Fig. 2.

The generation of liver cancer in rats by oral administration of o-aminoazotoluene. The experiment was performed using 400 rats. Among them, 40 were control animals fed on rice without o-aminoazotoluene and 60 were used for determination of the amount of the reagent to be fed. The remaining 300 rats were divided into 3 experiments. Experiment 1: 63 rats were fed on rice containing o-aminoazotoluene and 3 rats each in a total of 21 groups were sacrificed every 15 days and anatomical tissue specimens were prepared. Experiment 2: 51 rats in 17 groups each containing 3 rats were fed on rice with o-aminoazotoluene, but every 15 days from 60 days after the start of the experiment a group of 3 rats were changed to be fed on rice without o-aminoazotoluene and continued to fed for the total number of days indicated. At the timepoint indicated, each rat was sacrificed and anatomically analyzed. Experiment 3: the remaining 186 rats were fed on rice containing o-aminoazotoluene from the start of the experiment. Open circle: tumor-negative rat. Closed circle: tumor-positive rat. (Modified from Table 1 of Ref. 13.)