방사선(放射線)을 조사(照射)할 때의 생쥐의 연령(年齡)과 방사선(放射線) 조사후(照射後) 시문경과(時問經過)에 따른 염색체이상(染色體異常) 빈도(頻度)와의 상호관계를 밝히기 위하여 40, 150, 300일(日)된 생쥐에 200 rad의 ${gamma}$선(線)을 전신일시(全身一時) 조사(照射)하여 1, 2, 4, 8, 16, 30, 60, 90일(日) 이 경과(經過)한 8개(個)의 실험군(實驗群)을 대상으로 골수세포(骨髓細胞)의 염색체(染色體)를 관찰하여 다음과 같은 결과(結果)를 얻었다. 8개(個)의 실험군(實驗群)에 있어서 염색체이상(染色體異常)을 가진 세포(細胞)의 빈도(頻度)는 40일(日)된 생쥐에서는 53.0%, 21.5%, 8.4%, 8.4%, 12.0%, 8.0%, 7.0%, 5.0%였고 150일(日)된 생쥐에서는 32.5%, 12.1%, 10.5%, 12.8%, 0.03%, 9.7%, 7.0%, 4.2%였으며 그러고 300일(日)된 생쥐인 경우는 27.7%, 13.6%, 9.0%, 9.3%, 13.3%, 14.4%, 7.5%, 9.5%였다. 방사선(放射線) 조사후(照射後) 2일(日) 이내에서는 늙은 쥐보다 어린 쥐에서 염색체이상(染色體異常)의 빈도(頻度)가 높았고 방사선(放射線) 조사후(照射後) 4일(日) 이후에는 반대로 어린쥐보다 늙은 쥐에서 염색체이상(染色體異常)의 빈도(頻度)가 높은 경향이 있었다.
To study the relationships among the frequency of chromosomal aberration induced by radiation, mouse age at the time of exposure and elapsed time after the irradiation, the 40, 150 and 300 day old mice were irradiated by gamma rays to 200 rad of acute whole body doses. The bone marrow chromosomes were observed in 8 experimental groups such as 1, 2, 3, 4, 8, 16, 30, 60 and 90 days after irradiation. In the 40 day old mice the frequencies of cell with chromosomal aberration were 53.0%, 21.5%, 8.4%, 8.4%, 12.0%, 8.0%, 7.0% and 5.0% in 8 experimental groups, in the 150 day old mice 32.5%, 12.1%, 10.5%, 12.8%, 0.03%, 9.7%, 7.0% and 4.2%. The 300 day old mice showed that the frequencies of cells with chromosomal aberration were 27.7%, 13.6%, 9.0%, 9.3%, 13.3%, 14.4%, 7.5% and 9.5% in each experimental group. There were tendencies that the frequencies of cell with chromosomal aberration were higher in the young mice than the old ones within 2 days after the irradiation but in the old mice than the young ones after 4 days.
