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Deciduous tooth germs were removed from the anterior region of human fetuses between 13-16 weeks of age and fixed in glutaraldehyde. Some were post fixed in osmium tetroxide whilst others were block stained with silver nitrate and prepared for electron microscopy. Thick Araldite embedded sections were cut at 1 pm and stained in various ways for examination by light microscopy. Thin sections of bulk silver stained material were examined with the electron microscope before and after staining with heavy metals. Fibers lying between the developing odontoblasts were demonstrable under the light microscope and their appearance was consistent with the classical description of von KorfF fibers. With the electron microscope bundles of collagen fibers up to 1 pm in diameter were present between newly differentiated odontoblasts. Heavy metal staining of sections from bulk silver impregnated material revealed that silver deposition was associated mainly with collagen fibrils. It is concluded that in the crown of human developing teeth, bundles of collagen fibrils are present between the newly differentiated odontoblasts and that these bundles represent those usually described as von Korff fibers.Similar results were found using material from developing molar teeth of mice.Studies of mantle dentine of the developing tooth have included descriptions at the light microscope level of prominent argyrophilic fibers coursing between the odontoblasts and terminating in the region of the basement membrane separating these cells from the internal enamel epithelium. The earliest descriptions of these fibers by Raschkow (1835) and Hansen (1899) were amplified by von Korff ('05) whose name has usually been applied to these structures since that time. Although there has been discussion regarding the presence of von Korff fibers in later formed dentine (Lester and Boyde, '68) their demonstration in forming mantle dentine using appropriate staining methods and light microscopy is in no doubt (Symons, '56). With the electron microscope Masukawa ('59) illustrated a zone of "gnarled" collagen fibrils parallel to the odontoblastic processes which might correspond to von KorfF fibers. Scott and Nylen ('60) in a description of the electron microscopic features of dentinogenesis distinguished between mantle dentine and circumpulpal ANAT. REC., 174: 175-190. dentine. They stated that in mantle dentine there is a fan like arrangement of coarse collagen fibrils which they designated as the terminations of von Korffs fibers, while in circumpulpal dentine the matrix was composed of considerably finer fibrils arranged in the form of a network. Noble, Carmicheal and Rankine ('62) demonstrated what they regarded as von Korf€ fibers in the area of the sheath of Hertwig using human material while Johansen and Parks ('62) and later Bevelander and Nakahara ('66) described collagen bundles up to 0.5 pm in thickness between newly formed odontoblasts. Reith ('68) confumed the views of Scott and Nylen ('60) and described the association of von Korff fiber...

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