The employment of small animals suffering from cancer for purposes of laboratory experimentation has brought to light the fact that the endemic occurrence of cancer in animals is a not uncommon phenomenon. The classical case of carcinoma in rats reported by Hanau1 and the more recent observation of endemic occurrence of carcinoma of the breast in mice by Borrel2 are well known. Michaelis3 has likewise recently reported the finding in the course of one year in a single cage of 5 cases of carcinoma in the mouse. Loeb4 refers to an article by Cooper, in the Veterinarian, on the endemic occurrence of cancer of the parotid and submaxillary glands in the cow, and has himself reported the endemic occurrence of epithelioma of the inner angle of the eye in cattle observed in the Chicago stockyards.
The endemic occurrence of malignant tumors in animals, especially laboratory animals