Chromosomes of “Mongoloid” Hamsters.∗

Summary The chromosomes were studied in 8 adult Syrian hamsters which had developed “mongolism” following an intracerebral inoculation of virus in the neonatal period. No significant chromosome abnormalities were detected. It is concluded that viral-induced “mongolism” in the hamster is an example of selective postnatal developmental arrest and that the particular manifestations of the condition can be accounted for on the basis of cell depletion due to the lethal effect of virus on dividing cells.