The induction of neoplasms of the urinary bladder of the cow and the small intestine of the rat by feeding bracken fern (Pteris aquilina).

Cattle were fed a diet containing bracken fern in the continuation of a study of the urinary bladder neoplasms produced under these conditions. One of the cattle died of a traumatic pericarditis and had no bladder lesion at 485 days. The other six animals fed bracken fern for from 510 to 1920 days all had gross bladder neoplasms. Four of the six animals with gross bladder neoplasms had transitional-cell carcinomas as well as hemangiomas. The remaining two animals had gross papillomas and hemangiomas, up to 3 cm in diameter. The cattle with bladder tumors all had gross hematuria for months or years before death. Although no control animals were autopsied during the past 2 years, the controls at that time were without tumors. During the 7 years of the study no control animal has had even microhematuria. Thirteen of ninety rats fed bracken fern mixed with a grain diet have died after 8 months and each animal had multiple adenocarcinomas of the small intestine. Six of these thirteen animals also had gross tumors in the urinary bladder. Since the study is in progress, no further information about these bladder lesions is available at this time.