From the investigation into the influence of the spleen and the thyroid gland upon sedimentation, the following results were obtained. 1. Thyroidectomy seems to bring about the tendency of retardation of the blood sedimentation. On the other hand, this reaction is prompted by the administration of thyreoidin. On these occasions no definite changes was seen in the quantitative proportion of globulin to albumin. 2. This reaction is prompted by splenectomy, and at the same time the degree of viscosity increases, that of globulin remarkably, and when silverelecroid is injected continually, the same reactions occur, though less strongly. 3. Judging from the above-stated experimental fact we are led to believe that the thyroid gland has a function of prompting the sedimentation of the red blood corpuscles, which the spleen restricts when they are operative in the function of blood-making, in the same way as these two organs have two diflerent infiuences on the bone-marrow.