The increased percentage of water in the liver of tumor-bearing animals, as reported by McEwen

METHODS Histological studies were performed on mito chondria in the livers of mice bearing malignant tumors. A total of 30 mice was used in the experi ment. The tumors were : transplanted fibrosar coma of the albino mouse, 9 animals ; Meyer tumor of the albino mouse (a mammary tumor of Brazil ian origin), 5 animals; spontaneous and trans planted mammary carcinoma of the CSH strain mouse, S animals. The livers of 5 albino and 5 CSH strain mice served as control. All animals had been kept on an ad libitum stock diet (1). The mice were killed while food was available in order to avoid alteration of the mitochondria by the lack of food. Animals bearing open necrotic tumors were discarded. Tumors of sacrificed animals were prepared and weighed separately. In order to cor relate the size of the liver with changes in mito chondria, the ratio liver/body was determined in each case, i.e., the gram value of the liver related to 1 gm. of body, deprived of its tumor. Pieces of liver were fixed in Regaud's fluid. Histological sections of S p were stained according to Altman's method. Ultraviolet light proved the best illumination for studying mitochondria mi croscopically, since acid-fuchsin-stained mitochon dna absorb ultraviolet light and are thus clearly defined. Sections of liver from tumor-bearing ani mals were compared with sections of liver from healthy animals.