アフガンナキウサギ, Ochotona rufescens rufescens の歯の形態学的および組織学的観察

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The morphological and histological characteristic of the teeth of the Afghan pika, Ochotona rufescens rufescence were studied in 12 animals, weighing about 200-300 grams. After the skulls were soft X-rayed, some were prepared for examination on a dissecting microscope and the others for non-decalcified or calcified sections. The main results obtained were summarized as follows. 1. All of the incisors and molars were rootless. 2. The labial and distal surface of the outer incisors were covered with enamel. On the other hand, it was absent on the palatal and mesial surface. For the inner incisors, the four surfaces were covered perfectly with enamel. 3. Enamel was absent on the buccal surface of the upper molars and on the lingal surface of the lower molars. 4. The longitudinal groove found in the labial surface of the outer incisors was filled comparatively thickly with cellular cementum. In the molars, except the lower M_3, bonelike cementum was supplemented along the longitudinal grooves of each lobule (the isthmus) and reinforced the connection between the two. 5. In both the incisors and molars, all of their surfaces including the filling cementum were covered with remarkably thin acellular cementum. 6. The ameloblast being in the process of forming young enamel derived from the enamel organ in the basal end were degenerated gradually toward the occlusal side and were replaced suddenly with the cementoblasts derived from the dental sac. Consequently, on the region cementum covered over enamel (on the occlusal side). Where enamel was absent, neither ameloblast nor inner enamel epithelium was observed. Instead, only short cementoblasts were seen. 7. As compared with the domestic rabbit, the following differences were pointed out. a. The upper M_3 was absent in this animal. b. The lower M_3 of the animal were of single lobule, while those of the rabbit were of double lobi. c. Distribution of enamel in the mesial and distal surfaces of the outer incisors differed slightly between the two animals. d. The region lacking the molar's enamel in the pika tended to be a very little wider than that of the rabbit.
1986-10-25

アフガンナキウサギ, Ochotona rufescens rufescens の歯の形態学的および組織学的観察

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