Neurofibromas of Rat Ears Produced by Prolonged Feeding of Crude Ergot

As a result of an experiment to determine the chronic toxicity of crude ergot when fed to our inbred strain of Osborne-Mendel albino rats for 2 years, 23 of 38 rats on a 5 per cent dosage developed multiple tumors up to 8 mm. in diameter on their ears. Tumors appeared also on the ears of 9 of 38 rats on a 2 per cent dosage, but not on any of 38 on a i per cent dosage. 1 Histologically these tumors are neurofibromas, some showing distinct palisading of nuclei. They have appeared only on the ears. Male and female rats are affected alike. Among several hundred of our rats allowed to live normally or subjected to other experimental procedures, and whose ages equal those of the rats fed ergot, only one fairly similar tumor has appeared; this tumor was also on an ear. The tumors induced by the feeding of crude ergot are not truly malignant, inasmuch as they will regress markedly within a few weeks if feeding of the drug is stopped. Should the feeding be resumed they will then regain their former size and histologic appearance in 2 or 3 months. If the feeding is not resumed, some of the tumors will begin a spontaneous new growth after about 6 months.