Skeletal variations in the various strains of mice (C57BL/6HeMs, CF#1, RF, and C3H/AnHeMs) and their F1 hybrids which were produced by reciprocal crosses of three inbred strains (C57BL/6, CF#1, and RF) were demonstrated. These strains were bred and maintained by the sister-brother matings since 1960 in the Natonal Institute of Radiological Sciemces. Examined bones are followings: interfrontal bone, cervical vertebrae, thoracic vertebrae and ribs, lumber vertebrae, sacral vertebrae, and caudal vertebrae. The same analysis was carried out further with the ICR-JCL mice which were bred and supplied in the Central Laboratories for Experimental animals. The data obtained were presented in Table 1-6.
Frequency of “interfrontal bone” was higher in C57BL/6 and RF strains (about 27%), and lower in others. The cervical vertebrae were 7 in all strains and their F1 hybrids. The fusion between cervical vertebrae (other than atlas-axis fusions) was seen frequently in the C57BL/6 (31% in all specimens of the C57BL/6), but none was found in ohers. Variations in thoracic vertebrae and ribs were found in CF#1 (17%), RF (7.1%), and ICR (6.1%) . These variations included the 13¹⁴, 14¹³, and 14 thoracic vertebrae (i. e. rib-bearing) . Other strains of mice kept always 13 thoracic vertebrae without variations.
The lumber vertebral numbers of C3H, ICR, and RF were predominantly 6. On the other had, the mice with 5 lumber vertebrae were appeared in the C57BL/6 (20.5%), CF#1 (13.8%), (C57BL/6 × CF#1) F1 (15.3%), and (C57BL/6 × RF) F1 (11.1%) with compared to the other strains and their F1 hybrids.
Two types were obseved with the pattern of sacral vertebrae : 4 bone-fused type and 3 bone-fused one. The former was found in the CF#1 (100.0%), C3H (96.5/), RF (94.4%), and ICR (67.7%), the latter was found frequently in C57BL/6 (58.9%), and the F1 mice from C57BL/6 males and females. Caudal vertebral numbers of the adult mice were distributed between 27 and 35. The largest numbers were found in the ICR and the smallest were observed in the C3H and C57BL/6 strains of mice.

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1959年から, 処女マウスでありながら乳腺〓胞形成を示す点で特徴的なマウス系統の育種をはじめた。選抜方法は, ♀では直接に乳腺を検索し, 乳腺〓胞を示した個体もしくはその姉妹を交配に用い, ♂は後代検定もしくは兄弟検定によった。♀は離乳日からすべてその全姉妹と同一ケージに収容し, ♂の臭いにさらした。乳腺の検索は10～14週令に行った。
1961年の後半に1対のマウスをえらび, それらの後代について自発性乳腺〓胞形成の頻度をしらべたところ, 直系群では74.3%, 傍系群では54.8%を示した。それら2群の後代でさらに選抜をつづけたところ, 11週令時乳腺検索において49.7%を示した。これらマウスは13週令時検索には, 100%に近い頻度を示すと思われる。
系統育成につづく今後の維持の問題として交配法をとりあげて考察し, さらに本系統の繁殖性における効用について述べた。

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脱毛性半致死マウスをCFW集団中に発見しその脱毛の発生過程と症状を明かにし, ついでvirus, 細菌, 外部寄生虫の検索, 感染実験, ならびに遺伝因子分析のための交配実験を行った。
結果はつぎのように要約される。
1) 異常は乳のみ期にはじまり異常分泌によると思われるフケの蓄積とそれにひき続きおこる脱毛, 再生のくり返しで, この症状はいずれの場合も典型的に発現する。
2) こういった乳のみ異常マウス (CFW/ab) の脳をサル腎細胞およびL細胞に接種したがReovirusの存在は証明されなかった。また, 皮膚分泌物からサブロー培地に分離した酵母を2週令正常マウスの皮膚に塗抹ならびに腹腔内に接種したが同様の異常をおこすことはできずまた同居によって正常マウスに感染させえなかった。
また被毛加温法により外部寄生虫は見出されなかった。
3) CFW/abと正常マウスとの交配によるF2においては, 正常: 異常が3: 1に分離することにより, 異常の原因は単純劣性因子でかつ伴性遺伝因子ではないと考えられる。
4) albino, black, agoutiを決定する各毛色因子とab因子とが独立であるという推定は否定される。
5) ab因子は半致死として発現する。

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It is very important for the prevention of Polyoma virus infection to study on the effect of aseptic agents on this virus, and this is clear from our article “On the Handling of Polyoma Virus” which has been published before in this Journal (Bull. Exp. Anim., 11 (3) 130. 1962) . To clarify this problem we have examined the effect of several kinds of drugs, which are generally used, on the Polyoma virus in vitro. Six aseptic agents, namely cresol, sodium hypochlorite, phenol, benzalkonium chloride, benzethonium, chloride, and alkyl polyaminoethyl glycine chloride have been studied and it is clarified that the cationic soap especially benzalkonium chloride is most effective and cresol or alkyl polyaminoethyl glycine chloride is slightly effective. By using 1/500 of lOw/v% benzalkonium chloride in vitro at room temperature for 30 minutes the infectivity and hemagglutination of Polyoma virus (TCID₅₀: 10_3.25) are completely inhibited.

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