Development of cleavage line patterns in the skin of the ovine fetus

In fifty six ovine fetuses of both sexes, ranging in length from 20 mm to 41 cm crown-rump length, the developmental features of the cleavage lines of the skin over the whole body were examined by the stab-wound method using a metal probe with a sharp conical point. 1). Cleavage lines were observed as early as the 20 mm fetal stage. During each fetal stage, the various regions and areas of the ovine body were represented by individual cleavage line patterns. 2). The cleavage line patterns changed as the occurred the various structures elongated or thickened during fetal growth. 3). Among the fetuses, similar cleavage line patterns recurred in particular regions or areas, e.g., the flank, the antebrachium, the crus and fore- and hind-digits. 4). This recurrence of cleavage line patterns reflected the alterations with occurred with the growth of the whole body, in accord with the so-called functional-morphological rhythm of development.