Summary: | Morphological observation was made on the pons of eighteen kinds of mammalian brains. On the ventral view of the pons, the appearance of it on lion, bear, indian elephant and blue whale was well developed respectively. The angle of the ventral projection of the pons in these animals, which was measured on the mid-sagittal plane, was larger than that of other animals and the area of the pons in this plane of the above mentioned animals also became larger for its volume. These observations corresponded to the gross inspections. Based on the observations on the human and mammalian pons, it is considered that the angle of the ventral projection of the pons indicates the degree of its development, that is, the pons had a large angle of the ventral projection, such pons naturally projects to ventral, is well developed. The morphometric difference among the order of animals could not be recognized. It is suspected that the degree of the development of the pons is correlated with the behavior and adaptation to the environment of mammals. departmental bulletin paper
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