1. Laboratory of Veterinary Anatomy, Department of Veterinary Medicine, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu 069-8501, Japan
2. Laboratory of Anatomy, Department of Basic Veterinary Science, Faculty of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
3. Laboratory of Agrobiomedical Science, Faculty of Agriculture, Hokkaido University, Sapporo 060-0818, Japan