On the number of red blood corpuscles contained in the defibrinated blood flowing out from glas tubes of different diameters, which correspond to arterioles of our body, the following observations are made. According to the experimental results, the number of red blood corpuscles increases with the increase of the diameter of tube. But when the stream in glas tube flows in whirls (i.e., Usd/η>2000 in Reynold's formula) the increase of red blood corpusrcles is not to be seen in spite of the increase of the diameter of tube.