Maximilian Salzmann.

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

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born (see chap. xvii).

All things considered, one must conclude that the form of the ciliary muscle depends
upon its length, i.e., the longer the muscle from whatever cause, the more the myopic
type comes to expression, the shorter it is, the more the hypermetropic type comes out.
The transitory changes in its length, by contraction, have the same effect as the perma-
nent ones those which develop either as a congenital variation or as a result of the
elongation or shortening of the sagittal diameter of the eye.

The fibers which make up the ciliary muscle are ordinary smooth
muscle-fibers, although the nuclei are not so markedly rod-form but more
oval than is generally the case.

The blood-vessels peculiar to the ciliary muscle lie throughout in its
interstitial tissue and have a small caliber. The larger arteries encoun-
tered in horizontal sections of the ciliary muscle are the main branches
of the long posterior ciliary or anterior ciliary arteries,' for these vessels
course through the muscle; they usually lie in a large area which is free
from muscle-fibers.

Behind the root of the iris and in front of the circular portion of the
muscle or in it one encounters the cross-section of an artery, the circulus
arteriosus major, in all meridional sections; this vascular circle, therefore,
hardly belongs to the ciliary muscle, for its branches supply the ciliary
processes and mainly the iris. Large veins are not found in the ciliary
muscle ; its blood is partly carried backward by the smaller vessels of this
sort through the vessel layer, partly outward through the sclera; the latter
vessels are the venae ciliares anteriores; they also take care of the outflow
from the canals of Schlemm (see p. 44).

The ciliary nerves branch before entering the ciliary muscle, form
first a wide-meshed plexus, and then, continuing to branch, pass on
through the muscle. The nerves to the ciliary muscle itself, as well
as those for neighboring parts, are given off from this plexus. This is
particularly true of those for the iris and the deeper layers of the corona.
This plexus consists mainly of medullated fibers and, aside from larger
ganglion cells, usually contains small bipolar ganglion cells, which are
in all probability motor cells (H. Mueller, 159; Iwanoff, 115).

There are but few contributions extant upon the finer relations of the nerves of
the ciliary muscle. Agababow (4) has found motor endings in the muscle-fibers in the
shape of straight fibers, or fibers dividing at sharp angles, by the aid of the methyl-blue


stain, and end arborizations with pretty large branches ending by nodular expansions.
These lie in the interstitial connective tissue and were considered to be sensory endings
serving the muscle-sense. Finally, Agababow found the so-called reticular plate, i.e., an
extremely fine fibrillar net, which can only be resolved by the aid of the oil immersion
system. Yet accurate data concerning the situation of this layer is lacking.


This is a direct continuation of the vessel layer of the chorioidea, for
the vortex veins carry away the blood not only from the chorioidea but
also from the anterior portion of the uveal tract, especially from the iris
and the ciliary processes. Since, however, the arterial trunk for this vas-
cular region runs through the perichorioidal space and the ciliary muscle,
the vessel layer of the ciliary body contains only veins of varying caliber,
with the exception of a few arteries running back to the chorioidea.
These vessels course nearly parallel to one another and occasionally
anastomose at narrow angles at the vortices; therefore, one gets only
longitudinal or very oblique sections of these vessels on meridional cuts,
on the other hand, almost pure cross-sections on transverse cuts; in the
orbiculus ciliaris these vessels are broadened out into what is scarcely
more than a single layer, i.e., narrow and wide vessels lie on the same
plane (PL VII, 4, 5, Gf).

The larger elevations of the ciliary body, the ciliary processes, the
sims, the plicae ciliares, and the warts in the valleys are due to local thick-
enings of the vessel layer with a corresponding superimposition of the
vessel lamina. The ciliary muscle has no part in any of these formations;
its inner contour courses along straight beneath the elevations (PI. VII,
2), as the transverse section shows. In particular, each ciliary process
(Pc) conceals a richly subdivided framework of wide capillaries and
small veins supplied by a small artery from in front, and sends several
veins backward into the orbiculus ciliaris.

In respect to its histologic structure, the vessel layer of the ciliary
body also agrees with that of the chorioidea, except that the chromato-
phores are less numerous and almost completely disappear toward the
front in many eyes. The ciliary processes only exceptionally contain
chromatophores ; for this reason the collagenous connective tissue comes
out more prominently and is denser in this region. In the anterior
part of the ciliary processes especially (toward the iris root), this tissue
morphologically assumes a sclerosed appearance, and these places then
stain an intense red by Van Gieson. Fine elastic fibers are irregularly
intermixed with the collagenous tissue.



(PL VII, 4, 5, el)

This is a continuation of the lamella of the same name in the lamina
vitrea chorioideae and forms the inner limitation of the vessel layer in the
orbiculus ciliaris and posterior part of the corona ciliaris. In the orbiculus
ciliaris it is seen, after all stains, as a fine, very sharp straight line in
case the section goes perpendicular to the surface, for this lamella courses
absolutely smooth over the orbiculus ciliaris.

The slight wrinkling shown in PL VII, 4, 5 is brought about by a detachment
of the ciliary body from the sclera.

Naturally, it comes out still more plainly after elective staining for
elastic fibers, e.g., orcein. This stain resolves it into a net of elastic fibers.

With the transition to the elevations of the corona ciliaris, this smooth-
ness of the lamella is lost and it therefore disappears in the unstained
state at this place, for it is usually cut obliquely by the section. In the
orcein preparation it can, however, still be followed as far as the middle
of the corona. The fiber net constantly becomes looser and finally rays
off in irregular bundles into the collagenous tissue of the vessel layer.
This lamella cannot therefore be demonstrated over the anterior declivities
of the ciliary processes.

(PL VII, 4, 5, **)

This is evidently a continuation of the delicate layer of collagenous
fibrillae found by Wolfrum (240) between the two layers of the glass
membrane of the chorioidea (cf. p. 60). While special methods are
necessary to demonstrate the collagenous fibrillae in the chorioidea,
this connective-tissue layer attains such a thickness in the ciliary body
that ordinary stains, especially Van Gieson's stain, make it plainly visible.

For example, when one follows the lamina vitrea chorioideae toward the
ciliary body, the membrane (which so far has appeared as a single mem-
brane) splits into two lamellae, even before it reaches the or a serrata
retinae; the outer elastic lamella maintains its bow-string course still
farther; the inner cuticular membrane, however, becomes wavy and
separated farther and farther from the elastic lamella as one nears the
end of the retina. At first the space appears empty (by Van Gieson's
stain), then there appears a longitudinally fibrillated collagenous tissue,
which becomes thicker and firmer in the orbiculus ciliaris, and stains
much more intensely red with fuchsin than does the stroma of the vessel
layer. Here and there, the interlamellar tissue contains elongated


nuclei, but no blood-vessels. In surface view, the wavy fibrillae show
a meridional course, as is well depicted by Henle (94).

Sattler (187) found a special capillary system in the posterior part
of the ciliary body and the most anterior portion of the chorioidea;
this consists of narrow capillaries and lies inside the choriocapillaris.
It can, therefore, be suspected that this second capillary system has its
seat in the interlamellar connective tissue. Since Sattler himself found
it in only half of the eyes, it may well be only an abnormality; I have
found such capillaries in only a few otherwise normal eyes.

Upon the cessation of the elastic lamella, the interlamellar connective
tissue merges with the vessel layer.


(Glass membrane of the ciliary body of the older authors, outer

glass membrane of the pars ciliaris retinae, 184)

(PL VII, 4, 5, Cu)

This is a continuation of the lamella of the same name in the chorioidea
and is of the same structure as it; it covers the whole uveal portion of
the ciliary body as far as the neighborhood of the iris root. It is, in
general, very thin, and possesses a greater thickness only in the anterior
third of the ciliary processes, where it attains the thickness of Descemet's
membrane in older persons (PL VIII, n, Cu). In this location it is,
moreover, easiest demonstrable, especially by Van Gieson's stain; the
weakly red-colored membrane then stands out plainly from the brilliant
red sclerosed connective tissue of the vessel layer.

Yet Wolf rum (240) is of the opinion that the clearer layer described is only hyalin-
ized connective tissue, and that the cuticulum proper is here as thin as in the orbiculus

The difficulty of seeing the cuticular lamella in the other parts of the
ciliary body is much less due to the thinness of the membrane than it is to
the numerous uneven areas on the inner surface of the ciliary body; these
are formed in part by its union with the interlamellar connective tissue.
The irregularities consist of ridges of varying height and size; they show
many horn-like branchings and often run together into a closed network,
so that the inner surface of the ciliary body has a honeycombed appear-
ance. Heinrich Mueller (156) first accurately described this structure
and it is called the reticulum of Heinrich Mueller after him.

Surface preparations are absolutely necessary for the study of the reticulum;
only in this way does the network come out properly and one who has once seen such a
surface preparation will never have the idea that the reticulum is brought about by
a wrinkling of the inner surface from the contraction of the ciliary muscle.


For making such a preparation cadaver-eyes are best; the epithelial covering
of the ciliary body is then more easily detached from the cuticular lamella, for the
cadaverous degeneration only destroys the protoplasmic parts and leaves the more
resistant glass membranes unchanged. The retina is bluntly detached at the ora
serrata, the pigment epithelium and all of the layers lying inside then comes away
with it, and if a few remnants of pigment remain behind in the deeper meshes it does
not interfere with the recognition of the reticulum. One then turns the preparation
over and deftly removes the ciliary muscle and the vessel layer. The inner surface
side is then laid up and the preparation is mounted in glycerin or stained with Mallory's
hematoxylin and mounted in Canada balsam.

In this way one gets a general view of the whole orbiculus ciliaris. The corona,
alone, does not permit the making of such a preparation, because the folding of the
surface is too marked; this zone is better studied in sections.

In general, three varieties of the reticulum with respect to height of
ridges and width of meshes can be made out; naturally, these are not
sharply separated from one another.

1. The larger meshes (PI. VII, 4) are rounded or polygonal, and have
a width of 40 to 50 mu and a depth of as much as 40 mu; the ridges (/)
are thick and high, often thickened at the free border and finely striated
on the surface.

2. The small meshes (PL VII, 3, 5) have only about one-half or
one-third the diameter of the large meshes and are very much more
irregular; the ridges are low and narrow.

3. Among these appear ridges characterized by special thickness,
height, and striation; in general, they have a meridional course; the
immediately adjacent meshes are, therefore, very deep. These high ridges
go over into low and narrow ridges at the sides and ends, and the whole
figure thereby takes on a branched appearance or has similarity to a bone
corpuscle (PI. VII, 3; the darkest portion of the reticulum).

The reticulum extends over nearly the entire inner surface of the ciliary
body, although a narrow strip in front of the ora serrata and the ridges
of the ciliary processes are practically free from it.

Starting in front of the ora serrata one usually encounters large meshes
right where the reticulum as a whole begins. Not infrequently they are
closed off into a girdle, which is then visible even with a loupe, and copy
the form of the ora serrata (cf. p. 108).

Furthermore, the striae ciliares are sometimes formed by several rows
of large meshes. The small meshes, or a zone with an indistinct reticulum,
follow immediately upon the large meshes in front. In any case the
small meshes are encountered in the fore part of the orbiculus as a closed
zone, and in this are the high and thick, bone-corpuscle-like ridges (PI.
VII, 3).


The reticulum again becomes less plain over the corona ciliaris, in
particular in the ciliary valleys in front, inward along the sides of the
processes, and disappears, as above stated, over the ridges of the ciliary
processes, i.e., in so far as they show a lighter color, or is reduced to
wholly insignificant irregularities.

On section the reticulum appears only as an angular contour when
weakly developed something like the silhouette of a far-off mountain
chain. When well developed, however, narrow projections stand out,
bordered by parallel smooth sides with rounded edges, or (in the larger
ridges) often ending with a thickened rolling margin. The height of the
ridges varies much (PL VII, 4) ; as a rule, the heavier ridges are also the
higher. The inner surface of the orbiculus also takes on a slight uneven-
ness from the varying development of the reticulum. In this way a
closed large-meshed zone forms an even, wall-like thickening; the striae
ciliaris, likewise, stand out somewhat above the level of the remainder of
the inner surface, and the bone-corpuscle-like ridges behind the corona
ciliaris form correspondingly elongated hummocks.

The thin ridges (PI. VII, 5) often consist of only the cuticular lamella;
the thicker ones, however, contain a connective tissue arising from the
layer at the base of the interlamellar connective tissue (PL VII, 4);
it is this which lends the reported striation to the surface view. The
layers of the ciliary body lying farther outward take no part in the forma-
tion of the reticulum; the elastic lamella, in particular, courses smoothly
beneath the ridges.

b) The Epithelial Covering of the Ciliary Body
(Pars ciliaris retinae of the authors)


(PL VII, 2, 4, 5, P}

This is the direct continuation of the pigment epithelium of the
chorioidea and, like this, consists of a single layer of pigmented epithelial
cells. Only in so far as this layer is compelled to lie in the deepenings
of the reticulum, does there come about a heaping up of cells and this is
without loss of the principle of a single layer. The inner ends (the heads)
of the cells show a straight border, the pigment processes characteristic of
the chorioidal pigment epithelium are absent; colorless cement ridges
are not visible in the pigment epithelium of the ciliary body; the cell
borders, like the cell muscles, can only be seen in bleached sections. The
pigment consists of larger darker granules, which are throughout rounded;


therefore, the pigment epithelium of the ciliary body as a whole appears
darker and blacker than does that of the chorioidea.

The form of the cells changes in various parts of the ciliary body.
Where the inner surface is smooth, as just in front of the ora serrata, the
cells are short and cylindrical, some 6 mu broad and 18 to 23 mu high;
the nucleus is oval and placed with the long axis at right angles to the
inner surface of the ciliary body. The large meshes of the reticulum are
filled out by pigment (PI. VII, 4), the cell layer as a whole goes down
into the depression, and its cells take on an irregular polyhedral form.
These evaginations of the pigment epithelium do not possess a lumen, only
a funnel-form depression on the inner surface of the pigment epithelium.
The layer as a whole undergoes an appreciable thickening by these
evaginations (as much as 60 to 80 mu) and seems just so much darker on
the surface view than do the smooth portions (darker girdle in front of the
ora serrata and the striae ciliares).

The small meshes (PL VII, 5) are too narrow for the pigment
epithelium to lie in them as a layer; they are, therefore, only filled out
by correspondingly displaced cells, and here one often sees the base of the
cell, i.e., the side of it turned toward the uveal portion, free from pigment
granules. The pigment epithelium over the ridges of the ciliary processes
becomes significantly lower (PL VIII, 1 1, P] (height of the cell 10 to 15 mu),
the cells come to have more breadth than height, and the nuclei stand
obliquely. The pigmentation, likewise, decreases appreciably, so that
one can recognize borders and nuclei - even without depigmentation
(PL VII, 2). This explains the whitish color of the ciliary ridges.

The union between the individual pigment epithelial cells is possibly
no more firm than it is in the territory of the chorioidea. But the
reticulum brings about a considerable increase of the surface and effects
a firmer fixation (anchoring) of the pigment epithelium by means of its
many projections. As a matter of fact, the pigment epithelium cannot
be removed wholly intact, even in a macerated eye; pigment remnants
remain behind, especially in the large meshes.

The outer surface of the pigment epithelium everywhere forms a perfect
mould of the inner surface of the cuticular lamella. This is best seen in
sections of cadaver-eyes in which even a desquamation of the epithelium
has begun. Over the crests of the ridges, too, the epithelium stands
away and the ridges of the reticulum never reach through the entire thick-
ness of the pigment epithelium; it never comes in contact with the next
layer, the ciliary epithelium.

Aside from the evaginations of the pigment epithelium brought about
by the reticulum, there are other evaginations very similar to those of


genuine glands. These are the flask-form epithelial plugs engirt by the
cuticular element lamellae which pass through the interlamellar con-
nective tissue and the elastic lamellae and with their thickened ends reach
as far as the vessel layers. A lumen is not, however, demonstrable in
these structures; they therefore lack an essential morphologic element of a
gland. Such "glands" are found in the anterior part of the orbiculus
especially, but even here only scatteringly.

Whether or not one should consider these structures glands, as does Treacher Collins
(226), seems to me to be a matter of no importance. There is no doubt that the ciliary
body secretes the aqueous, but we have no warrant that this function is reserved for
the reported "glands" and that the rest of the inner surface of the ciliary body takes
no part therein.

(PL VII, 2, 4, 5, CE)

This also forms a simple smooth layer of cells, aside from several folds
in the anterior part of the orbiculus. The protoplasm of these cells is,
in general, free from pigment; pigment is found in the ciliary epithelium
only anteriorly in the neighborhood of the iris root.

This layer corresponds to the entire retina sensu strictiori, with the
exception of the membrana limitans interna; one can convince himself of
this best in the eye of the newborn, where the transition of the retina into
ciliary epithelium is still a wholly gradual one (PL IX, i). Its union
with the pigment epithelium is a great deal more firm in any case than is
that of the retina with the pigment epithelium of the chorioidea, for arti-
ficial and post-mortal detachment stop at the border of the retina. This
union is apparently effected by a cement substance like that uniting the
individual ciliary epithelial cells to one another; but I cannot make out a
special membrane corresponding to a continuation of the membrana
limitans externa. Not infrequently one sees small vacuoles between the
pigment epithelial cells and ciliary epithelium in cadaver-eyes, and here
the points in which they are united are drawn out into pedicles.

The form of the cells varies from that of a cylinder to a cube, and, in
general, their height increases from behind forward.

Immediately in front of the overhanging border of the retina, some
particularly long-drawn-out fiber-like cells appear, as reported on p. 86;
otherwise the cells in the most posterior parts of the orbiculus are 6 to
9 mu broad, and some 30 mu high, therefore markedly cylindrical.
The elongated nuclei lie nearer the outer ends of the cells. Although
most of the cells are straight or inclined slightly forward, or bowed,
small groups of cells show a distinct bend backward. A peculiar crossing


of the cells arises in this way, a microscopic chiasma, so to speak (drawn
by von Ebner, 120). When a closed large-mesh zone is formed in the
reticulum of H. Mueller, the cells in this zone are still higher (40 to 60 mu)
and the roll is thereby heightened.

The inner ends of the cells show a form varying much with the direc-
tion of the cells; the inner surface of the whole layer is not always smooth,
and frequently shows irregular, tooth-like projections (PL VII, 4).
According to Addario (3), the inner ends of the cells go over into finely
striated granular, pointed processes, 2 to 3 times as long as the cell itself,
and broaden out upon the inner surface of the ciliary epithelium, partly
in the direction of the corona, partly toward the ora serrata.

The union between the cells here is, moreover, often a loose one;
clefts and vesicular spaces are found between the cells, especially in those
eyes which show cystoid degeneration of the retina. This spacing up of
the ciliary epithelium is apparently analogous to the so-called degeneration
of the retina.

Even in the anterior parts of the orbiculus the cells are still cylindrical,
although much lower than in the posterior parts, and very unequal in
height, for ridges of the membrana limitans internet ciliaris (cf. p. 124)
are found here and the cells sink down in between them. These ridges
occasion irregularities of the ciliary epithelium, because of their increased
thickness, especially in the eyes of older persons; indeed, it may come
about that the epithelium between two ridges is actually folded (PI.
VII, 5).

When one studies such eyes in meridional section, the ridges come out
less plainly; on the other hand, the irregularities of the ciliary epithelium
are more difficult to understand : the cell borders disappear for a distance
(longitudinal section of a ridge), then the ciliary epithelial cells are piled
up on top of each other for a stretch (longitudinal section of a fold). Only
transverse sections of the orbiculus give us a clear picture.

Over the crests of the ciliary processes the cells are cubical (12 to
15 mu broad, 10 to 15 mu high), and the nuclei are rounded (PL VIII,
ii ; the less pigmented cells).

As one follows the ciliary epithelium still farther toward the iris root,
some pigment appears even in the anterior part of the ciliary processes,
first in the portion lying outside of the nucleus. The protoplasm itself does
not stain at all in this portion ; the pigment granules are much scattered.
At the same time, this pigmentation is sufficient to make the anterior
declivity of the ciliary crests appear notably darker than the posterior part
(PL IV, 10). In the neighborhood of the iris root the pigmentation


rapidly increases and an enlargement of the cells takes place at the same
time (PI. VIII, n).

The so-far unpigmented ciliary epithelium thus undergoes a transi-

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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 14 of 27)