To chew, it is necessary to maintain harmony between the masseter muscle and other organs. Various studies have been conducted on the masseter muscle, but none has examined the relationships among masseter muscle form, occlusal support of remaining teeth, and maxillofacial morphology. Thus, we conducted the present study using cadavers donated to anatomy practice. After the masseter muscle was extracted, its length, width, thickness, and volume were measured; histological observations were conducted; and the muscle fiber cross-sectional area and muscle density were calculated. In addition, denture use and non-use were examined. The results showed that when regional support loss occurs, muscle fiber thickness and density decrease. This in turn causes masseter muscle thickness and volume to decrease, resulting in muscle atrophy. Furthermore, excluding Eichner class A cases (all regions intact), the thickness of the masseter muscle is greatest when the premolar support region remains. The premolar support region was shown to have the most impact on masseter muscle morphology. These results suggest that atrophy of the masseter muscle can be arrested or improved with the use of dentures in the case of tooth loss.

A male Holstein-Friesian calf with seven legs was examined macroscopically and radiographically. External features included two normal forelimbs, two normal hindlimbs (lateral hindlimbs), and two abnormal hindlimbs (medial hindlimbs) which were underdeveloped. Also, a rudimentary forelimb, which was attached to the pelvic region, was observed between both the medial hindlimbs. It consisted of an underdeveloped humerus, a duplicated ulna, several carpal bones, a partially duplicated metacarpal bone and three digits with three hoofs. This leg was connected with two sets of coxae by a irregular-shaped bone considered the vestigial vertebrae and ribs. Two penises and scrotums, three kidneys and testes were also observed. This calf is the first case of dipygus associated with pygopagus parasiticus in cattle. Based on these findings, the pathogenesis of this rare anomaly was briefly discussed from an embryological point of view.

in 2001, an anomaly of the kidneys was found. The lower ends of the kidneys were fused by a renal substance and formed a horseshoe kidney located ventral to the abdominal aorta and inferior vena cava. Both renal hila opened very widely in the ventral direction, with the left hilum being larger than the right. This horseshoe kidney had original left and right renal arteries that branched from the abdominal aorta. As well, there were four surplus renal arteries. The first surplus artery branched from the right renal artery and was distributed to the upper pole of the right kidney. The second arose from the abdominal aorta and was distributed to the inferior pole of the right kidney. The third arose from the abdominal aorta and was distributed to the inferior pole of the left kidney and part of the isthmus. The fourth branched from the abdominal aorta and was distributed to the upper pole of the left kidney. The incidence of horseshoe kidneys in Japanese anatomical dissections has been reported as 0.15-0.48%. This was the sixth such case for our laboratory, representing a frequency of 0.1% (6 of 1902 dissections) from 1952 to 2001.