Light and electron microscopy of the presumed
elastic components of the trabeculae and
scleral spur of the human eye
Takeo Iwamoto*
The trabecular meshwork and scleral spur of two young human eyes were studied by light
and electron microscopy in Epon-embedded material. Anteroposterior sections showed, in
light microscopy, numerous dots stained dark purple with Weigert's elastic stain and greenish
with Giemsa in both regions. In tilted frontal sections, similarly stained, long, circularly
oriented fibers toere observed, indicating that they were longitudinal sections of the dots
observed in the anteroposterior section. This material appears to be the saine lohich has been
described as elastic tissues when observed by conventional methods. With alternate thin and
thick sections, the fine structure of the above material is described. It consists basically of a
peripheral cortex and a central core. The distribution of these structures in the trabecular
meshwork and scleral spur is described, and their nature discussed, and compared with elastic
tissues of the aorta of the guinea pig.
methods were identical to the clumps of
1,000 A-banded material seen in the homogeneous matrix by electron microscopy, and
that this banded material was not elastic
tissue but actually belonged to the collagen
class of connective tissue. Recently, however, Leeson and Speakman5 reported an
"amorphous, finely fibrillar material" present in large amounts in infants but rarely
in adults, which the authors considered
was possibly elastin. Shikano and Iwamoto7 also obesrved elastic fiberlike structures in a zone intermediate between the
trabeculae and the scleral spur of the
adult human eye. They were located
mostly in the peripheral, but also in the
central part of the collagen of individual
beams. Each of the structures appeared to
be amorphous at low magnification, and
their central area was often less dense than
the periphery. At higher magnification,
however, these structures appeared to be
finely granular, or vesiculated.
.he trabecular meshwork of the human
eye has been studied with the electron
microscope by several investigators,1'7 and
the concepts formed by light microscopy
have been confirmed and modified.
With respect to the elastic tissue in this
area, the electron microscope studies seem
to have aroused questions rather than confirmed the conventional concept. Garron
and Feeney1 considered that the "elastic"
fibers seen by conventional histologic
From the Department of Ophthalmology, College
of Physicians and Surgeons, Columbia University, New York, N. Y.
This investigation was supported by research
grants NB 00492 (C 10) and 1202 (C 7), and
training Grant 5 TI NB 5324-03 from the National Institute of Neurological Diseases and
Blindness, National Institutes of Health, United
States Public Health Service.
"Fellow, Fight-for-Sight Research Fellowship F
171.
144
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Volume 3
Number 2
Study of trabecular meshwork and scleral spur 145
Even in blood vessels, however, where
one expects to find elastic tissue in a more
typical form, there are divergent opinions
concerning its fine structure. According to
one view, it is thought to contain fibrillar
components in an homogenous or amorphous matrix, s"11 whereas another suggests
that it consists, basically, of vesicular components.1'- 13
The main purpose of the present study
was to determine the fine structure of the
structures in the anterior chamber angle
which, based on conventional methods,
have been considered to be elastic fibers,
and also to discover any similarities between their fine structure and that of the
elastic tissues of the aorta.
Material and method
Two young human eyeballs, one of a white
male 6 months of age and another from a white
female 3Vfe years of age, and aortas of adult
guinea pigs were used in this study. The human
eyes were removed surgically because of orbital
tumor or retinoblastoma, but the anterior segments
were clinically normal and no sign of glaucoma
was recognized. The guinea pig aortas and, immediately after enucleation, the anterior chamber
angle tissue of the human eyes were fixed in
1 per cent osmium tetroxide, buffered to pH 7.4
with Veronal acetate (Palade) containing sucrose.11 After 2 hours of fixation they were embedded in Epon following Luft's15 method.
Epon-embedded tissues were cut in a series of
thin sections for electron microscopy, and one
adjacent thick (1 to 2 fi) section for light microscopy with a LKB-Ultrotome. Other pairs of two,
adjacent (1 to 2 n and 2 to 3fi) sections were
also made for light microscopy to compare Giemsa
and Weigert stained material. The sections of the
eye were cut in both the anteroposterior and
tilted frontal planes.16 The latter plane is perpendicular to the former, with respect to a
limited area. The thin sections were stained with
lead,17- 1S uranyl acetate, and 0.2 per cent PTA
(phosphotungstic acid), and observed with a
Siemens Elmiskop II. For light microscopy, the
thick sections were stained with Weigert's elastic
or Giemsa's stain according to the following procedures.
Weigert's resorcin-fuchsin staining. The thick
sections (2 to 3 /*) were floated on drops of
distilled water on clean glass slides, and dried on
a hot (100° C.) plate. The sections mounted on
the slide were stained, without removing the embedding material, in a solution of 1 part com-
mercial resorcin-fuchsin solution and 1 part 70
per cent alcohol containing 1 per cent HCL, for
3 to 10 days. After differentiating rapidly with
absolute alcohol, they were mounted with balsam.
Giemsa staining. Thick ( 1 to 2 /i) sections,
mounted as before, were stained in a 10 per cent
Giemsa solution buffered to pH 7.2 for 12 to 24
hours, without de-embedding. The staining time
thus was prolonged to improve contrast. Unfortunately, this sometimes caused a reddish precipitate on the section, which was removed by dipping it in alcohol, thereby causing some loss in
the reddish tone of the whole tissue. By restaining
with Giemsa for at least 3 more hours, the original
color was recovered without appreciable precipitate. After washing with water, the slide was
dried and mounted with balsam.
Result
Light microscopy. The elastic fibers of
guinea pig aortas were stained a clear
dark purple with Weigert's stain (Fig. 8).
The same result was obtained with this
procedure when applied for a much shorter
time to the aorta of the same animals prepared by conventional (paraffin-embedded) histologic methods. Anteroposterior
sections of the human eye showed numerous fine dark purple dots in both the
trabecular meshwork and the scleral spur
when stained with Weigert's stain (Figs.
1 and 3). However, the other tissue components were poorly differentiated with
this procedure. Sections stained with
Giemsa, on the contrary, stained most of
the tissue components well (Figs. 2 and 4).
In Giemsa stained preparations, the dark
purple dots shown with Weigert's stain
were recognized as greenish dots. The
identity of the structures was proved by
comparing adjacent serial sections, one
stained with elastic stain and the other
with Giemsa (Figs. 3 and 4). These dots
were distributed almost throughout the
corneoscleral meshwork, endothelial meshwork,19 and scleral spur, although in some
portions of the endothelial meshwork they
were observed only occasionally. In the
corneoscleral meshwork, parallel rows of
these dots, as described by Salzmann,-0
were sometimes observed. These dots were
located also in the central zone of individual trabecular beams, as had been ob-
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Investigative Ophthalmology
April 1964
146 Iwamoto
served by Ashton and associates10 and
Shikano and Iwamoto.7 They were rarely
found in the uveal meshwork. Trabecular
meshwork in the tilted frontal sections
showed many long, rather straight lines
stained dark purple with Weigert's elastic
stain (Fig. 5) and greenish with Giemsa's
(Fig. 6). They were located within individual beams of the trabecular meshwork. These lines ran parallel to the long
axis of Schlemm's canal, that is, circularly.
This finding again confirms that of Ashton
and associates.10 Similar long lines, oriented circularly, were also observed in the
connective tissue of the scleral spur in the
tilted frontal section (Fig. 7). From this
observation it is concluded that the numerous dots in the anteroposterior section are
cross sections of the long, circularly oriented fibers which were stained dark purple
with Weigert's elastic stain, and that they
are the same structures which usually have
been thought to be elastic tissue of these
areas.
Electron microscopy.
Anteroposterior section. By comparing
the electron micrographs of thin sections
with the light micrographs of the adjacent
thick section stained with Giemsa, the fine
structure of the previously mentioned dots,
seen in the anteroposterior section with the
light microscope, was studied (plates 2 and
3). The dotlike structures seen in the light
micrographs were round, oval, or irregular
in shape (Figs. 11, e, 14 to 17 e, and 21 to
23). Occasionally they were long and flattened (Fig. 16, arrow). Each of the structures could generally be divided into two
areas, a peripheral cortex and a central
core, the boundary of both the areas having
a gradual transition. The peripheral cortex
consisted of densely distributed, very fine
dots 70 to 120 A in diameter (Figs. 11, 14,
21, p, and 22, p). When this structure was
cut obliquely, the cortex appeared to be
composed of parallel, fine filaments instead
of dots (Fig. 15, arrow). Even in a typical
cross section of these structures, however,
it was found that these fine dots were often
arranged in a beaded line (Fig. 21, p).
In the central core similar, but slightly less
dense, dots were distributed sparsely, in
most cases presenting a networklike pattern, in a less dense amorphous matrix
(Figs. 21, c and 22, c). This was particularly true in preparations stained with lead
or uranyl acetate. In such preparations,
when viewed at low magnification, these
The line on each electron micrograph indicates 1.2 microns.
Plate 1. Light micrographs of osmium-fixed, Epon-embedded sections.
Fig. 1. Weigert's elastic stain. Anteroposterior section of human anterior chamber angle.
Weigert's stained structures are seen as black dots. (x300.)
Fig. 2. Giemsa stain. This micrograph shows the same field as that of Fig. 1, taken from
the immediately adjacent section, t, trabecular meshwork; s, scleral spur. (x300.)
Figs. 3 and 4. Higher magnification of the areas encircled by the dotted line shown in Figs.
1 and 2, respectively, showing that the dots stained dark purple (black in the picture) with
Weigert's stain (Fig. 3) are seen as greenish dots (black in the picture) with Giemsa stain
(Fig. 4) (xl,140.)
Figs. 5 and 6. Tilted frontal sections of the trabecular meshwork stained with Weigert's and
Giemsa's stain, respectively. Long fibers stained dark purple (Fig. 5) and greenish (Fig. 6)
are seen as black lines, sc, Schlemm's canal. (x510.)
Fig. 7. Tilted frontal section of the scleral spur. Long fibers similar to those in Fig. 5 are seen.
Weigert's stain. (x510.)
Fig. 8. Weigert's stained aorta of a guinea pig. Elastic tissues are stained dark purple (black in
the picture). (x510.)
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Volume 3
Number 2
Study of trabecular meshwork and scleral spur 147
I
sc
JL
Plate 1. For legends see opposite page.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
148 Itcamoto
Plate 2. For legends see page 153.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Investigative Ophthalmology
April 1964
Volume 3
Number 2
Study of trabecular meshwork and scleral spur 149
\
Ct
. ct
Plate 3. For legends see page 153.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
14
Investigative Ophthalmology
April 1964
150 Iwamoto
m
cc
\
\
bm
ct
Plate 4. For legends see page 153.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Volume 3
Number 2
Study of trabecular meshwork and scleral spur 151
Plate 5. For legends see page 153.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Investigative Ophthalmology
April, 1964
152 Iwamoto
24
Plate 6. For legends see page 153.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Volume 3
Number 2
Study
J
of trabecular
meshwork
'
and scleral spur
r
Plate 2. Anteroposterior sections of the trabecular meshwork showing a comparison of election
micrographs (Figs. 9 and 11) with a light micrograph (Fig. 10).
Figs. 9 and 10. Fig. 9 is stained with lead. This field of the electron micrograph corresponds
to that encircled by a dotted line in the Giemsa stained photomicrograph (Fig. 10) of the
section immediately adjacent to the one shown in Fig. 9. Structures which correspond to the
dots stained greenish with Giemsa (Fig. 10, arrows) are shown by arrows in Fig. 9.
Fig. 11. Higher magnification of the structures (e) shown by the arrows in Fig. 9. bm,
basement membrane; en, endothelium.
Plate 3. Anteroposterior sections of the scleral spur showing a comparison of electron micrographs (Figs. 12 and 14) with a light micrograph (Fig. 13).
Figs. 12 and 13. Fig. 12 is stained with lead. This field of the electron micrograph corresponds to the area surrounded by a dotted line in Fig. 13, which is a light micrograph of
the section (Giemsa stain) immediately adjacent to that of Fig. 12. Compare the dots shown
by arrows in Fig. 13 with the structures shown by arrows in Fig. 12; they are the identical
structures.
Fig. 14. An electron micrograph taken at a higher magnification of the structures (e) shown
by arrows in Figs. 12 and 13. ct, connective tissue cell.
Plate 4. Anteroposterior sections of the trabecular meshwork (Figs. 15 and 16) and of the
scleral spur (Fig. 17) showing the distribution of those structures (e) which correspond to
the dots stained greenish with Giemsa, shown in plates 2 and 3.
Figs. 15 and 16. Fig. 15 is stained with lead, and Fig. 16 with uranyl acetate. Both figures
show individual beams of the corneoscleral meshwork. en, endothelium; bm, basement membrane; cc, collagen core.
Fig. 17. Scleral spur, stained with lead, ct, connective tissue cell.
Plate 5. Tilted frontal sections of the trabecular meshwork (Fig. 18) and of the scleral spur
(Figs. 19 and 20) showing longitudinal sections (e) of those structures shown in plates 2
to 4.
Fig. 18. Trabecular meshwork, stained with uranyl acetate, en, endothelium.
Fig. 19. Scleral spur, stained with lead, ct, connective tissue cell.
Fig. 20. Higher magnification of the region encircled by a white line in Fig. 19. p, peripheral
cortex; c, central core.
Plate 6. Figs. 21 to 23. Anteroposterior sections of the trabecular meshwork (Figs. 21 and 22)
stained with lead, and scleral spur (Fig. 23) stained with PTA, showing the detailed anatomy
of the structures stained with Weigert's and shown in plates 2, 3, and 4. p, peripheral cortex;
c, central core; cf, collagen fibrils.
Figs. 24 and 25 show elastic fibers of a guinea pig aorta stained with lead. Fine filamentous
structures are seen (arrow) surrounding elastic tissue. Fine fibrillar structures are seen in the
matrix of the elastic tissue, el, elastic tissue.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
153
Investigative Ophthalmology
April 1964
154 Iwamoto
structures appeared to be fairly dense
amorphous clumps having less dense central areas (Figs. 9, arrow; 12, arrow; and
17, e). When phosphotungstic acid (PTA)
was used, the central area (core) was seen
as a more dense amorphous mass with a
complicated spotted pattern (Fig. 23, c).
The gross distribution of these structures
in the trabecular meshwork and scleral spur
was the same as that of those stained with
Weigert's or Giemsa and seen with the
light microscope. In each beam of the
corneoscleral meshwork they were located
in both the peripheral and central parts
(Figs. 15, e, 16, e, and 11, e) of the collagen core, which in most places was
covered with either a thick or thin basement membrane (Figs. 11, bm, 15, bm, and
16, bm) beneath the endothelium. The
definition of basement membrane in this
paper is the same as that by Spelsberg and
Chapman.0 Those structures occupying the
peripheral part of the collagen core were
sometimes arranged in a row parallel to
the inner surface of the endothelium, as if
they ensheathed the central part of the collagen tissue (Fig. 16, e). The scleral spur
was composed of many irregularly shaped
compartments or bundles of collagen tissue,
each compartment being divided incompletely by a network of connective tissue
cells (Figs. 12 and 17). The Weigert's and
Giemsa stained structures were also distributed in both the peripheral and the
central part of each of these compartments
(Figs. 12, arrow; 14, e; and 17, e). Those
located in the peripheral zone of the compartments of the scleral spur (Fig. 12,
arrow), which were in general more common than those in the central zone, frequently formed a row parallel to the
boundary of the plasma membrane of the
connective tissue cells, which in most
places lacked a basement membrane.
Tilted frontal sections. Long rodlike
structures corresponding to the long fibers
seen in light microscopy were observed in
both the beams of the trabecular meshwork
(Fig. 18, e) and the collagen tissue of the
scleral spur (Fig. 19, e). In a typical
longitudinal section (Fig. 20) passing
through the center of these long structures,
two areas, a peripheral and central, were
distinguishable. Both areas consisted of
parallel rows of long, fine filaments, the
direction of which was parallel to the long
axis of the entire structure. In the peripheral area, which is considered to correspond
to the peripheral cortex seen in the anteroposterior section, these fine filaments 70
to 120 A in width were compactly arranged,
and, in a typical case, each was beaded
with fine dense dots about the same size in
diameter as the width of the filament (Fig.
20, p). This beaded pattern of the filament
was more frequently observed in the scleral
spur than in the trabecular meshwork.
Parallel arrays of these beads occasionally
presented a pattern of about 600 A periodicity (Fig. 20,.arrow). In the central area,
which is considered to correspond to the
central core seen in the anteroposterior
section, the filaments were a little less dense
than in the peripheral, and their beaded
pattern was less noticeable. They were arranged rather sparsely in a matrix that was
less dense when stained with lead or uranyl
acetate (Fig: 20, c).
It is, therefore, believed that each of the
circularly orierited.long fibers which stained
dark purple with Weigert's elastic stain
had a fine structure, the cross section of
which was as described in the anteroposterior section and the longitudinal section in the tilted frontal section.
Discussion
The method of study of alternate thin
sections for electron microscopy and adjacent thick sections for light microscopy has
been used by several investigators21"25 in
order to identify tissue components seen
in electron micrographs. This method was
applied in the present study, and the thick
sections were stained with Giemsa. Giemsa
staining on the de-embedded methacrylate
material has been used for other tissues.21'22
In this study, a procedure for staining
Epon-embedded material without de-embedding was modified as described above.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Volume 3
Number 2
Study of trabecular meshioork and scleral spur 155
It is believed that those tissues which
were stained dark purple with Weigert's
elastic stain and greenish with Giemsa in
the trabecular meshwork and in the scleral
spur are the same as those which had been
considered to be elastic tissues.1'1' -° Garron
and Feeney1 considered that the elastic
tissues observed by conventional methods
were identical to the clumps of 1,000 Abanded material seen in electron microscopy. However, in the young human eyes
used in this study, 1,000 A-banded material
was only rarely observed, confirming the
finding of Leeson and Speakman/' In contrast, there were numerous dots stained
with Weigert's elastic stain in anteroposterior sections. The fine structure of
these "dots" studied in electron micrographs
is very different from that of the 1,000 Abanded material. Rather, they may be
similar to the clumps of "amorphous, finely
fibrillar" material observed in the infant eye
by Leeson and Speakman.5 The location of
these structures in individual trabecular
beams and their appearance at low magnification resemble the elastic fiberlike structures reported previously,7 although there
are some differences due perhaps to the
age of the tissue, the methods of preparing
the tissues, and also the resolving power
of the electron microscope. We have not
yet determined whether the 1,000 A-banded
material is also stained with Weigert's
elastic stain. This study is continuing with
use of adult human eyes in which the 1,000
A-banded material is presumably more
prevalent than that in the young human
eyes/'' 7
The fine structure of each of the Weigert's
positive tissues consisted of a peripheral
cortex and a central core. The former consisted of compactly arranged, fine filaments
in which a beaded pattern was frequently
observed. Similar filaments or fine fibrils
with or without beaded pattern have been
observed in the trabecular meshwork1' 2>G> 29
as well as other tissues,10' 2G"30 some of
which were thought to be related to collagen."- 10' 2(i~29 The true nature of these filaments in the peripheral cortex is not clear,
but it is possible that they are related to
collagen. The fine structure of the central
core was different from that of the peripheral cortex, although similar but less dense
filaments without a clear, beaded pattern
were observed in its matrix.
A study was made to determine if any
similarity could be found between these
structures and the elastic tissues of the
guinea pig aorta. Some similarity between
the two was found. The elastic tissues of
the tunica media and adventitia of the aorta
appeared less dense and amorphous when
stained with lead (Figs. 24 and 25, el).
Fine filamentous or fibrillar structures were
sometimes observed in the matrices of the
elastic tissues (Figs. 24 and 25, el), as had
been observed in the aortas of other
animals.9"11 These two facts may suggest the
similarity between the central core of the
structures in the anterior chamber angle
tissue and the elastic tissue of the aorta.
Furthermore, fine filamentous structures
were sometimes observed surrounding the
elastic tissues of the aorta (Figs. 24, arrow
and 25, arrow), as had been observed in
other animals.10-T1 These filamentous structures might correspond to the peripheral
cortex of the above stated structures. Therefore, it seems possible that the central core
of these structures may be a form of
elastic tissue, although their detailed structure is not quite identical to that of elastic
tissues in the aorta.
I wish to thank sincerely Professor George K.
Smelser for suggesting this problem and for his
continuing interest, advice, and encouragement.
I appreciate the help of Miss Ozanics and Miss
Cubberly and am grateful to Drs. Ira Jones and
Robert Ellsworth for the surgical material.
REFERENCES
1. Garron, L. K., and Feeney, M. L.: Electron
microscopic studies of the human eye. II.
Study of the trabeculae by light and electron
microscopy, A. M. A. Arch. Ophth. 62: 966,
1959.
2. Garron, L. K.: The fine structure of the
normal trabecular apparatus in man, in Newell, F. W., editor: Glaucoma. Transactions
of the fourth conference, New York, 1959,
Josiah Macy, Jr. Foundation, p. 11.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017
Investigative Ophthalmology
April 1964
156 Iwamoto
3. Holmberg, A.: The fine structure of the inner
wall of Schlemm's canal, A. M. A. Arch.
Ophth. 62: 956, 1959.
4. Holmberg, A. S.: Ultrastructure of the normal
trabecular apparatus in man, in Newell, F.
W., editor: Glaucoma. Transactions of the
fourth conference, New York, 1959, Josiah
Macy, Jr. Foundation, p. 59.
5. Leeson, T. S., and Speakman, J. S.: The fine
structure of extracellular material in the
pectinate ligament (trabecular meshwork)
of the human iris, Acta Anat. 46: 363, 1961.
6. Spelsberg, W. W., and Chapman, G. B.: Fine
structure of human trabeculae, A. M. A.
Arch. Ophth. 67: 773, 1962.
7. Shikano, S., and Iwamoto, T.: Electron- and
light-microscopic studies on the human trabecular meshwork, Japanische Monatsschr.
praktische Augenh. 56: 765, 1962.
8. Parker, F.: An electron microscope study of
coronary arteries, Am. J. Anat. 103: 247,
1958.
9. Keech, M. K.: Electron microscope study of
the normal rat aorta, J. Biophys. & Biochem.
Cytol. 7: 533, 1960.
10. Karrer, H. E.: Electron microscope study of
developing chick embryo aorta, J. Ultrastruct.
Res. 4: 420, 1960.
11. Karrer, H. E.: An electron microscope study
of the aorta in young and in aging mice, J.
Ultrastruct. Res. 5: 1, 1961.
12. Pease, D. C , and Molinari, S.: Electron
microscopy of muscular arteries. Pial vessels
of the cat and monkey, J. Ultrastruct. Res.
3: 477, 1960.
13. Paule, W. L.: Electron microscopy of the
newborn rat aorta, J. Ultrastruct. Res. 8:
219, 1963.
14. Caulfield, J. B.: Effects of varying the vehicle for OsO4 in tissue fixation, J. Biophys.
& Biochem. Cytol. 3: 827, 1957.
15. Luft, J. H.: Improvements in epoxy resin
embedding methods, J. Biophys. & Biochem.
Cytol. 9: 409, 1961.
16. Ashton, N., Brini, A., and Smith, R.: Anatomical studies of the trabecular meshwork
of the normal human eye, Brit. J. Ophth. 40:
257, 1956.
17. Millonig, C : A modified procedure for lead
staining of thin sections, J. Biophys. & Biochem. Cytol. 11: 736, 1961.
18. Karnovsky, M. J.: Simple methods for "stain-
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
ing with lead" at high pH in electron microscopy, J. Biophys. & Biochem. Cytol. 11: 729,
1961.
Speakman, J. S.: Drainage channels in the
trabecular wall of Schlemm's canal, Brit. J.
Ophth. 44: 513, 1960.
Salzmann, M.: The anatomy and histology
of the human eyeball in the normal state.
Its development and senescence, Chicago,
1912, University of Chicago Press.
Nakamura, S., and Fujiwara, T.: Studies on
the ultra-thin sectioning with high efficiency
(III), Electron-microscopy 8: 188, 1959.
Segawa, K.: Correlated electron and light
microscopic studies on conjunctival cells infected with type 8 adenovirus and on conjunctival epithelial cells in epidemic keratoconjunctivitis, Acta Soc. ophth. Jap. 65:
1090, 1961.
Trump, B. F., Smuckler, E. A., and Benditt,
E. P.: A method for staining epoxy sections
for light microscopy, J. Ultrastruct. Res. 5:
343, 1961.
Yardley, J. H., and Hendrix, T. R.: Combined
electron and light microscopy in Whipple's
disease. Demonstration of "bacillary bodies"
in the intestine, Bull. Johns Hopkins Hosp.
109: 80, 1961.
Welsh, R. A.: Light and electron microscopic
correlation of the periodic acid-Schiff reaction in the human plasma cell, Am. J. Path.
40: 285, 1962.
Karrer, H. E.: The fine structure of connective tissue in the tunica propria of bronchioles, J. Ultrastruct. Res. 2: 96, 1958.
Gross, J., Sokal, Z. and Rougvie, M.: Structural and chemical studies on the connective
tissue of marine sponges, J. Histochem. &
Cytochem. 4: 227, 1956.
Jackson, S. F., and Smith, R. H.: Studies
on the biosynthesis of collagen. I. The growth
of fowl osteoblasts and the formation of collagen in tissue culture, J. Biophys. & Biochem. Cytol. 3: 897, 1957.
Jakus, M. A.: The fine structure of the
human cornea, in Smelser, G. K., editor: The
structure of the eye, New York, 1961, Academic Press, Inc., p. 343.
Schwarz, W.: Electron microscopic observations of the human vitreous body, in Smelser,
G. K., editor: The structure of the eye, New
York. 1961, Academic Press. Inc., p. 283.
Downloaded From: http://iovs.arvojournals.org/pdfaccess.ashx?url=/data/journals/iovs/933630/ on 06/15/2017