The muscles of mastication of the polar bear (Ursus maritimus) and those of the brown bear (U. arctos) were examined by anatomical approach. In addition, the examination of the skull was carried out in the polar bear, brown bear and giant panda (Ailuropoda melanoleuca). In the polar bear, the rostro-ventral part of the superficial layer of the M. masseter possessed the abundant fleshy portion folded in the rostral and lateral directions like an accordion. Moreover, the rostro-medial area of the superficial layer became hollow in the nuchal direction when the mouth was closed. The M. temporalis of the polar bear covered up the anterior border of the coronoid process of the mandible and occupied the almost entire area of the cranial surface. The M. of the polar bear was inserted on the ventral border of the mandible and on the ventral part of the temporal bone more widely than that of the brown bear. As results of our measurements of the mandible, an effect of the leverage in the polar bear was the smallest in three species. In the polar bear, the skull was flat, and the space between zygomatic arch and ventral border of the mandible, occupied by the M. masseter was the narrowest. It is suggested that the muscles of mastication of the polar bear is adapted to the flat skull feature for supplementing the functions.

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An intramuscular lipoma is a deep-seated heterotopic benign mesenchymal tumor that originates in a skeletal muscle and infiltrates the adjacent muscle. It tends to recur after excision. This tumor is also referred to as “infiltrating lipoma" and differential diagnosis from well-differentiated liposarcoma is necessary.
Intramuscular lipoma is very rare in the oral and maxillofacial region. We describe a case of intramuscular lipoma occurring in the or lateralis that spread to the infratemporal fossa in association with mental nerve neuropathy in a 59-year-old man. With the patient under general anesthesia, we excised the tumor, including the circumferential tissue. At the 2.5-year postoperative evaluation, numbness had improved, with no evidence of recurrence.

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Latin anatomical names ofFossaeandFoveaein the skeleton were analyzed and compared with Japanese anatomical names for better understanding of the structures of the human body and for possible revision in the future.
The conclusions were as follows:
1. In general, round excavations were calledFoveae (singular: Fovea), and nonround excavations were calledFossae (singular: Fossa) . Some shallow excavations for articulation and some shallow excavations with the names which indicate their contents were calledFoveaeeven though they were not round.
2. Each name ofFossaecontained the word which indicates form, location or content ofFossa, the bone (or osseous structure) which articulates withFossa, or the muscle which is attached toFossa.
3. Each name ofFoveae contained the word which indicates location, content or articulation ofFovea, the bone (or osseous structure) which articulates withFovea, or the muscle (or muscular trochlea) which is attached toFovea.
4. The Japanese name which corresponds toFossa caninashould be changed from Kenshi (canine tooth) =ka (fossa) to Kenshikin (canine muscle) = ka or Koukakukyokin (levator anguli oris muscle) =ka.
5. The Japanese name which corresponds toFossa pterygopalatinashould be changed from Yoku (wing) = kougai (palate) = ka (fossa) to Yokutotsu (pterygoid process) = kougaikotsu (palatine bone) = ka.

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The facial artery and its ramifications in the rabbit were studied by the acryl plastic injection method. The facial artery arose independently from the external carotid artery or the maxillary inferomedial to the origin tendon of the digastricus muscle, or in common with the lingual artery. It curved inferomedially lateral to this muscle, but did not curve when its origin was located on the maxillary, where it gave rise to the styloglossal and the digastric branches, then the parotid branch medial to the ventral portion of the gland and the submandibular branch between this gland and the muscle. Both glandular branches in some cases supplied the submandibular lymph nodes and the skin. The artery then passed forwards on the medial surface of the and gave rise to the muscular branches for it and the maxillomandibular branch. The facial artery appeared on the face passing through the vascular notch of the mandible. The submental artery, giving off the infradigastric, the posterodigastric and the mylohyoid branches, curved forwards on the medial surface of the mandible and terminated at the insertion of the digastricus after giving rise to the supradigastric branches. Sometimes it supplied the lymph nodes and the skin covering an area beneath the symphysis and the submandibular region. The primary masseteric branch, giving off twigs to the maxillomandibularis muscle, passed through the vascular notch together with the facial artery and supplied the masseter muscle from its anteroinferior end. The facial passed along the anterior margin of this muscle and gave rise to the inferior labial depressor, the zygomaticoauricular branches and the inferior labial artery. It ascended between the zygomaticus and the buccinator, and finally divided into the superior labial artery and the oral angular branch in the middle of the buccinator, after giving off the secondary and the tertiary masseteric branches and the branch to the masseteric gland. The inferior labial artery passed anterosuperiorly between the buccinator and the zygomaticoauricularis, giving off the branches to the pars molaris of the buccinator and to the superficial mandibular gland and the inferior labial depressor branch up to the angle of the mouth, where it gave rise to the branch to the pars buccalis of the buccinator, the diastema and the gingival branches. It passed medially within the orbicularis oris and formed the inferior labial arterial arch by anastomosing with the opposite fellow. The secondary masseteric supplied the pars molaris and the the masseter from the medial side and the tertiary masseteric from the anterior margin. The branch to the masseteric gland supplied the pars molaris of the buccinator and divided into the anterior and posterior, which supplied the buccal mucosa and gingivae posterior to P₁.

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An investigation was made of the laminar structure of the masseter muscle in 3 lions (Panthera leo s. Fells leo), and the findings obtained were evaluated in comparison with those in some other carnivora. Although the general aspect of the masseter of the lion resembled that of the cat, there was no close similarity or analogy between them. The construction of the masseter in the lion was as follows. The superficial layer consisted of primary and secondary sublayers, the intermediate layer was composed of anterior and posterior portions, and the deep layer also had anterior and posterior portions. Among these three layers (the masseter proper muscle), the superficial layer was extremely well developed as a characteristic feature of this species. The maxillomandibularis muscle was developed in a muscular element of its origin and had its tendinous insertion on the anteroinferior margin of the masseteric fossa. The zygomaticomandibularis muscle was also fairly well developed in the form of two muscular bundles which originated from the temporal crest, a shelf forming a lateral protrusion on the basis of the zygomatic process, and its posterior surface. Both muscles were also well developed as the masseter improper. Such a huge and complicated laminar pattern of the masseter muscle in the lion should be sufficient to exert a strong force as a predatory animal.

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We examined the head of the gray wolf (Canis lupus) using MRI methods. Although the arising surface of the M. temporalis was not so enlarged in the frontal bone, the small frontal bone did not disturb the M. temporalis from occupying the lateral space of the frontal area in the gray wolf as in the domesticated dog. In the gray wolf, it is suggested that the M. temporalis may not be well-developed in terms of size of arising area, but in the thickness of running bundles. We suggest that the dog has changed the three-dimensional plan of the M. temporalis during the domestication and that the M. temporalis has developed a large arising surface in the frontal bone and lost the thickness of belly in the frontal area in accordance with the enlargement of the frontal bone and the increase in brain size.

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The facial artery and its ramifications in 7 adult common marmosets (Callithrix jacchus) were studied by the plastic injection method. The findings obtained are discussed in comparison with those for other primates. In the submandibular region, the facial artery arose from the external carotid artery at the height of the atlas via the linguofacial trunk on 10 of the total of 14 sides examined and independently on the other 4 sides. This common trunk always gave rise to the superior thyroid artery. The facial artery passed anterolaterally between the styloglossus muscle and the intermediate tendon of the digastricus muscle, giving off the styloglossal and the submandibular glandular branches, and anteroinferiorly medial to the muscle. In a position anterior to this muscle, the submental artery and masseteric branch were derived. The submental artery gave off the medial pterygoid, the digastric, the cutaneous, the sublingual glandular and the mylohyoid branches, and then continued up to the median line, where it terminated to supply the genioglossus muscle. In the facial region, the facial artery passed anterosuperiorly along the anterior margin of the masseter muscle on 12sides and away from it forwards on 2 sides, giving off the premasseteric branch in one of these 2 sides. It gave rise to the cutaneous, the buccal and the buccinator branches, the inferior labial artery and the communicating branch with the zygomatic artery. It terminated to divide into the superior labial and the naris lateral arteries, although the latter was lacking on 4 sides. The inferior labial artery gave off the mandibular marginal, the inferior labial marginal and the inferior labial glandular branches and terminated to anastomose with the mental artery. The superior labial artery divided into the superand deep branches, each of which continued as a nasal septal branch. The facial artery of the common marmoset usually ascended along the anterior margin of the masseter muscle and did not reach the medial angle of the eye.

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This study aimed to introduce a procedure for determining the bilinear elastic moduli (E1 and E2) of the periodontal ligament for a mathematical tooth model to analyse stress in the mandible. The bone and tooth morphology were scanned from a dry skull and an extracted intact tooth, respectively, and reconstructed in a three-dimensional finite element model. The model showed good agreement with previously reported in vivo premolar movement when an E1 for the first phase tooth movement of 0.05 MPa and an E2 for the second phase of 8.0 MPa with ε₁₂ of 0.075 were adopted. The mandible model analysis indicated that a remarkably high maximum compressive stress in the cervical cortical bone and the tensile stress in areas of masticatory muscle attachment were found. Future stress analyses using a jaw model may follow the process of determination of bilinear moduli to enhance accurate simulation with less calculation time.

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ハシブトガラスCorvus macrorhynchosとハシボソガラスC. coroneの最大咬合力と最大咬合圧について圧力測定フィルムを用いて測定し，体重や顎筋質量との関係を調べた．ハシブトガラスの顎筋質量，最大咬合力および最大咬合圧はハシボソガラスのそれに比べ有意に大きく，これらの値が体重に正の相関をすることが明らかになった．また，閉口筋質量1単位あたりの最大咬合力はハシブトガラスよりもハシボソガラスの方が大きいことがわかった．

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Variations in the patterns of origin of the inferior alveolar, the posterior deep temporal and the masseteric arteries when the maxillary artery passed medial to the lateralis muscle on 30 sides of 24 heads (10.8%) among a total of 278 sides of 139 heads of the Japanese, were investigated. The results obtained may be summarized as follows: 1. The maxillary artery gave off a common trunk between the inferior alveolar and the posterior deep temporal (76.7%), the latter distal to the former (16.7%) and in contact with their origins (6.7%). The masseteric artery always arose from the posterior deep temporal in 24 heads.2. The above-mentioned common trunk was observed in 52.1% of males and 47.9% of females, as well as on 56.5%of left sides and 43.5% of right sides.3. It can be said that the maxillary artery always passed medial to the lateralis, when the inferior alveolar arose in common with the posterior deep temporal.

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For the morphological classification of the muscles of mastication in man, and especially in order to understand the positional significance of the pterygolds in these muscles of mastication, the nerves of supply were examined minutely in five head-halves.
1. The nerves of supply of the masticatory muscles are classified into three categories depending upon the position of origin from the mandibular nerve.
(1) proximal nerves: the masseteric nerve, and the posterior and middle deep temporal nerves;
(2) intermediate nerves: the anterior deep temporal nerve, and the nerves to the lateral pterygoid, which are usually in a common trunk with the buccal nerve; and
(3) distal nerve: the nerve to the medial pterygoid.
While the nerve to the medial pterygoid arises from the medial surface of the mandibular nerve in close proximity to the otic ganglion, the other nerves tend to originate from the lateral surface. According to these differences, it would appear appropriate to classify the lateral pterygoid together with the masseter and temporalis as the lateral muscles of mastication, and only the medial pterygoid as the medial muscle of mastication.
2. The medial pterygoid is divided into anterior and posterior portions, but the laminate composition is not so distinct. The nerve of supply is divided into the medial, intermediate, lateral and posterior main branches.
3. The nerves of supply to the lateral pterygoid arise from the angle between the buccal and mandibular nerves and from the buccal nerve. Generally, the upper head nerves and lower head nerves originate separately. The more proximally a nerve arises, the more medially it tends to be distributed. Sometimes the lower head nerves wind upwards to enter the upper head as recurrent branches.

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Summary: The whole ramifications of the lingual artery and their distribution features in the rat were investigated by means of the acryl plastic injection method. For convenience, the tongue body was divided into fixed and unfixed (including the lingual apex) portions. The lingual artery arising from the external carotid artery gave rise to the ascending palatine artery and the hyoid branch, and its main stream terminated in the sublingual and the deep lingual arteries. The hyoid branch supplied the lingual radix asymmetrically. The sublingual artery was observed on the mylohyoideus muscle in all 200 examples, although it was always extremely underdeveloped. The deep lingual artery, ramificating into the styloglossal, the geniohyoid and the dorsal lingual branches in the fixed portion, passed forwards between the styloglossus and the genioglossus muscles and terminated in the dorsal branches in the fixed portion formed an arterial network, and one of them in this portion itself turned to the dorsal apical branch, which continued as the dorsal median branch. Vascular communications between the right and left sides within the tongue were interrupted by the presence of the lingual septum in the fixed portion of the lingual body, but in the unfixed portion were maintained by anastomoses between the dorsal and ventral median branches. In short, the deep lingual artery was observed mostly as a unilateral distribution feature in the fixed portion, but was bilateral in the unfixed portion.

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The potential of ocular toxicity of fenitrothion (O, O-dimethyl O-4-nitro-m-tolyl phosphorothioate) was assessed in Sprague-Dawley (Crj:CD) rats of both sexes receiving a diet containing the test compound at concentrations of 0, 2.5, 5, 10, or 30 ppm for 13 weeks. The animals were observed daily for clinical signs and their body weights and food consumption were measured weekly during the study. At termination of treatment, surviving animals were subjected to ophthalmoscopy, electroretinography, and biochemical analyses of plasma, erythrocyte, and brain cholinesterase (ChE). Histopathological examinations of ocular tissues were performed on all animals by light microscopy and on two animals/sex/dose by electron microscopy. There were no treatment-related changes in clinical signs, body weights, and food consumption. A significant inhibition of ChE activity was observed in males (plasma and erythrocyte ChE) and females (plasma, erythrocyte, and brain ChE) at 30 ppm and in females (plasma ChE) at 1O ppm. Ophthalmological and histopathological examinations revealed neither functional nor morphological alterations in the visual system at any dose level. Under the conditions of the present study, there was no evidence of ocular toxicity of fenitrothion for male and female rats at dose levels up to 30 ppm (1.70 mg/kg/day for males and 1.96 mg/kg/day for females) where distinct inhibition of ChE activity was observed.

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The mastication muscles were examined in the lesser (Tragulus javanicus) and greater mouse deer (Tragulus napu) to clarify the form of the mastication muscles in these primitive artiodactyls. The M. masseter was well-developed in both species, however the attachment area of its origin was not confirmed in the rostral facial part. The masseter bundles were not observed on the lateral side of the maxilla bone, and their origin was restricted to the zygomatic arch area. This suggests that the M. masseter may not act as a motor raising the mandible rostro-dorsally, but pull the insertion vertically unlike the highly derived grazer of Bovidae. The Crista temporalis was weak and the M. temporalis was thin in the mouse deer, and this indicates that the M. temporalis may not be important in the mastication in the primitive artiodactyls. These findings suggest that the browser such as mouse deer has been adapted for the feeding on soft leaves, and functional-morphologically different in mastication strategy from the grazer such as developed Bovidae species. The architecture of the mastication muscles was not different between the two species. However, in the muscle weight ratios per body weight, the M. temporalis and the M. digastricus were significantly smaller in greater mouse deer than in lesser mouse deer.

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