1. Department of Theriogenology, Faculty of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Sagamihara-shi, Kanagawa 229, Japan
2. Department of Veterinary Radiology, Faculty of Veterinary Medicine, Azabu University, 1-17-71 Fuchinobe, Sagamihara-shi, Kanagawa 229, Japan
3. Department of Veterinary Surgery II, Azabu University, Faculty of Veterinary Medicine, 1-17-71 Fuchinobe, Sagamihara-shi, Kanagawa 229, Japan
4. Futtu Branch Office, Central Animal Clinical Center, Chiba Prefectural Federation of Agricultural Mutual Relief Associations, 267 Nakamasaishi, Sanuki, Futtu, Chiba 299-15, Japan