres; they extend well across the eyeground.
At right angles to the optic disc towards the nasal side and a little
above its superior end is a dense, pale-blue, punctate mass that
appears to surround the fovea. A light blue reflex ring also
encircles this area.

The optic nerve-entrance is long, narrow and white. Its centre
is stippled with a few brown pigment dots and it is bordered all
around with symmetrically placed black pigment granules. This
pigmented margin varies a little in individuals. The black-brown
pecten, long and narrow, extends well behind the edge of the pupil
so that a portion of it cannot be seen through the mirror. The upper
part is serrated but the lower half is more of the corkscrew type.

Passeriformes. B. Acryomodi. UinuuUnidw.
European Chimney Swallow. Hirundo rustica. Plate L.

The general color of the eyeground is warm gray, tinted slightly
with yellow or buff, and covered with minute, dull, yellowish dots.
Several pale orange (choroidal) vessels are seen near the upper ex-
tremity of the optic nerve-entrance. There are visible two macular
regions, one on each side of and above the upper end of the disc.
They show as small brown areas or dots in the eyeground. Sur-
rounding the temporal macula is a slight reflex, apparently com-
posed of minute, bright gray dots. The macula on the nasal side
is quite devoid of this reflex-ring.

The optic papilla, long and narrow, tapers at its upper end. On
either side of the disc, and at right angles to it are a few, fine, dull-
gray opaque nerve-fibres.

The chocolate-brown, convoluted pecten is quite narrow at its
junction with the optic nerve, but it gradually becomes wider and
more massive as it approaches the lens.

168

CARINAT.E

Passeriformes

Plate XLIX

Pitangus derbian us

Passeriformes

Plate L

Hirundo rustica

CARINATjE

Passeriformes. B. Turdidw.

Bluebird. Sialia sialis. Plate LI.

The general blue-gray coloring of the eyeground is modified by
numerous, pin-point dots. The punctate deposits near the periphery
assume a more or less dull-golden or orange tint, a condition also
noticed just below the peeten. The elongated, ovoid optic disc is
white (quite woolly at its margins) and covered almost entirely with
the convoluted peeten, which is very large when compared with the
size of the eye. It is of the usual dull-brown color and has "frilled"
borders. On the inner or nasal side and near the lower part of the
optic disc is an orange-red area, containing chiefly choroidal vessels
with black pigment grains between them. This red area extends
a little to the temporal side of the disc, subsequently merging into
the dull orange color below. On either side of the disc and radiating
from it, are numerous filiform nerve fibres which cross the background
almost to its periphery. In an area a disc-length to the nasal side
of the papilla the white dots of the fundus are decidedly fainter and
much closer together than elsewhere; in this region, also, there is a
reflex plainly marked.

Wiieatear. Saxicola aenanthe. Plate LII.

The fundal coloration is pale gray, with a dense mass of grayish
white dots permeating the entire background. Slightly above the
upper termination of the optic nerve, and towards the nasal side of
the peeten, is a well-defined, round, whitish macular region, much
larger than the small spots that cover the whole of the surrounding,
duller eyeground. This white area is inclosed by a brilliant, bluish-
green circle, which appears more prominent and iridescent in nature
than is depicted in the drawing. The optic papilla is almost entirely
obscured by the peeten; it is long and narrow, with an irregular
outline.

On the nasal side of the nerve-head are a few short, orange-red,
choroidal vessels with a few dots of pigment like pepper grains
sprinkled between them. Extending from both margins of the optic
disc across the fundus to the periphery, are numerous fine, opaque
nerve fibres, the upper ones (on the nasal side) terminating at the
macular area.

The peeten, red-brown in color, long and narrow, appears to
be twisted on itself like a rope or a corkscrew. Its inferior end
extends beyond that part of the eyeground shown in the picture, but
it probably comes well forward towards the posterior surface of the
lens.

170

CARINATjE

Passeriformes

Plate LI

Sialia sialis

Passeriformes

Plate LII

Saxicola aenanthe

CARINATjE

Passeriformes. />'. Fringillidce.

House Sparrow. Passer domesticus. Plate LI 1 1.

The general color of the fundus is pale-gray covered with very
fine white dots, closely packed together at the macular area. They
form a lighter zone a little above the upper extremity of the pecten
and towards the nasal side of the disc. From the circumference of
the optic disc a large number of rather long, opaque nerve fibres
run in radial fashion towards the periphery of the fundus. The
papilla appears, when visible, to be composed of irregularly shaped,
brilliant white bundles; it can barely be outlined with the mirror
except at the upper (and narrow) end of the pecten. The pecten
has a deep red-brown color, and its free extremity is long, narrow
and of the corkscrew type. The lower segment of the organ extends
well forward towards the lens and, being large and massive, com-
pletely covers the pupil and makes it impossible to obtain a lateral
view.

Varied Bunting. Cyanospiza versicolor. Plate LIV.

The eyeground is dull gray shaded to buff and besprinkled with
very minute, grayish-white dots. These dots coalesce at the macula,
where they form a soft, round area bordered by a light reflex. The
single macular region and fovea are situated a little above the upper
end of the pecten and towards the nasal side of the optic nerve.
The pecten, very large and massive for the size of the eye, is of the
usual chocolate-brown colour; it is more or less club-shaped, and
extends well forward towards the lens. Where the pecten joins the
retina it is very irregular in shape. The pecten, whose outline is
quite irregular, covers the papilla entirely so that it appears to
spring directly from the retina without showing the white disc mar-
gin. From the sides of the apparent root of the pecten a few,
whitish, opaque nerve fibres cross the field of view.

172

CARINAT.E

Passeriformes

Plate LIII

Passer domesticus

Passeriformes

Plate LIV Cyanospiza versicolor

CARINATjE

Passeriformes. B. Paradiseidce.

Law Bird of Paradise. Parotia lawii. Plate LV.

The eyeground is yellowish-gray or khaki color, uniformly covered
with a dense mass of minute white dots, that are smaller and denser
at the macular region. A few dull-red choroidal capillaries are
visible on the lower part of the fundus near the periphery. The
optic nerve head, dull white, long and narrow, has a rounded upper
end. Its entire central area appears as if it were a mass of fine,
brown pigment dots. The pecten is exceptionally long, rather nar-
row, spirally arranged and extends beyond the range of vision
through the undilated pupil.

To the nasal side and a little above the end of the disc is the
macular region, a dull-brown crater-like depression bounded by a
white mass of (reflex) st nations. Opaque nerve fibres radiate from
both sides of the disc but finally disappear as they approach the
boundaries of the fundus.

B. Corvidce.
Blue Jay. Cyanocitta cristata. Plate LVI.

The general color of the eyeground is a slate-gray, with a pale-
yellow tint in the lower half of the eyeground. The entire Held is
besprinkled with irregularly shaped, light-gray dots, giving it the
appearance of a rough and rather coarse surface, especially near the
macular area where the dots are more closely packed in I he shape
of a bright, circular patch.

The optic nerve-head is quite white and of oblong shape. Several
orange-colored, choroidal capillaries are visible in this region, that is
covered with minute, brown, pigment dots, like black pepper grains.
Extending from each side of the optic disc is a large number of
opaque nerve fibres that extend across the fundal field.

The pecten, of the usual chocolate-brown color, is rather irregular
in shape at its superior extremity. From above downward it looks
like a ship's tarred cable, becoming larger as it approaches its union
with the papilla. The superior end appears to come well into the
vitreous cavity and to reach the lens.

[174

Passeriformes

Plate LV

Parotia lawii

Passeriformes

Plate LVI

Cyanocitta cristata

CARINATjE

Passeriformes. B. Corvidae.

Common British Blackbird. Turdus merula. Plate LVII.

The general tint of the eyeground is a slaty-gray with a uniform
sprinkling of tiny, white dots. There is no visible macular region,
hut the whole fundus is covered and its coloring greatly modified by
numerous linear opaque fibres that arise from the disc margins
throughout and run across the entire fundus to the extreme periphery.
A few, faint, yellow-red choroidal vessels are seen on either side of
and parallel to the moderately long and narrow papilla. The upper
two-thirds of the disc is about half covered by the club-shaped
pecten, which is composed of very few folds. The massive, chocolate-
colored, posterior end of the pecten entirely obscures the lower third
of the disc, while the upper half of the former has a light brown mar-
gin on its nasal aspect, and seems to be only in part attached to the
nerve-head beneath it.

Raven. Corvus corax. Plate LVIII.

The eyeground is a light fawn sprinkled with dots about three
shades darker than the ground color. Mixed with the dark dots are
a number of white ones, seen especially when a strong light is thrown
upon the fundus. About three disc-breadths from the upper end
of the disc on the inner side is a well marked, bright reflex of a green-
ish-blue tinge. It is irregularly oval in shape and seems to be com-
posed of a number of very fine fibres. In the centre of the reflex is
the macula, a small, dark, crater-like depression, brown in color.
The disc is chalky white, and gives one the impression that it is
composed of many opaque nerve fibres packed closely together.
From the disc margins there radiate a number of fine optic nerve
fibres that extend across the eyeground. In the lower part of the
fundus, associated with a number of orange-red dots, are a few orange-
red choroidal blood-vessels, several of the latter being distributed
along either side of the disc. The pecten is very thin and narrow
at the disc but assumes a club-shape as it approaches the lens, where
it is darker in color. It comes well forward and appears at times
to press against the posterior capsule of the lens.

170

CARINAT^E

Passeriformes

Plate LVII

Turdii.s mcritht

Passeriformes

Plate LVIII

Corvus corax

COLORED DRAWINGS OF THF FUNDUS OCULI OF

REPTILES.

REPTILIA

Turkish Gecko. Hemidactylus turcica.?. Plate LIX.

The orange-red fundus is uniformly dotted with dark spots,
while the circular papilla is completely obscured by the chocolate-
brown pecten, whose pointed free end projects a medium distance
into the vitreous. Clearly defined, white linear medullated nerve-
fibres radiate from the disc margins, giving the effect of a halo about
the central zone of the picture.

Horned Toad. Phrynosoma cornutum. Plate LX.

The general coloration of the eyeground is a dark slate, irregu-
larly strewn with minute, whitish dots of various sizes. There is
an ill-defined macular region. The pear-shaped, grayish papilla
has a white margin, from which short fibres of unequal length radiate
towards the periphery. A single central (?) artery seems to originate
from the nerve-head and with its six branches — two on one side of
the disc, four on the other — is supplied mostly to the lower half of
the field. A small branch anastomoses above with a twig that runs
from the periphery of the fundus.

[178

REPTILIA

Turkish Gecko

Plate LIX

Hem idactylus tureicus

Horned Toad

Plate LX

Phrynosoma cornutum

REPTILIA

Indian Cobra. Naia tripudians. Plato LXI.

The general coloration of the fundus oculi in this Snake is light
gray-blue, sparsely dotted with pigment of a similar but deeper color.
The whole background is regularly covered with opaque nerve
fibres. From the button-like optic disc arise three vessels, appar-
ently two arteries of small size and one larger vessel — probably a
vein. The centre of the papilla shows the remains or the undeveloped
tissues of a pecten.

180

REPTILIA

Indian Cobra

late LXI

Naia tripudiam

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