1. Laboratory of Veterinary Anatomy, Faculty of Agriculture, Iwate University, Morioka, Iwate 020–8550, Japan
2. United Graduate School of Veterinary Sciences, Gifu University, Gifu 501–1193, Japan
3. Laboratory of Veterinary Anatomy, School of Veterinary Medicine, Kitasato University, Towada, Aomori 034–8628, Japan