1. Department of Anatomy, Yokohama City University School of Medicine, Fukuura, Kanazawaku, Yokohama 236, Japan
2. Department of Biology, Kawasaki Medical School, Kurashiki 701-01, Japan
3. Department of Anatomy, Yamaguchi University School of Medicine, Ube, Yamaguchi 755, Japan
4. Department of Dermatology, Yokohama City University School of Medicine, Yokohama 236, Japan