The eradication of cancerous growths from the body by other than surgical means will depend on the discovery of some vulnerability of the cancer cell which is not shared by the cells of the organism. Any property which differentiates the cancer cell from the normal cell must therefore be regarded as important, and I wish in this brief communication to direct attention to experiments which indicate that the cells of rat and mouse sarcomas are less resistant to heat than are normal connective-tissue cells of these animals when both are placed under similar experimental conditions. A number of observers have reported on the resistance of cancer cells to various chemical and physical agents. For example, it was shown that mouse carcinoma cells survive freezing with liquid air (Michaelis, Moore and Walker, Gaylord); or treatment with a 1: 3,500 solution of mercuric chlorid (Clowes); and that rat sarcoma cells (in emulsions)