Further observations on the survival time of mice bearing chemically induced fibrosarcomas.

(wheren is numberof mice),wasusedto test levels of significance. One hundred and thirty-one female mice belonging to litters 4—11within the same latent period class (latent period < 100 days) lived, on an average, [email protected] days. This is a median value of 99.0 ± @.4days. There is a difference of 33.0 ±3.4 days between the two groups. This is 9.6 X P.E. Thus, there is a significant increase of survival time with female mice belonging to litters 4—11, as compared to female mice belonging to litters 1—3. In the two groups of female mice developing fibrosarcomas with latent periods between 101 and @00days, the following values on survival times were obtained : 156 female mice belonging to litters 1—3showed an average survival time value of [email protected] Recent data have shown that the survival time of mice of the Prunt inbred strain bearing chemi cally induced fibrosarcomas is influenced by litter seriation (@, 3). It was determined that female mice developing fibrosarcomas with latent periods of less than 100 days lived longer when they be longed to late rather than early litters of the same breeding mice (188 mice) (s). This shift in survival time was not observed in female mice which devel oped tumors with latent periods between 101 and @00days (148 mice) (3).