Some puzzles in the microscopic structure of the stroma

The mammalian corneal stroma has some intriguing features related to its la mellar structure, Optical Lamination, Stromal sections under the polarizing microscope show birefringent bands that are about 5 times less numerous th an the collagenous lamellae seen in transmission electron microscopy (TEM). Scattered light reveals similar laminae in the intact fresh tissue. Cohesi on Very thin sections of stroma do not fall apart under wader, indicating t he presence of a structural framework that holds the collagen fibrils toget her. Shear Distortion. The stroma shears very readily in its plane; the she ar amplitude increases and then decreases as the tissue hydrates, This sugg ests that the structural framework is coiled at physiological hydration and can expand about 10 Limes. Folding: When the stroma swells, the lamellae a re thrown into waves that lie both in the plane of and perpendicular to its surface. It is difficult to understand how the latter are packed.