1. Department of Anatomy II, School of Veterinary Medicine, Azabu University, 1–17–71 Fuchinobe, Chuoh-ku, Sagamihara 252–5201, Japan
2. Department of Veterinary Anatomy, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
3. Laboratory of Veterinary Pathology, School of Veterinary Medicine, Azabu University, 1–17–71 Fuchinobe, Chuoh-ku, Sagamihara 252–5201, Japan