This is the first case report of abnormal pigmentation (darkening) of the human peripheral nerve. Gross anatomically, only the posterior cutaneous nerve of thigh showed abnormality bilaterally. Light microscopical examinations showed that the pigmentation was localized in the perineurial epithelial sheath and endoneurial vessels. The pigmented loci were hematoxylinophilic, PAS positive, Schmorl positive, Masson-Fontana negative, Puts negative, diazo negative, and showed neither autofluorescence nor birefringence, denying the presence of melanin, hemosiderin, lipofuscin, and any other well known pigments. All of the pigmented loci and many other non-pigmented areas in histological sections were von Kossa positive indicating the presence of calcium. Electron microscopy and microanalysis showed that calcium apatite crystallites occurred in and adjacent to the perineural epithelium, the endothelium of endoneurial vessels, the axoplasm and Schwann cells. The crystallites appeared originating intracellularly, at places penetrating the cytolemma and projecting toward the interstice of the nerve. Whether a portion of nerve fasciculus appears pigmented or not was directly correlated with the presence or absence of extracellularly projecting calcium crystallites. It was assumed that an unknown kind of pigment accumulated on the extracellularly projecting calcium deposits, but not on those deposits being confined intracellularly.

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The superficial structure of the tongue for the Mongolian gerbil, Meriones unguiculatus, were observed by scanning electron microscope. The external characters of tongue and the types of papillae (the filiform, fungiform, vallate and foliate papillae) were fundamentally much the same to other Muridae and Cricetidae. In this animal, the small filiform and the fungiform papillae were observed not only on the dorsal surface of the palatal part, but also on the under surface of the anterior free part where there is no papilla in other rodents. The foliate papillae, furthermore, had well-developed von Ebner glands which opened into the bottom of the furrows. It is considered that these characters point to the adaptation to live in sandy deserts.

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Previous studies have demonstrated that progesterone stimulates rapid and simultaneous biosynthesis of egg-white proteins in the tubular gland cells and in some epithelial cells of the oviduct in oestrogen-primed chicks. The present investigation was undertaken to compare hens with oestrogen-primed chicks, and to identify the precise site of progesterone-induced avidin biosynthesis in the oviduct. Endogenous biotin-binding sites were revealed in secretory granules of tubular gland cells and in epithelial cells. Biotin-binding sites were also observed in the amorphous matrix of the rough endoplasmic reticulum cisternae in the acinar cells of hormone-treated chicks. Immunoreactive avidin was similarly found in secretory granules of tubular gland cells by block-staining methods using anti-avidin (Fab')2antibody. In the present study, the cytochemical localization of the biotin-binding sites and immunogenic avidin was identical with that of progesterone-receptor sites.

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The form in frontal view of the recent human facial skeleton, including the frontal bone, was simulated under the condition of uniform strength to cope with the forces in the chewing action, by using the two-dimensional frame model made of members with step-wise variable cross-sections and by using the finite element analysis method. The simulation, in which the condition was applied to the elements of the model in the frontal bone region, resulted in a form different from the actual facial skeleton But the simulation in which the condition was not applied to the above elements resulted in a form tolerably similar to the actual facial skeleton. Hence, it was concluded that the biomechanical role of the frontal bone was different from that of the facial bones: the former was part of the brain casing and the latter a chewing machine, including the casings of the eyes and the nose, regulated by the law of uniform strength to cope with the forces in the chewing action.

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New glands were observed at the omasal end in 34 goats examined by binocular stereoscopic, light and scanning electron microscopy. They were situated in the submucosa and were classified as compound tubulo-alveolar glands, which consisted of mucous, serous and myoepithelial cells. The myoepithelial cells were found to be of the stellate type by scanning electron microscopy. Morphologically, the glands were considerably similar to the esophageal gland as regards their situation in the mucous membrane and the types of cells forming them.

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Human gonadal development was observed in early embryos by electron microscopy. In 5-week-old embryos, the genital ridge (GR) was forming with a single layered superficial epithelium, which consisted of two types of cells, clear and dark cells. In 6-week-old embryos, the swelling into the coelom of the GR was greatly increased. Primary sex cords (PSCs)were forming as columnar projections from the primitive cortex cells. The basal lamina appeared between the future cortex and medulla, indicating that PSCs are of cortex origin. The primordial germ cells (PGCs) completed their migration into the GR: many of them were incorporated, in PSCs. In 7-8-week-old embryos, the PSCs were well developed, and clear and dark cells were still distinguishable within the PSCs. Sex differentiation in the primitive gonad became discernible on a histologically basis. In the testis, the tunica albuginea appeared and PGCs were being incorporated in the PSCs and were associated with both clear and dark cells. In the ovary, the cortex was dominantly proliferated and in the zone demarcating the cortex and medulla, collagen fibers were observed. In male embryos at 9 weeks onwards, the PGCs located in the PSCs underwent some ultrastructural changes, and the PSCs were branching and their peripheral ends were anastomosing with each other to form the rete testis.

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The epithelium lining the mouse larynx occupied the transitional zone between the keratinized stratified squamous epithelium lining the oral cavity and the ciliated columnar one continuing to the trachea. The epithelium showed gradations ranging from stratified squamous through stratified cuboidal to ciliated stratified low-columnar type. It is suggested that the epithelium is identical with the "intermediate epithelium (Nakano,1986)" in the mouse nasopharynx.

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