Effect of drying with hot forced draft and of mincing bracken fern on its carcinogenic activity.

The carcinogenic activity of young bracken dried at a high temperature or minced by a mechanical chopper was compared with that of unprocessed bracken dried at room temperature. Inbred strain ACI rats of both sexes were divided into 4 groups; Group 1 received a diet containing the unprocessed bracken dried at a room temperature of below 30 degrees, Group 2 received a diet containing bracken dried at 70 approximately 90 degrees with a hot, forced draft, and Group 3 received the diet containing processed bracken that had been minced to a paste-like consistency using a mechanical chopper. The control group was fed a normal diet. Rats fed a bracken-containing diet developed tumors most frequently in the ileum. Comparison of Group 1 with Groups 2 and 3 showed no significant difference in the latent period, incidence, histologic types, or multiplicity of the intestinal tumors found in each animal.