Detailed microscopic examination on a total of 31 cases of ameloblastoma was conducted using, as a preliminary step, a number of large-sized tissue sections covering whole body of the tumor, and the possible structural difference due to their localities of origin was carefully investigated between individual tumors occurring respectively in molar teeth and frontal teeth regions of lower jaw and those occurring in upper jaw. Particularly, with tumors occurring in the lower molar region, effort was centered to elucidate possible histological difference existing between segments of individual tumor body constituting its buccal, lingual, mesial, distal, alveolar, and lower marginal sides. Careful study was further extended to the relationship between the tumor and the surrounding tissues, and the findings were comparatively studied with reference to the clinical symptomes. Conclusions obtained are as follows. 1) Difference in the radiologic and patho-histologic findings was found to exist between group of 24 ameloblastomas occurring in lower molar region and group of 7 ameloblastomas occurring in lower frontal teeth region and in upper jaw. 2) Of 24 ameloblastoma occurring in lower molar region relatively large number (15 cases) showed the radiologic picture typical of the tumor, and in about equal number of the tumor segmental difference was detected from patho-histological viewpoint (17 cases). However, in every cases of these tumors, parenchymatous networks had close resemblance to the structure of enamel organ. 3) With all the cases of ameloblastoma occurring in upper jaw and lower frontal teeth region, atypical radiologic picture was observed, and segmental patho-histologic difference was poorly observed. In most of the cases (6 out of 7) the parenchymatous networks showed poor resemblance to the structure of enamel organ. 4) Of those tumors occurring in lower molar region, there was found parallelism of histological findings between the alveolar and lower marginal sides, and between the buccal and lingual sides of a single tumor, and, this permitted clearer presentation of the tumor structure by comparing above two sets of findings. Thus, histologic difference was found to be existing between the two sets of findings in eleven out of 24 cases. Comparison between the mesial and distal sides segments of the tumors revealed difference existing in 10 cases out of the total tumors. It was further noted of the histological difference that tendency to cyst formation was most conspicuous in the distal than in the bucco-lingual segments and least conspicuous in the alveolar and lower marginal segments through the tumors. This difference was also observed in the growth pattern of the tumors, alveolar and lower marginal segments being most infiltrative, the bucco-lingual less infiltrative and the distal segments expansive with well-defined boundary to the surrounding tissues.

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A patho-histological study has been undertaken on full-length tissue sections of a total of 9 cases of odontomas with reference to their respective clinical manifestation. The findings obtained were summarized as follows. 1) All the tumors included in this study were the 'hard-type' odontoma which appeared within the maxilla or mandible independently and with no direct association with erupted dentition. 2) With 6 cases of the odontomas the structure was studied by the roentogen rays three-dimensionally and the number of the tooth anlage and arrangement of the tooth components were respectively examined. Each of the 3 cases of these consisted of two tooth anlages geminated either at the crown or at the root portions of the teeth. In two cases of the odontoma there was seen complex arrangement of the tooth elements in one individual tooth, and in the last case there was seen an aggregation of a large number of teeth. 3) Based on the number of tooth anlage involved in the formation of individual odontoma and on the patterns of arrangement of the tooth components, the 9 cases of odontoma could be classified in the following manner : 1. Inversive constitutional odontoma with single tooth anlage (3 cases) 2. Root-fused odontoma with 2 tooth anlages (2 cases) 3. Composite odontoma with multiple anlages (2 cases) 4. Crown-fused odntoma with 2 tooth anlages (1 case) 5. Complex odontoma with single tooth anlage consisting mainly of cement substance (1 case)

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Various forms of experimental traumatic injuries were exerted on 146 unerupted permanent teeth of 50 dogs aged 50 to 120-days after birth. Following the radiologic observation made on these teeth over the period from 4 to 324 days after the operation, the animals were sacrificed, and the teeth were studied histologically. The findings were summarized as follows : In the first group of animals in which the superficial layer of enamel with incomplete calcification was filed away experimentally, the finding was as follows. The enamel substance lost by the expeirmental injury could never be restored in any way. After the injury the enamel epithelium proliferated in strands or in networks, and in the two cases of teeth examined at 26 and 93 days respectively after the injury formation of small cysts was observed. Thers was, however, no retardation of tooth eruption in this group of teeth. The second group of teeth in which the hard tissues were surgically fractured showed the following picture. The enamel substance lost by the injury could never be restored thereafter. However, in the dentinal layer, apposition of newly formed dentin was observed which started at the fractured surface of the tissue. The tissue regeneration was shown to be generally complete with those teeth which elapsed more than 67 days after the operation. Of eleven cases of teeth observed until to the expected time of eruption, only three were observed to erupt. The third group of teeth in which the total hard tissue of the crown was removed showed the following picture. On the fourth day after the operation there were observed on the surface of the exposed tissue of dental papillae a layer of arranged odontoblasts and progressive formation of the primary dentin-like tissue. In this group of teeth eruption was observed to take place in 4 out of 5 teeth which were kept under observation until to the expected time of eruption. However, the crown portion of the erupted teeth was shown to be imperfectly formed. The fourth group in which the hard tissue of the crown and a part of the adjoining dental papillae were surgically removed, showed the following picture. That is, in the teeth observed 4 to 7 days after the operation there was shown a calcified tissue being formed at the junction between the remaining tissue of the dental papillae and the surrounding mesenchymal tissue. These teeth, however, eventually showed abnormal development and all failed to erupt. The fifth group of teeth in which the superficial layer on the lower margin of dental papillae was scarified, showed the following picture. That is, in those teeth in which the Hertwig, s epithelial sheath suffered the injury there was seen temporary formation of the irregular dentin at the site, which, however, failed to impair the normal course of the tooth development and eruption in any member of this group. The sixth group in which the lower ends of calcified tissue of the crown and the adjoining dental papillae were simultaneously removed showed the following picture : that is, according to varying degrees of damage given the teeth by the operation, the tooth roots showed different degrees of growth and this in turn directly affected on their prospect of eruption. Thus, eruption was possible in all 6 teeth where the mesial and distal roots had been normally developed. In the seventh group of teeth where major part of the dental papillae was excised, following picture was observed. Development of the enamel substance in the crown was only barely observed taking place at the residual part of dental papillae. There was never seen any sign of tissue regeneration of the dental papillae at the site of removal, and instead, there was filled by irregular osteoid-dentin proliferating from the inner wall of dentin and from the lower ends of hard tissue, and by osseous tissue proliferating from the base of dental crypt. All the teeth in this group remained

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In spite of great progress in enzymological, chemical and histo-chemical resarch of alkaline-phosphatase in recent years, there are many unsolved problems. A few reports of the histogenesis of alkaline-phosphatase have been published. Dr. Furuichi reported the distribution of alkaline-phosphatase in organs and tissues of chick embryo in 1942. The histogenesis of this enzym was not refered in his report. The principal objective for this study is consisted in difficulty of resarching the histogenesis of this enzym by histochemical method. A total of 100 ckick embryos dating from 2 to 20 days was used. The results obtained are showed in the following table. [table] In almost all the tissues and organs, the A. P. reaction was remarkably observed in the early embryonic stages, and then it became gradually feeble. Degree of A. P reaction is due mainly to verocity of growth. The alkaline phosphatase reaction is presumably produced in all progressive early embryonic tissues and organs.

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A histological study on the lyssa of a Sumatra tiger (male, estimating 10 old) led to the following summaries. 1) The tiger's lyssa is situated in the septum linguae, under the mucosa covering the lower surface of the tongue in the anterior part, under M. transversus linguae in the posterior part, its slender roundworm-like form being extended from the apex linguae to the vicinity of the fusing point of the frenulum linguae as well as other animal. It is about 5.5cm in length, 3.3mm in dorso-ventral thickness at the centoral part. 2) The matrix of the body was covered with a sheath of dense connective tissue, but its structure varied according to the longitudinal positions. a) The anterior part was composed mainly of chondroid tissue and basophile connective tissue being rich with cell (Fig. 1, 2) b) The central part was composed of basophile connective tissue and adipose tissue (Fig. 3, 4, 5) c) The posterior part resembles to the central part, but the matrix was divided into the basophilic connective tissue part and adipose tissue part by dense connective sheath. (Fig. 6, 7) At the posterior ending, however, its the former becames tapering away in the connective tissue of the septum linguae being lost basophile ability.

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Lingual papillae were studied on the zebra (Equus lebra) aged 12 old. The results were summarized as follows. On the dorsal surface of the tongue there were viewed, Papillae vallatae, Papillae foliatae, Papillae fungiformes, Papillae filiformes, and Papillae conus. 1) Papillae vallatae occurring counted 3. They were very large, longitudinal diameter 8∿10mm-, oval or longoval in shape. The taste buds numbering approximately 10-15 were located on the epithelium facing to the groove, but few in the rate of the size. 2) Papilae foliatae were small, longitudinal diameter 10mm, counted approximately 5-6 groove. The taste buds counted approximately 10-15. 3) Papillae fungiformes were distributed on the lateral margin of the anterior of the tongue (5-7 on each side). They lacked taste buds, but in the Lamina propria muoosa nerve fibers bundle were rich. 4) Papillae conus occured on the lateral margin of the tongue (30-40 on each side).

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The girl, seven yeors of age, showed marked retarded growth, delayed eruption of teeth, and absence of 2nd premolrs and 7th molars in both sides of lower jaw. Diagnosis by the Clinics of The Fuculty of Medicine, Kyushu University as due to a hypophyseal dwarfism, and previous history of the patient as disclosed by her parent that she was delivered in the midst of a flood, would seem to account well for the present condition of the girl. In this report, general observation including the physical state, blood pictures, mental state, as well as detailed appearance of the teeth were described, and treatment on the defective teeth including amputation and capping of the pulp was described.

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