1. The protein active SH radical in various blood diseases is generally reduced, but it is markedly so especially in leukemia and cancer. Of various leukemias the acute from shows a marked decreasing tendency. 2. As for mucoprotein on the other hand, a markedly high value is shown in leukemia, cancer and Hodgkin's disease, and even in this instance it is extremely high in the acute from of leukemia. On the contrary in other blood diseases the value is either nomal or at a slightly higher level. 3. Therefore, the protein index of Müller is positive in al most all leukemia, cancer and Hodgkin's disease, making it possible to distinguish them distinctly from other diseases. 4. No specal correlation can be found between the proiein active SH radical and mucoprotein on one hand and the liver function and serum protein fractions on the other. 5. Judging the fluctuations in the protein active SH radical and mucoprotein on the basis of results of treatment in blood diseases, there exists clearly a mutual relationship between the fluctuations and clinical symptoms. In other words, in luekemia the fluctuations in the protein active SH radical and mucoprotein are parallel with the fluctuations in the number of immature leucocytes, while in other blood diseascs the fluctuations parallel with the degree of anemia. 6. The protein active SH radical and mucoprotein in experimental anemia fluctuate in parallel with the degree of anemia and they take about the same course.