(1) Comparing with the general observations on white bloodcells in blood-stream of the healthy swine, leucopenia was demonstrated to be characteristic of the blood of the animal affected with hog-cholera and numerical changes of leucocytes as well as lymphocytes during the course of the disease are as follows:
(a) A sudden decrease of leucocytes was demonstrated after the inoculation of the virus and their gradual reduction caused the minimum count at the stage of crisis. Based on numerical changes of each variety of leucocytes, the leucopenia seemed, to due to the diminution of neutrophiles originating from granulocytes in the bone-marrow.
(b) The numerical change of lymphocytes was generally observed resulting in the increase of the relative number in accordance with the development of the disease, contrary to the decrease of neutrophiles. But the absolute number of lymphocytes scarcely changed as compared with the number of neutrophiles.
(c) The count of eosinophiles showed a gradual reduction in accordance with the appearance of symptoms, and they were almost absent in blood-stream when the diseased animal became feverish. The relative number of stimulating-forms, monocytes as well as transitional-forms decreased at the feverish stage, but increased at recovery.
(d) A sudden reduction of blood-platelets was found after the injection of the virus and then their gradual decrease occurred in parallel with the development of the disease, but no noticeable change in the ratio of each type was observed.
(2) The swine injected with an attenuated virus showed the different numerical changes of white blood-cells as well as bloodplatelets depending on the degree of attenuation of the virus: when an strongly attenuated virus was used, slight leucocytosis and a gradual increase of blood-platelets were generally found; on the contrary, when an weakly attenuated virus was employed, leucopenia, lymphocytosis and a gradual reduction of blood-platelets were demonstrated as in the animal affected with hog-cholera.
(3) Judging from the haernacytological changes above-mentioned in circulating blood of the swine examined in different conditions, the diminution of leucocytes as well as blood-platelets and the relative increase of lymphocytes may be reasonably considered to be worthy in making early-diagnosis in some cases suspicious of hog-cholera at least.

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