The quantitative results of different criteria of effect in 5 repeated-dose studies, using rats or dogs, are presented. In these cases, in percentage of lymphocytes, serum urea nitrogen, mortality, body weight, and tumor incidence, it is apparent that statistically significant differences between the chemical-treated and control groups were the result of abnormal values in the concurrently dosed controls. Therefore, it is concluded that, to be indicative of deleterious effect, changes must be produced that are dosage-related and illustrate a trend away from the norm for that stock of animals. © 1969.
