1. Laboratory of Animal Morphology, Faculty of Agriculture, Nagoya University, Nagoya, Aichi 464-8601, Japan
2. Laboratory of Animal Function and Morphology, Faculty of Agriculture, Utsunomiya University, Utsunomiya, Tochigi 321-8505, Japan
3. Present address: Anatomy of Physical Therapy Department, Toho University, Chiba 261-0023, Japan