The probability of a colony which originated as a single stem cell to become extinct due to differentiation of all of its stem cells in any generation is closely connected to stem cell self renewal probability p . p can be determined from the coefficient of variation of the colony numbers received by reinjecting single colonies of the same age. Whole spleens containing a known average colony number can also be used with advantage for this purpose. The results of both procedures indicate a stem cell self renewal probability p = 0.62 ? 0.04, which does not change significantly between the sixth and the fourteenth day of colony development, and an extinction probability

A technique for electrophoretic analysis of the hemoglobin mixtures from single erythrocytes has been developed. Hemoglobin mixtures were separated into their constituents, A(2), A, C, S, and J, at least qualitatively.

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In order to measure the total number of stem cells present in a given preparation, it is necessary to know the fraction of stem cells which settle in the spleen and form macroscopically visible colonies. The intravenous injection does not allow a direct measurement of this fraction. However, its value is established by injecting stem cells directly into the spleen, thus minimizing the dilution of stem cells through the circulation. It has been measured with this procedure, that only 4% of intravenously injected stem cells form spleen colonies.

No abstract