Abstract
AKIBA reported that Plasmodium isolated from fowls in Japan was identical withPlasmodium juxtanucleare recovered by VERSIANI and GOMES in Brazil, except that theformer was less virulent; i.e., the Brazilian strain (l4A) and tlte Mexican strain (l4B) arehighly virulent for chickens or adult chicks, while the Japanese strains are not so virulent.The authors observed that the strain of Plasmodium isolated from a chicken by theauthors was highly virulent for chickens, and that its exoerythrocytic forms were easilydetectable in various organs. Experiments were carried out on exoerythrocytic forms col-lected from organs of infected claickens one or two days old which had been inoculatedwith 0.2 to 0.5 ml of parasitized blood by the intracardial, intraperitoneal, and subcutane-ously route. The results obtained are as follows:l. Morphological observation.The size of schizonts and tlae number of merozoites of endoerythrocytic forms andexoerythrocytic forms are shown in Table 1. The endoerythrocytic form of this straincould not be distinguished fronn P. juxtanucleare morphologically. It was large in size andround, elliptc, or very long in form when it was in the brain and spinal cord. In the adrenal gland, ovary, and tlnymus, it was frequently obserxed that tent or more roundforms surrounded a ltost cell. The majority of tl?e cytoplasrn was stained faint blue andthe remaining portion deep blue or faint pink with Giemsa stain. There were poly-morphours nucleoides (merozoite) reddish violet in color.Exoerythrocytic-like forms were observed in 6 of the 108 chickents used in tltis experiment. They were present wltolly within blood cells. Tlaey were found in about 5 percent mature red cells, 55 per cent polychromerythrocytes, 18 per cent erythroblasts, and 22per cent juvenile leukocytes. Ill almost all the ltost cells, tlae ttucleus was oppressed bythese parasites. There was not difference in morphological claaracteristics between theseparasites and the exoerytlarocytic form.2. The period of appearartce of exoerytltrocytic forms.The Iengtla of the period of appearance was determined by examining 6 chickenswhich had been killed daily or laad died after inoculation. Tlte parasite appeared in thespleen first, that is, on tlae 5th day after inoculation, in tlue lung and kidney on tone 6tladay, in the liver and ovary on the 7th day, in the adrenal gland on tlne 8th day, in thebone marrow, myocard, and thymus on the 1 lth day, in the pancreas, spinal cord, medullaoblongata, and testicle out the 14th day, in the brain on tlae 16th day, and in the gizzardon the 17th day after inoculation.3. Organotropism of exoerythrocytic forms.The thymus was an organ in which exoerythrocytic forms ltad been found most Ire-quently. It was followed by the adrenal gland, spleen, liver, lunag, and bone marrow infrequence.4. Relationship of propagation between erndoerythrocytic and exoerytltrocytic forms.Endoerythrocytic forms showed the highest propagatiorn on tlte 10th da)r and a sud-den decrease in number in the 2nd week after inoculation. Thereafter, they showedirregular fluctuations in number for a long time. Exoerythrocytic forms began to in increase2 weeks after inoculation. While there was a decline in endoerytltrocytic f
