Pair Of Parallel Lines Research Articles

Ultrastructure of retinal capillaries of the rat

The retinal capillaries of normal, albino rats were studied with the electron microscope. The capillaries are lined by flat endothelial cells which rest upon a homogeneous basement membrane. Mitochondria were rare. Spherical vesicles, referred to as pinooytic vesicles by some authors, were found distributed throughout the endothelial cytoplasm but more often aligned along the free border of the cell. In addition to the vesicles, fine structures, appearing as discontinuous pairs of parallel lines and interpreted as portions of endoplasmic reticulum, were also dispersed in the endothelial cytoplasm. Microvilli of various lengths projected from the endothelial cytoplasm into the lumen of the capillaries. There was considerable variation in the width of the basement membrane which encircles the endothelial layer of the vessel. Pericytes were embedded in the basement membrane and lay in a plane parallel to the longitudinal axis of the capillary. Although the capillaries were not, as a rule, completely surrounded by pericytes, the latter cells were often superimposed upon one another, adding significantly to the over-all thickness of the capillary. In all specimens examined, the capillaries were invested by glial elements of the retina. There was no contiguity of capillary and neuronal tissue.

The Influence of Condenser Aperture on the Resolution of a Pair of Parallel Lines

An expression is found for the distribution of light in the image of two parallel lines which are illuminated by a condenser of numerical aperture equal to σ times that of the imaging objective. The intensity distributions are plotted for various values of σ and of the separation of the lines. The resolving power of the system is written ξ=Kλ/N.A. and K is plotted as a function of σ.

Modified Method of Fizeau Fringes for Thickness Measurements*

The exit slit of a monochromator is focused upon a pinhole located in the first focal plane of an objective utilized for viewing the multiple-beam fringes formed by inter-reflections between two inclined surfaces, one of which is stepped. The step is focused into the plane of an eyepiece whose reticule contains a pair of parallel lines between which successive fringes are set and measured by rotation of the wavelength drum. The preferred, and possibly novel, method of interpreting the observations is discussed.