1. The spontaneous mast cell tumor of the dog contains heparin. 2. The cytoplasmic particulate content of the tumor mast cells varies with their anaplasia. This conclusion is based on the following findings: (a) in the immature cell of the more malignant tumor the particulate matter appeared in the living cells by phase microscopy to be composed of greyish illdefined particles or as a fine, weakly metachromatic granulation in the fixed and stained preparation; (b) in the mature cells of a relatively benign mast cell tumor, both in the living cell and in stained preparations, the particulate matter occurred in the form of discrete, dense, and strongly metachromatic granules, resembling those of the normal mast cell. 3. The heparin content was large (fifty times that of dog liver) in the growth with mature cells and only moderate (1.7 times) in that with immature cells. 4. Since there may be a great amount of greyish particulate matter (or fine stained granules) in a tumor of relatively low heparin content, it is suggested that this material represents an early or precursor phase in the development of heparin. 5. This possibility and the fact that the blood stream may be invaded by mature tumor mast cells of large heparin content without evident disturbance in the coagulability of the blood suggest the value of a comprehensive biochemical study of the heparin of mast cell tumors.

Fragments from two mast cell tumors of the dog have been cultured in vitro. Studies on the living and on fixed and stained preparations revealed the following: Only mast cells grew out from the original tumor fragments though these contained other types of cells. They grew in some of the roller tube cultures in a sheet resembling an epithelium but in hanging drop cultures they lay separate and were irregularly spindle or star-shaped with long protoplasmic processes. The cytoplasmic granules of the proliferating mast cells varied in size, number, and tinctorial properties. In most of the cells they stained metachromatically, in occasional cells some of the granules only could be stained, and in a few none could be stained.

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A procedure is described for the separation and purification of 7-globulin from human placental extracts and postpartum blood. Frozen placentas together with the postpartum blood are thawed, chopped and extracted with isotonic saline. The initial separation of a fraction containing 7-globulin is accomplished by the addition of ethanol in the cold. A large part of the -globulins are separated from the 7-globulin fraction by the precipitation of the former at pH 4.8, and ethanol 8%. This is followed by the precipitation of a 7-globulin-rich (70%) fraction at pH 7.0-7.2 and ethanol 25%. A fraction rich (91%) in a-and /3-globulins is separated at pH 5.1 and ethanol 17%, leaving a supernatant fluid from which the 7-globulin is again precipitated with a final purity of 96%.

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