VIII.
MORPHOGENESIS OF THE VERTEBRATE EYE
359
The cornea was transparent even when this operation was performed
on newborn rats; the lids above the operated eye in the latter remained
closed. A complete reduction of the vitreous chamber took place in the
operated eyes, while the large anterior chamber was preserved (Stroeva,
1956b). Thus, in adult terrestrial Vertebrates, unlike amphibian larvae
and adult demersal fish, the cornea is a very stable formation, while the
eye looses its ability to induce cornea in the embryonic skin.
All the investigations on corneal induction in Amphibians are covered
by the range of problems presented above, while those on the chick add
a new chapter to the study of corneal development. During corneal
induction, the specific influence of the eye is necessary only for the
formation under the epithelium of a cell-free postepithelial layer, the
rudiment of the substantia propria (Neyfakh, 1952a). Formation of
Descemet's epithelium, invasion of mesenchyme cells and the differentiation of the fibrils of the stroma proceed in the absence of the eye,
when isolated corneae of various ages are cultivated on the chorioallantois (Neyfakh, 1952c). When only the central part of the cornea was left
on the eye (at the age of 4 days), while the surrounding surface epithelium and the mesenchyme were removed, the cornea rolled up with
the epithelium inwards, and the postepithelial cell-free layer surrounded
it on all sides. After 4-6 days of cultivation on the chorioallantois, the
postepithelial layer became considerably thicker on the side facing the
eye, while on the opposite site its thickness was as before. This shows the
postepithelial layer to be formed by the anterior corneal epithelium
under the influence of the eye (Neyfakh, 1952d). No fibres can be found
in it even after silver impregnation. During the time of cultivation the
capacity of the postepithelial layer to be evenly stained from all sides
with anilin blue strongly increases. This proves the independence of this
process both of the influence of the eye and of the presence of the
mesenchyme (Neyfakh, 1952d). In an analogous experiment, where the
surface epidermis was left around the cornea, and where mesenchymal
cells invaded the postepithelial layer of the cornea prior to its rolling up,
many fibrils were present. Thus the formation of fibres in the substantia
propria proceeds only in the presence of mesenchymal cells. At the same
time the intensity of fibril formation in the stroma is determined by its
interaction with both corneal epithelia. In internal corneal layers which
become considerably thicker when cultivated on the chorioallantois, the
formation of fibrils is delayed, while an intensive fibril formation is
observed near the anterior corneal and Descement's epithelia (Neyfakh,
1952a). The same correlation was observed in another experiment. A
corneal area (at the age of 8-9 days) devoid of anterior corneal epithelium was placed between the epithelium and the connective tissue
layer of the skin in a 4 days old embryo. The whole 'sandwich' was
MORPHOGENESIS OF THE VERTEBRATE EYE
359
The cornea was transparent even when this operation was performed
on newborn rats; the lids above the operated eye in the latter remained
closed. A complete reduction of the vitreous chamber took place in the
operated eyes, while the large anterior chamber was preserved (Stroeva,
1956b). Thus, in adult terrestrial Vertebrates, unlike amphibian larvae
and adult demersal fish, the cornea is a very stable formation, while the
eye looses its ability to induce cornea in the embryonic skin.
All the investigations on corneal induction in Amphibians are covered
by the range of problems presented above, while those on the chick add
a new chapter to the study of corneal development. During corneal
induction, the specific influence of the eye is necessary only for the
formation under the epithelium of a cell-free postepithelial layer, the
rudiment of the substantia propria (Neyfakh, 1952a). Formation of
Descemet's epithelium, invasion of mesenchyme cells and the differentiation of the fibrils of the stroma proceed in the absence of the eye,
when isolated corneae of various ages are cultivated on the chorioallantois (Neyfakh, 1952c). When only the central part of the cornea was left
on the eye (at the age of 4 days), while the surrounding surface epithelium and the mesenchyme were removed, the cornea rolled up with
the epithelium inwards, and the postepithelial cell-free layer surrounded
it on all sides. After 4-6 days of cultivation on the chorioallantois, the
postepithelial layer became considerably thicker on the side facing the
eye, while on the opposite site its thickness was as before. This shows the
postepithelial layer to be formed by the anterior corneal epithelium
under the influence of the eye (Neyfakh, 1952d). No fibres can be found
in it even after silver impregnation. During the time of cultivation the
capacity of the postepithelial layer to be evenly stained from all sides
with anilin blue strongly increases. This proves the independence of this
process both of the influence of the eye and of the presence of the
mesenchyme (Neyfakh, 1952d). In an analogous experiment, where the
surface epidermis was left around the cornea, and where mesenchymal
cells invaded the postepithelial layer of the cornea prior to its rolling up,
many fibrils were present. Thus the formation of fibres in the substantia
propria proceeds only in the presence of mesenchymal cells. At the same
time the intensity of fibril formation in the stroma is determined by its
interaction with both corneal epithelia. In internal corneal layers which
become considerably thicker when cultivated on the chorioallantois, the
formation of fibrils is delayed, while an intensive fibril formation is
observed near the anterior corneal and Descement's epithelia (Neyfakh,
1952a). The same correlation was observed in another experiment. A
corneal area (at the age of 8-9 days) devoid of anterior corneal epithelium was placed between the epithelium and the connective tissue
layer of the skin in a 4 days old embryo. The whole 'sandwich' was