Abstract
By metallic shadow-casting of specimens for electron-microscopical examination, fibrils a few hundred Angstroms in diameter were demonstrated in cuprammonium and in viscose rayons. Fibrillation was more distinct in the rayons having a high degree of orientation. The fine fibrils in the fibers of both these regenerated celluloses were similar to those previously observed in native cellulose fibers. A comparison of surface replicas of the fibers revealed distinct differences. Whereas the cuprammonium rayon fibers were relatively smooth except for occasional markings which gave them a scaly appearance, the viscose rayon fibers were rougher, and showed an irregular netlike pattern.