Maximilian Salzmann.

The anatomy and histology of the human eyeball in the normal state, its development and senescence ; online

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of Stilling, 212; canalis hyaloideus or Cloquet's canal). This begins in
front of the papilla in a funnel-form widening (area martegiani} and courses
through the vitreous in an almost sagittal direction. Its width is i to
2 mm; the free end sometimes narrows to a point and usually strikes the
lens nasal to its posterior pole. According to Bribach (27), the canal only
extends 4 mm from the papilla into the vitreous in some eyes, and splits
up into a few fine branches.

In order to make the canal visible one must inject it; according to
Stilling, this often succeeds merely by simply dropping a colored solution
onto the posterior surface of the freed vitreous. According to Schwalbe,
one may also obtain a filling of the central canal by an injection beneath
the pial sheath of the optic nerve. According to the latest demonstra-
tion of Stilling (Zeitschrift fur Augenheilkunde, Bd. 25, S. 15), a narrow
canal is found in the mammalian eye only in the newborn; in the devel-
oped human eye, on the other hand, a wider lymph space is present;
this is filled out by a soft, tortuously folded substance.

On the other hand, Wolfrum (239)- denies the existence of a preformed canal in
th's situation, and explains the central canal as an artificial product arising by the
tearing off of the vitreous from the papilla. In this matter the hypothesis of Stilling
has been completely corroborated by the newer investigations of Schaaff (189) and
Bribach; the latter has, moreover, published stereoscopic photographs of the injected
canal.

In the fresh state the vitreous presents a completely transparent
entirely colorless mass of jelly-like but firm consistency.

The vitreous exceeds all of the other refracting media of the eye
in transparency with the exception of the aqueous. In its optical rela-
tions it agrees with the latter and with water; according to Freytag (61),
its index of refraction is i .3334 to i .3350 (a mean of i .334). Moreover,
the vitreous maintains this transparency a long time after death (even
in a weak formalin solution) ; it merely becomes thready and of lessened
consistence.

Even in this condition the microscopic examination does not bring
out the least trace of a structure in the vitreous, and so it is conceivable
that in earlier periods, when none of the modern histologic aids were
available, one did not understand how to begin to study the vitreous,



1 50 ANATOMY AND HISTOLOGY OF THE HUMAN EYEBALL

and that the most varied views concerning its structure were expressed.
Indeed, even the existence of such a structure was denied.

That it must, however, possess such is evident from the fact that it
has a form and a consistency of its own; its elements do not flow apart
over its supporting base, it can be weighed, etc. (H. Virchow, 233).
One can press fluid out of it or filter it off from the incised vitreous; it
apparently consists, therefore, of a framework of firmer substance and a
fluid filling out the meshes of the latter.

But an idea of the arrangement of the elements of the framework
can only be obtained from hardened preparations. On account of the
delicacy of the structure the sections should not be too thin but very
strongly stained. Retzius (180) used rubin for this, I myself have used
the phospho-molybdic-acid hematoxylin of Mallory, yet many other
stains give good results.

It then develops that the whole framework of the vitreous goes out
from the base of the vitreous. Out of the somewhat complicated fibrilla-
tion of this portion a thicker layer is first separated off and this extends
along the inner surface of the retina backward as the posterior border layer
(PI. I, hG). Even by low-power magnification one sees a fine striation
parallel to the surface and usually slight waviness, which is probably the
result of the shrinking of the tissue in the imbedding a peculiar picture
which one does not find in any other tissue of the eye and which I can
only compare with the flowing hair of a woman. The posterior border
layer is thickest immediately at the or a serrata; farther backward it is
always thinner, since the innermost layers constantly turn off into the
interior of the vitreous. In this way the posterior border layer finally
breaks up entirely and, indeed, the border layer is in pretty firm union
with the membrana limitans interna retinae opposite the entrance of the
optic nerve in the area martegiani, and when the vitreous is detached as
a result of the hardening the limitans follows, as a rule.

That portion of the fibrillation of the base of the vitreous which does
not enter the posterior border layer, radiates into the interior of the
vitreous, broadening out like a fan, and forms the loose, often shreddy,
body of the vitreous, along with the branches of the border layers.

As above reported, the anterior border of the base of the vitreous lies
about i . 5 mm in front of the ora serrata, that is, the more compact mass
of the base of the vitreous is inserted as a wedge about this distance away.
Yet a very loose framework extends still farther forward to the middle of
and even beyond the orbiculus ciliaris and then is gradually lost.

About the middle of the orbiculus ciliaris, therefore about 2 mm in
front of the ora serrata, a thickening of the framework of the vitreous



THE VITREOUS 151

again appears. This often begins with a pretty sharp border in the
above-reported looser framework and stretches out from there over the
whole of the anterior surface of the vitreous. It separates the vitreous
from the posterior chamber and from the lens and is, therefore, called the
anterior border layer (PL I, vG). Like the posterior border layer it
shows a striation parallel to the surface and is easily thrown into circular
folds.

The anterior border layer is much thinner than the posterior and main-
tains this thickness unchanged up to the border of the lens; it then thins
out in the territory of the lens and in the middle of the patellar fossa
reaches a minimum without wholly dissolving away. As in the posterior
border layer, the thinning comes about by a variation off into the body of
the innermost layers.

Naturally, the anterior border layer is sharply bordered off from
the posterior chamber, but it is also much more sharply set off inward
(toward the body of the vitreous) than is the posterior border layer. It
therefore gives the impression of a membrane in many eyes in cross-
section, especially when it has been compressed by hardening and when its
thickness does not exceed that of the lens capsule. This is the reason
why many authors speak of a hyaloidea in this section of the vitreous.
This hyaloidea is identical with the anterior border layer. Proof of this
is furnished by its histologic structure, and this will be discussed later.

The anterior border layer can easily be prepared as a continuous
coat, and when laid out flat it presents a circular disk about 18 mm in
diameter.

To prepare the anterior border layer one chooses an eye which has been well fixed
in Mueller's fluid, halves it at the equator, and carefully removes the loose shreds of the
vitreous body from the anterior segment. If one can keep from touching the wall of
the eye in doing this the body can be completely removed without injuring the border
layer.

One now separates the retina bluntly from the ora serrata and carefully removes
everything remaining in connection with the retina. A greater resistance is felt first
at the posterior border of the corona ciliaris and then at the border of the lens, yet
this can be overcome by pulling on the already detached portions.

The whole of the tissue detached in this way is stained deeply, incised radially,
and laid out flat. Aside from the entire anterior border layer, such a preparation
contains the posterior half of the zonula, the base of the vitreous, and the border portion
of the retina. A simple pull backward on the base of the vitreous completely separates
the border layer from the portion clinging to it.

Prepared free in this way, the anterior border layer shows many
circular folds; in the region of the corona ciliaris the impressions of the
ciliary processes are visible as flat meridional furrows, and between these



152 ANATOMY AND HISTOLOGY OF THE HUMAN EYEBALL

there sometimes lie delicate membranous clinging structures (the "liga-
mentes cordiformes" of Campos, 30), which likewise have a meridional
course. A portion of the zonula fibers have clung to the border layer
(innermost zonula fibers; see chap, xii), or have left fine canals impressed
on it; individual zonula fibers ray out into the border layer and go over
into circular fibers. Where the border layer clings to the lens, a darker
ring sometimes comes out and the stump of the ligamentum hyaloideo-
capsulare clings to it as a delicate circular fringed seam. 1

The most important difference, however, between the posterior and
the anterior border layer is that the posterior border layer is connected
with the membrana limitans interna retinae throughout, while the anterior
border layer is separated from the analogous membrana limitans interna
ciliaris by the posterior chamber. The separation is not everywhere a
complete one, in so far as the posterior chamber is in places crossed by
delicate extensions of the vitreous.

So the posterior zone of the anterior border layer is nevertheless very
much connected with the membrana limitans interna ciliaris and, indeed,
by means of fine vitreous fibrillae, which course from behind and within,
forward and outward, and wind in and out tortuously between the zonula
fibers which are numerous, even here.

Another system of vitreous extensions appears in the posterior part
of the corona ciliaris. Corresponding to each ciliary valley one often
sees here a wing-like process directed meridionally, elevating itself out of
the anterior border layer from a three-sided prismatic base; it then
divides up into very tortuous bands and finally into finest fibrillae, and
so ends at the membrana limitans interna ciliaris. These processes are
easiest seen in transverse sections going through the corona ciliaris (PL
VII, 2, Lc), and in them I think I have recognized the ligamentes cordi-
formes described by Campos (30).

A structure united to the lens capsule but not with the limitans
interna ciliaris and likewise belonging in the category of these extensions
of the vitreous is the already reported ligamentum hyaloideo-capsulare
(Wieger, 238).

Just in front of the place where the anterior border layer reaches the
lens capsule, a delicate fibrillar mass (PL I, Lhc} rises up out of the
border layer on a three-sided prismatic base and, diminishing in bulk,
extends along through the zonula fibers to the lens capsule. It can be
followed as far as the equator of the lens or, indeed, even beyond this
to the anterior zonula fibers. Its appearance has been described above



1 With respect to this and many other details not noted here I refer the reader to my monograph
(184)-



THE VITREOUS 153

in the surface preparation of the border layer; the dark ring at times
visible at this place does not really come from the ligament itself but
from a thickening of the border layer.

I have allowed the named used by Wieger for this structure to remain, because this
author is the only one who describes a special substratum structure for the fixation of
the vitreous to the lens. If his description differs to any extent from my own, this is
mainly due to the difference in technique. The name does not, indeed, fall in with the
nomenclature used by me, because I cannot look upon the border layer as the hyaloidea,
as Wieger does. It only surprises me that no one else has reported this extension of
the vitreous; as a matter of fact it is very easily seen after ordinary staining.

It does not need to be proven that this structure has a relationsh p to the fetal
tunica vasculosa lentis, for throughout it corresponds in its position to this fetal struc-
ture. When, however, I speak of this as a remnant of the vascularized fetal lens
capsule, it is not to be taken literally. The ligament does not arise out of the vessels of
this capsule; ectodermal vitreous tissue has simply developed along these vessels.

It is made clear from this description, therefore, that the vitreous
possesses throughout a thicker rind or border layer. This fails in only
two places: one is the area martegiani, the entrance to the central canal;
the other lies between the base of the vitreous and the margin of the
anterior border layer. This latter has the form of a circular cleft and on
account of its relation to a portion of the zonula fibers I have called this
place the zonular cleft (184) (PL I, Z). The zonular cleft is, however,
not a free open space, but only a place where the delicate framework of
the body of the vitreous comes out onto the surface. Whether or not,
as Kuschel (153) thinks, it is an efferent for the fluid of the vitreous
must first be established by experimental means.

The question whether or not the vitreous has a surrounding mem-
brane of its own, a hyaloidea, has long been a matter of contention. In
post-mortal or artificial detachment of the vitreous from the retina, in any
case, one sees a plain membrane on its inner surface as a rule, but this
is nothing more than the membrana limitans interna retinae (see p. 79).
It is a matter open to discussion whether this covering belongs to the
retina or to the vitreous, and in keeping with this, one may call it either the
membrana limitans interna retinae, or the hyaloidea as the case may be;
but one thing is certain: aside from this, no other (second) membrane
exists between the bases of the Mueller's fibers and the border layer of the
vitreous.

The vitreous tissue consists of a framework of extremely delicate and
soft fibrillae and of a fluid lying in interspaces. Both substances must
possess exactly the same refracting capacity, otherwise it would be impos-
sible to account for the complete transparency of the vitreous.



154 ANATOMY AND HISTOLOGY OF THE HUMAN EYEBALL

Living fixed cells, blood-vessels, and nerve-fibers are entirely absent
in the fully formed vitreous.

Body (nucleus) and rind (border layer) are differentiated particularly
by the density of the framework and their texture. The nucleus is best
studied in teased preparations : one tears out the loose body shreds with a
pincette and stains them a few hours with Mallory's hematoxylin. High
power then shows numerous fine fibrillae closely interwoven and forming
a tissue having the appearance of a spider-web. The fibrillae are immeas-
urably fine and extremely soft, and the whole framework can be very
easily distorted. Angular granules are found strewn about here and
there in this framework, and are considered by Wolfrum (239) to be the
end processes of the embryonic radial vitreous fibers (cf. chap. xvi).
Moreover, one ordinarily sees a fine granular precipitate upon the fibrillae.
This probably arises out of the fluid of the vitreous.

Since such a vitreous shred is drawn out when it is torn away and
bruised by the pincette and pressed down flat by the coverslip, such a
preparation can give only an approximate idea of the structure of the
fibrillae and their number. , The actual texture of the body of the vitreous,
the interweaving of the fibrillae in all three directions, in short, the
framework which it forms, can only be made out in sections; these,
however, must not be too thin, because of the delicacy of the tissue. On
the other hand, the border layers consist of a large number of very delicate
superficially parallel lamellae, and the striation which they show upon
cross-section is only the optical cross-section of these lamellar systems
and appears the same whether the section is meridional or transverse.
The lamellation of the border layer comes out very plainly in surface and
teased preparations. In the first place, there is no difficulty in splitting
the border layer parallel to the surface, and each of the membranes
obtained in this way furthermore shows a large number of lamellae,
which one can recognize in microscopic study, especially by the terrace
formation.

Each lamella consists of a net of fibrillae. These are much finer even
than the fibrillae of the body. They are so fine that the net cannot be
completely traced out optically, even with the strongest magnifications,
although the lamellae do not appear homogeneous even in moderately
high magnifications.

When the individual lamellae are followed from within outward, an
increasing fineness of the elements and an increasing density of the net is
made out. Yet the most peripheric lamella that bordering immediately
on the posterior chamber is not entirely homogeneous, although it
acts very much like a homogeneous membrane in all of its relations.



THE ZONULA CILIARIS 155

The angular granules seem to be entirely absent in the border layers;
on the other hand, living cells are found on the outer surface of the pos-
terior border layer and at the vitreous base also. These have been called
the subhyaloid cells by some authors (PI. V, 8). They do not form a
continuous coat. They are wholly isolated cells separated by fairly wide
interspaces, provided with simple or fragmented nuclei and a granular
protoplasm. It is relatively seldom that these cells are round; for the
most part they show several processes, often possess node-form or vesicular
thickenings. When the protoplasm contains larger vesicles with a clear
content, they are called physaliphores. All these cell forms are to be
considered wandering cells; the absence of the closed union and the
presence of amoeboid movements, which Iwanoff (113) saw in them in the
living vitreous, speak for this.

There are no membranes inside the vitreous. A few authors, as Straub (215),
consider the vitreous to be made up of a large number of membranes, but the con-
ception apparently has its origin in unsuitable fixation; in pathologic cases also the
fibrillae so press together that a membrane is simulated.

According to Addario (3), the vitreous fibrillae come out of the apices of the inner
extensions of the ciliary epithelium (cf. p. 122), and on this basis he considers the pos-
terior zone of the ciliary epithelium to be the matrix of the vitreous. There is much
to be said for this view: the firm unions of these parts, the development of the defini-
tive vitreous, the deleterious influence which inflammations of the ciliary body have
upon the vitreous; but the transition of the vitreous fibrillae into the ciliary epithelium
in the adult eye probably should not be taken so literally; the two kinds of tissue are
sharply separated from one another.

Tornatola (224) even conceives of a connection of the vitreous fibrillae with
Mueller's supporting fibers of the retina. Whoever believes in the existence of the
membrana limitans interna retinae cannot agree with the view of Tornatola (cf. p. 79).

CHAPTER XII. THE ZONULA CILIARIS (Z. ZINNII, LIGAMENTUM

SUSPENSORIUM LENTIS)

By the zonula one understands that system of fibers spanned out
between the inner surface of the ciliary body on the one side and the
equatorial zone of the lens and the anterior border layer of the vitreous
on the other side ; it mainly fixes the lens in its position and has an effect
upon the form of the lens through the function of the ciliary body.

In order to obtain a general view of the zonula one looks at the anterior
segment of the eyeball from behind under intensely focalized light and
moderate magnification (PL IV, 10). One then perceives, even in the
anterior portion of the orbiculus ciliaris, a fine, silk-like, shiny meridional
striation (better seen in hardened eyes than in fresh ones), which extends
into the ciliary valleys but leaves the processes free. From the middle of



i S 6 ANATOMY AND HISTOLOGY OF THE HUMAN EYEBALL

the corona on, fine, shiny, still very plainly separated fibers come out
of the ciliary valleys close to the processes and course over the anterior
part of the corona through the circumlental space to the posterior surface
of the lens. The fibers are apposed to the side surfaces of the processes,
so that they appear to come from them, and each ciliary process is flanked
by two rows of zonula fibers. A similar picture is obtained in the view
from the front after the removal of the iris: two fiber-bundles appear
to run from each ciliary process to the anterior surface of the lens.

The number of the processes is something like 70, so the zonula is
divided up into some 140' meridional rows or lamellae (Retzius, 180)
apposed to the ridges of the ciliary processes in the circumlental space
(the free portion of the zonula).

In order to obtain the zonula in a single preparation, one proceeds
as in the preparation of the anterior border layer. When one makes this
preparation from the hardened eye only the posterior half of the zonula
that from the ora serrata up to the posterior border of the corona ciliaris
comes into view. In the fresh eye, on the other hand, the zonula can be
prepared as a whole in this way, whereby, of course, the limitans interna
ciliaris and more or less of the epithelial covering of the ciliary body
comes away with it.

In this way one is very easily convinced that the posterior border of the
zonula, in so far as it forms a closed fiber layer, lies some i . 5 mm in front
of the ora serrata, therefore at the anterior border of the base of the vitreous.
This border, the posterior zonula border of many authors, reproduces the
form of the ora serrata in such a way that the border of each tooth is
correspondingly withdrawn from the corona, and the finer undulations of
the border of the retina correspond to the marked zig-zag outline of the
posterior border of the zonula. Like the large mesh zone of the reticulum
of H. Mueller (p. 118), the posterior border layer is, therefore, a carica-
ture of the ora serrata. But this posterior limit of the zonula is not the
limit of all the fibers. A minority of the fibers come from points lying still
farther back, and, indeed, a good many from the inner surface of the ciliary
body in the region of the base of the vitreous, and some few out of the
vitreous itself, partly as radiations into the body of the vitreous, partly
(on the nasal side) out of the posterior border layer in the neighborhood of
the ora serrata (PL I).

All of these fibers arising out of the vitreous or passing through the
base of the vitreous course through the zonular cleft and unite with the
main mass springing from the posterior border of the zonula. So many
fibers arise out of this that a closed layer of meridionally coursing fibers
covering up all the others at once forms and stretches over the whole



THE ZONULA CILIARIS 157

orbiculus ciliaris in this manner, lending to it the above-reported fine
striation.

If one wishes to be further oriented concerning the origin of the
zonula fibers and their topographical relations one must turn his attention
to sections. Such preparations then show that, with the exception of the
whitish crests of the processes, fine zonula fibers also go off from the entire
inner surface of the ciliary body as far as the sims and unite with those
coming from behind, already grown to larger fibers. So it comes about
that, in general, the larger zonula fibers lie inward over the orbiculus, i.e.,
toward the side of the vitreous, the finer fibers, on the other hand, outward,
i.e., on the side of the ciliary epithelum (PL VII, 2, 5, Z).

The direction of these fine fibers (auxiliary fibers, Gamier, 72) is,
in general, the same as that of the larger ones from behind and without,
forward and inward ; over the orbiculus they course almost parallel to its
inner surface; toward the front they mount up more and more abruptly,
and the most anterior are placed nearly perpendicular to the inner surface
of the ciliary body.

Moreover, aside from these straight coursing fibers, fibers which course
backward are found in the anterior part of the orbiculus and the posterior
part of the corona; these were called the orbiculo-ciliary fibers by
Czermak (34), i.e., fibers which course from without and in front back-
ward and inward. There arises thereby a narrow-angled crossing of the
fine zonula fibers very well seen in meridional section (Taf. I), for example,
just behind the corona ciliaris. This double anchorage brings about a
stronger fixation of the entire zonula fiber mass at the posterior border
of the corona ciliaris, and this is the reason why with few exceptions the
zonula fibers break away at this place.

Those which do not are relatively weak fibers coursing close to the


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Online LibraryMaximilian SalzmannThe anatomy and histology of the human eyeball in the normal state, its development and senescence ; → online text (page 18 of 27)