PROBLEMS IN CORNEAL MORPHOGENESIS
99
of fiber matrix the tensile strength is probably equal in all directions in
the plane of the cornea, and consequently the shape of the cornea is
maintained.
V. The Posterior Epithelium
The posterior epithelium of the cornea (often referred to as the
endothelium or the mesothelium ofDescemet) is almost universally agreed
to be of mesodermal origin (see Redslob, 1935; Stocker, 1953; Streeter,
1951). The cells migrate in from the limbic mesenchyme along the
posterior face of the postepithelial layer or the directional membrane
(Knape, 1909; O'Rahilly and Meyer, 1959). Sondermann (1930, 1949)
seems to be unique in claiming at least a partial origin of the posterior
epithelial cells from the ectoderm. The posterior epithelium is a simple
low cuboidal sheet of cells from the outset. I t always appears to migrate
into position before the limbic mesenchyme begins to invade the postepithelial layer (Laguesse, 1926; Hagedoorn, 1928; Seefelder and Wolfrum, 1906). The cells which constitute the posterior epithelium continue to divide to allow for its increase in area (von Sallmann et'al:,
1961). However, while mitosis continues for a considerable period following birth, it eventually comes to a halt (Ballowitz, 1900; Cogan,
1951; Mills and Donn, 1960; Binder and Binder, 1957; Nagano, 1914;
von Sallmann, 1960). Wounding of the posterior epithelium very quickly
evokes mitotic activity in the region of the wound, and the defect is
repaired (Binder and Binder, 1957 ; Mills and Donn, 1960 ; von Sallmann
et ah, 1961).
The cytologie appearance of mature posterior epithelial cells is
described by Jakus (1961) and by Kaye and Pappas (1962). Aside from
the role it probably plays in the deposition of Descemet's membrane,
the posterior epithelium also functions importantly in keeping the
stroma deturgesced. While the anterior epithelium also appears to be
involved in this process, the posterior epithelium plays by far the more
important role (Harris, 1957).
V I . Descemet's Membrane
There is a general concensus that the membrane of Descemet originates from, or at least under the influence of, the posterior epithelium.
I t arises relatively late. In the chick embryo Jakus (1956) traced its
origin from the 10th day of incubation when it appeared as isolated pads
of material situated between the posterior epithelium and the posterior
surface of the stroma. Subsequently these pads enlarged laterally as well
as in thickness and fused to form Descemet's membrane. In an excellent
comparative study Jakus (1956) deciphered the structure of this mem-
99
of fiber matrix the tensile strength is probably equal in all directions in
the plane of the cornea, and consequently the shape of the cornea is
maintained.
V. The Posterior Epithelium
The posterior epithelium of the cornea (often referred to as the
endothelium or the mesothelium ofDescemet) is almost universally agreed
to be of mesodermal origin (see Redslob, 1935; Stocker, 1953; Streeter,
1951). The cells migrate in from the limbic mesenchyme along the
posterior face of the postepithelial layer or the directional membrane
(Knape, 1909; O'Rahilly and Meyer, 1959). Sondermann (1930, 1949)
seems to be unique in claiming at least a partial origin of the posterior
epithelial cells from the ectoderm. The posterior epithelium is a simple
low cuboidal sheet of cells from the outset. I t always appears to migrate
into position before the limbic mesenchyme begins to invade the postepithelial layer (Laguesse, 1926; Hagedoorn, 1928; Seefelder and Wolfrum, 1906). The cells which constitute the posterior epithelium continue to divide to allow for its increase in area (von Sallmann et'al:,
1961). However, while mitosis continues for a considerable period following birth, it eventually comes to a halt (Ballowitz, 1900; Cogan,
1951; Mills and Donn, 1960; Binder and Binder, 1957; Nagano, 1914;
von Sallmann, 1960). Wounding of the posterior epithelium very quickly
evokes mitotic activity in the region of the wound, and the defect is
repaired (Binder and Binder, 1957 ; Mills and Donn, 1960 ; von Sallmann
et ah, 1961).
The cytologie appearance of mature posterior epithelial cells is
described by Jakus (1961) and by Kaye and Pappas (1962). Aside from
the role it probably plays in the deposition of Descemet's membrane,
the posterior epithelium also functions importantly in keeping the
stroma deturgesced. While the anterior epithelium also appears to be
involved in this process, the posterior epithelium plays by far the more
important role (Harris, 1957).
V I . Descemet's Membrane
There is a general concensus that the membrane of Descemet originates from, or at least under the influence of, the posterior epithelium.
I t arises relatively late. In the chick embryo Jakus (1956) traced its
origin from the 10th day of incubation when it appeared as isolated pads
of material situated between the posterior epithelium and the posterior
surface of the stroma. Subsequently these pads enlarged laterally as well
as in thickness and fused to form Descemet's membrane. In an excellent
comparative study Jakus (1956) deciphered the structure of this mem-