Stem cell in peripheral blood: a study by parabiosis of irradiated and non-irradiated animals. I. New approach to parabiosis as a method for hematologic study.

1. For the purpose to obtain parabiotic rats having well maintained humoral circulation, the author observed parabionts having coerio-anastomosis and vascular anastomosis. 2. In the parabiotic rats having coerio-auastomosis when one of the parabionts was prevented from taking food and water by mouth sealing, the animals died within 5 to 6 days just as the control animals subjected to complete starvation, indicating that in coerio-anastomosis no appreciable humoral exchange was established between the two parabionts. 3. In vascular parabiosis having cross anastomosis of the aortas with polyethylene tubules, the animals died about 24 hours after the operation because of blocking thrombosis formed in the polyethylene tubules. 4. In the vascular parabiosis having cross anastomosis of the aortas by the homologous thoracic aorta animals did not survive through the operation but those having parallel anastomosis of the aortas survived after the operation for 3 weeks at largest and they seem to serve as useful tool for the parabiosis experiment.