360
G. V. LOPASHOV AND O. G.
STROEVA
cultivated on the chorioallantois. After 4-5 days the skin epithelium
assumed the appearance of the corneal epithelium, and the Bowman's
membrane of the cornea was formed under it. At the site where the
epithelium was separated from substantia propria by the mesenchyme
it was underlain by the usual basement membrane, and the fibrils in the
corneal stroma were poorly developed. In other sites they were developed the stronger, the closer was the contact between the epithelium
and the stroma (Neyfakh, 1952d). This experiment demonstrates not
only the influence of the epithelium on the differentiation of the substantia propria, but the reverse relation as well, namely, that the
influence of the latter determines the character of the ectodermal
epithelium in contact with it. The formation of Bowman's membrane
proceeds only where the ectodermal epithelium and the connective tissue
portion of the cornea interact. The influence of the corneal epithelium
on the differentiation of collagenous fibrils is also proved biochemically:
upon the removal of the corneal epithelium, collagen synthesis by
mesenchymal cells of the cornea in 9-10 day old chick decreases 5-6
times reaching the level of collagen synthesis in the sclera. With the
invasion of mesenchyme cells from the region of the sclera into the postepithelial layer of the corneal rudiment, the direction of the mucopolysaccharide synthesis in them also undergoes changes: instead of the
chondroitinsulfuric acid (characteristic of the sclera) the production of
keratosulphate starts (Herrmann, 1958).
The formation of primary argyrophylic fibrils proceeds in the direction of the tension lines of the forming cornea. With an alteration of the
direction of tension during cultivation on the chorioallantois, the fibrils
may be formed even perpendicularly to the anterior epithelium (Neyfakh, 1952a, 1952c). A reorganization of fibril direction proceeds in the
same way in an almost completely formed cornea (at the age of 13 days),
when it develops in a rolled up state (Neyfakh, 1952c). When the intraocular pressure is artificially eliminated during 4-5 days of incubation,
the cornea is considerably thickened due to additional layers of the
stroma and Bowman's membrane. In the system of the whole eye,
however, its histological structure remains undestroyed (Coulombre,
1957). Finally, the formation of the Descemet's epithelium and, correspondingly, of Descemet's membrane, is always related to the presence
of a cavity under the cornea. A Descemet's epithelium already formed
disintegrates to individual mesenchyme cells if the cavity under it
disappears (Neyfakh, 1952a).
The opaque embryonic cornea of a chick embryo begins to transmit
light after the 14th day of incubation and becomes completely transparent by the time of hatching. With the increase of transparency
between the 14th and 19th days the water loss by the cornea progres-
G. V. LOPASHOV AND O. G.
STROEVA
cultivated on the chorioallantois. After 4-5 days the skin epithelium
assumed the appearance of the corneal epithelium, and the Bowman's
membrane of the cornea was formed under it. At the site where the
epithelium was separated from substantia propria by the mesenchyme
it was underlain by the usual basement membrane, and the fibrils in the
corneal stroma were poorly developed. In other sites they were developed the stronger, the closer was the contact between the epithelium
and the stroma (Neyfakh, 1952d). This experiment demonstrates not
only the influence of the epithelium on the differentiation of the substantia propria, but the reverse relation as well, namely, that the
influence of the latter determines the character of the ectodermal
epithelium in contact with it. The formation of Bowman's membrane
proceeds only where the ectodermal epithelium and the connective tissue
portion of the cornea interact. The influence of the corneal epithelium
on the differentiation of collagenous fibrils is also proved biochemically:
upon the removal of the corneal epithelium, collagen synthesis by
mesenchymal cells of the cornea in 9-10 day old chick decreases 5-6
times reaching the level of collagen synthesis in the sclera. With the
invasion of mesenchyme cells from the region of the sclera into the postepithelial layer of the corneal rudiment, the direction of the mucopolysaccharide synthesis in them also undergoes changes: instead of the
chondroitinsulfuric acid (characteristic of the sclera) the production of
keratosulphate starts (Herrmann, 1958).
The formation of primary argyrophylic fibrils proceeds in the direction of the tension lines of the forming cornea. With an alteration of the
direction of tension during cultivation on the chorioallantois, the fibrils
may be formed even perpendicularly to the anterior epithelium (Neyfakh, 1952a, 1952c). A reorganization of fibril direction proceeds in the
same way in an almost completely formed cornea (at the age of 13 days),
when it develops in a rolled up state (Neyfakh, 1952c). When the intraocular pressure is artificially eliminated during 4-5 days of incubation,
the cornea is considerably thickened due to additional layers of the
stroma and Bowman's membrane. In the system of the whole eye,
however, its histological structure remains undestroyed (Coulombre,
1957). Finally, the formation of the Descemet's epithelium and, correspondingly, of Descemet's membrane, is always related to the presence
of a cavity under the cornea. A Descemet's epithelium already formed
disintegrates to individual mesenchyme cells if the cavity under it
disappears (Neyfakh, 1952a).
The opaque embryonic cornea of a chick embryo begins to transmit
light after the 14th day of incubation and becomes completely transparent by the time of hatching. With the increase of transparency
between the 14th and 19th days the water loss by the cornea progres-