チーター（Acinonyx jubatus）における半規管の配置と直交性について

The purpose of this study was to clarify the spatial orientation of the semicircular canals in the cheetah (Acinonyx jubatus) using computed tomography (CT). CT scan was performed on the skull of a cheetah. Scanning data were reconstructed into the cross-sectional images, and then the landmark coordinates were determined to define the planes of the semicircular canals and the cross-sections of the skull. In the cheetah, the lateral semicircular canal was parallel to the base of the skull. The angles between the anterior and posterior semicircular canals was lager than 90 degrees, and each canal showed the similar angle with the sagittal cross-section of the skull, although these planar directions were different. One limitation of this study is that here we provided only one specimen, and thus the present results need to be confirmed by examining a larger number of cases in future studies. However, the method outlined in this study provided quantitative descriptions of orientations and orthogonalities of the semicircular canals of the cheetah. This is potentially useful for indentifying the morphological features of the semicircular canals in felids

アメリカグマ（Ursus americanus），マレーグマ（Helarctos malayanus），ホッキョクグマ（Ursus maritimus）における手内筋の筋重量について

The hands of the American black bear (Ursus americanus), the sun bear (Helarctos malayanus), the polar bear (Ursus maritimus), and the lion (Panthera leo) were dissected and the mass of the intrinsic hand muscles were systematically recorded to explore possible interspecies variation. Muscle mass was divided by the third metacarpal bone size for normalization. The results indicated that the normalized muscle masses of the thenar muscles were larger in the three bears than the lion, and the abductor pollicis muscle was larger in the sun bear than other bears. For the abductor digiti minimi muscle, the normalized muscle mass was larger in the three bears than the lion, but smaller in the polar bear among three bears. One limitation of this study is that here we provided only one specimen for each species, and thus the present results need to be confirmed by examining a larger number of cases in future studies. However, these differences in the intrinsic hand muscles of the four species may reflect adaptation for their different habits