After injecting various substances extracted from cancer tissues under the skin of mice and preparing serial slice specimms stained with hematoxilin and eosin, the author studied the exudation of leucocytes, and obtained the following results: 1. After fractionating proteins in various extracts of cancer tissues with (NH4)2SO4 and injecting each fraction under the skin of test mice, it has been found that the inflammationinducing factor is contained abundantly in the euglobulin fraction. 2. Even when the extracts of cancer tissues, devoid of proteins after the treatment with trichlor acetic acid or tannic acid, are injected similarly, a marked infiltration of leucocytes can be recognized. 3. When these extracts are injected in the similar way even after heating 30 minutes at 60 C, the exudation of leucocytes can be observed markedly. 4. Substance extracted from cancer tissues by the same treatment as employed in extracting Menkin's leukotaxin demonstrates to contain a factor that induces a marked exudation of leucocytes.