STREAK

n. Strek. Lat, stria. Fr.. strie, ligne. Ger., Streif, Streifen, Rinne. A line or stripe, [a. 48.] Abdominal s's. See under Linear ATROPHY of the skin. Germinal s. See Primitive s. Medullary s. See Medullary GROOVE. Primitive s. Lat., nota priinitiva. Fr., ligne primitive (ou axiale). Ger., Primitivstreif, Primitivstreifen, Axenstreifen [His]. Syn.: axial plate, primitive trace. In embryology, a temporary structure consisting of a sickle-shaped opacity (which becomes a strap-like thickening) of the germinal disc of the blastoderm, starting from that side of the disc which afterward becomes the narrow end, and gradually extending to or beyond the centre of the transparent area: a linear or strap-like ma of cells formed by direct proliferation from the lower (inner) cells of the epiblast, constituting the origin of the mesoblast. It is the first indication of the lineaments of the future embryo. Supposed by some writers to be the vestige of a blastopore. [A, 5.] Purkiiije's elliptical light-s's. An appearance seen by Purkinje while looking at a glowing sponge in darkne . When the image of the sponge lay on the inner side of the point of fixation, there appeared two horns running transversely outward from the margin of the illuminating image, with the convexities upward and downward, so as to inclose an ellipse between the object and the entrance of the optic nerve. [Graefe u. Saemisch ().] [s. 547]