The incidence of cancer in various strains of mice.

Abstract

A number of investigators noticed the repeated occurrence of a particular kind of cancer in animals living either in the same cages or on the same farm. One of us described such observations in the case of carcinoma of the inner canthus of the eye in cattle found in increased number on a farm in Wyoming and in the case of three sarcomata of the thyroid in a relatively small number of white rats kept in a few cages in the laboratory of the Chicago Polyclinic and compared this phenomenon to the so-called endemic occurrence in man, but emphasized from the beginning that we had to consider not only infectious, but also hereditary conditions as possible causative factors. While in the case of certain cancers, for instance the squamous cell carcinoma of rats observed by Hanau, the above mentioned carcinoma in cattle and the sarcoma of thyroids of rats and some other similar cases observed by Borrel and others the unusual frequency of the reported cases in certain places could not be doubted, the significance of similar observations concerning the frequent occurrence of mammary cancer in mice were less clear, inasmuch as mammary cancer of mice is found everywhere and sufficient comparative statistics do not exist as yet as to the normal incidence of cancer in various strains of mice. Our investigations were therefore concerned with the incidence of cancer among various strains of mice kept in the same breeding establishment, especially with the view to decide definitely whether or not a hereditary factor was detectible in the occurrence of spontaneous cancers in mice. The principal results of our investigations which, after a few preliminary observations were begun more than three years ago, and which we hope to be able to continue, may be summarized as follows: