The morphological changes observed in dog kidney cultured cells infected with distemper virus (Hokkaido strain) were compared cytochemically with those of measlea virus (Edmonston strain). The results were as follows.
1) Twelve to fourteen after inoculation the CPE was first observed in dog kidney cells infected with distemper virus. The appearanoe of the CPE was seven to ten days later than that of measles virus.
2) The CPE of the distemper virus infected cells was the same multinucleated giant cells, cytoplasmic inclusion bodies, and intranuclear inolusion bodies as those observed in the measles virus infected cell.
3) Both the inclusion bodies in the distemper virus infected cells also showed Feuglen negative, red staining with methylgreen pyronine, RNase resistent, and the cytoplasmic inclusion bodies blue to bluish green, otherwise the intranuclear inclusion bodies unstainable with acridine orange. This indicates that as with measles virus infection the cytoplasmic inclusion bodies have RNA, acid mucopolysacchrides and basic proteins, the intranuclear inclusion bodies no nucleic acids.
4) In the tissue culture cells inoculated with distemper virus the intranuclear inclusion bodies appeared at the same time or a few days earlier than the cytoplasmic inclusion bodies when stained with Giemsa or acridine orange.
5) The red particles in the cytoplasma of the measles virus infected cells were not detected in the cells inoculated with distemper virus when stained with acridine orange.
6) With acridine orange staining there were no differences of largeness and brightness of the nuclei and nucleoli between the distemper virus infected cells and the control cells. Then it seemed seldom to be an increased metabolism of nucleic acids.
7) Summing up, the morphorogical changes in the tissue culture cells infected with measles virus and distemper virus were quite the same except for the appearance of the CPE after virus inoculation.