生後5日目小猫の下顎に於ける歯髄, 歯根膜, 骨膜, 歯肉及び Serre 氏真珠の知覚神経分布に就て

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  • On the Sensory Nerve Supply of Dental Pulp, Peridental Membrane, Periosteum, Gum and SERRE's Pearl in the Lower Jaw of Five-Day-Old Kitten

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In a 5-day-old kitten, the plexus dentalis originating in the n. alveolaris inferior of the lower jaw was found already very well developed, comprising numerous thick sensory fibres and far less numerous thin vegetative fibres.<br>The rami dentales emerging from this plexus run into the dental pulp of the milk teeth, the number of the nerve fibres increasing abreast with the growth of the teeth. Now, the time these nerve branches enter the dental pulp was found considerably later than was anticipated, for the innervation begins only in the stage where enamel is produced from the enamel organ and dentine from the odontoblasts. Thus, the number of nerve fibres to the dental pulp of the still growing and yet uncut milk tooth is very limited, only a few sensory fibres ending in mere unbranched and simple branched terminations at some distance from the odontoblast layer, no RASCHKOW's plexus being as yet found in formation. No such fibres innervating the odontoblast layer or complex branched terminations in the dental pulp as found in adult animals were found in the mandible of my kitten. The terminal fibres of the existent sensory terminations show little noteworthy change in size or winding in their courses.<br>In my kitten, as found in a 6th month human fetus (SHIRAISHI), besides the milk teeth, immature permanent teeth consisting merely of a cap-shaped dental germ and a dental papilla and somewhat better differentiated permanent teeth were contained in the lower gum. Thick sensory fibres were found entering the rather powerful connective tissue layer covering these buds of permanent teeth and sometimes even the dental germ. These fibres end in unbranched and simple branched terminations with terminal fibres often showing change in size in their courses before ending in sharp points.<br>The peridental membrane between the milk teeth and the alveolar wall is formed in the main of the loose reticular connective tissue forming the dental sac and only in very limited areas by the stout connective tissue as in adult animals. Many nerve fibres from the rami gingivales arising from the plexus dentalis were seen running through this immature peridental membrane toward the propria of the gum while sending out a considerable number of sensory fibres into the membrane in their courses. Their terminations were much simpler than in man and adult dog, simple branched ones forming the majority. Their terminal fibres, however, sometimes show change in size and unusual winding in their courses suggestive of their probable development into very peculiar complex branched terminations as found in adult animals.<br>Some specific sensory terminations were found in the entire area of the young periosteum of the mandible of my kitten, especially, in the alveolar margin. The bone tissue was as yet in the course of growth and the periosteal tissue was still immature, being composed of an outer fibrous connective tissue layer, an osteogenetic layer lining it and an osteoblast layer on the inside. Thick sensory fibres run into this young periosteum accompanying some fine vegetative fibres, and after a repeated ramification end in simple and complex branched terminations. Their terminal fibres often show conspicuous change in size and run into the fibrous layer and further into the osteogenetic layer, even into the osteoblast layer before terminating.<br>In the lower jaw of my newborn cat. I found a small number of SERRE's pearls somewhat smaller in size than those in human fetus. A small number of sensory fibres are found running into these pearls, as in the case with man (SHIRAISHI), forming unbranched or bifurcated terminations therein with terminal fibres showing not much change in size and winding in their courses. The SERRE's organs are presumably so many sensory organs.

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