1. Laboratory of Veterinary Surgery, College of Bioresource Sciences, Nihon University, 1866 Kameino, Fujisawa-shi, Kanagawa 252, Japan
2. Japan Livestock Technology Association, 3-20-9 Yushima, Bunkyo-ku, Tokyo 113, Japan
3. Blood Horse Training Center, 1-1-10 Toranomon, Minato-ku, Tokyo 105, Japan