Researching into the condition of dispersion of blood-platelets in blood-vessels, the following results were obtained. 1) In the case of a normal rabbit, an injection of adrenalin caused a remarkable increase of blood-platelets as well as of white blood corpuscles, but after. splenectomy, this increase did not occur. 2) When atropin was injected, the number of blood-platelets decreased proportion-ately with the decrease of the white blood corpuscles. 3) An increase of blood-platelets was also demonstrable after administration of milk, presenting a condition which bore a resemblance to leucocytosis by digestion. But after splenectomy, administration of milk did not induce the increase of white blood corpuscles. In this case the number of blood-platelets also tended to decrease. 4) After the operation of cutting the vagus nerves at the cervix, white blood corpus-cles as well as blood-platelets decreased in the peripheral blood-vessels, and in the spleen, the blood-platelets of the veins showed a greater increase than those of the arteries; this indicated that there was some difference from normal conditions. In this case, no increase of white blood corpuscles and of blood-platelets by digestion was observed in the peripheral vessels. The quantitative relation of these blood corpuscles in the splenic vessels remains constant (Namely, there are more blood corpuscles in the veins than in the arteries, ) not only in the normal condition but also after cutting vagus nerves. 5) After cutting the cervical cord, a remarkable decrease of white blood corpuscles and of blood-platelets in the peripheral vessels was observed, and the splenic arteries and veins showed some difference from their normal condition, namely, there were more blood-platelets and red blood corpuscles in the splenic veins than in the splenic arteries. In this case the changes by digestion, which were so remarkable in normal conditions, did not occur in any blood vessels. In fine, it was concluded that the blood-platelets and white blood corpuscles undergo a common numerical change, and that the division of the former platelet is modified by the abnormal function of the autonomic nervous system.