Investigations as to the nature of German measles are totally lacking. This is probably due to the fact that this disease is mild and so rarely encountered in hospital wards. The only opportunity afforded for a systematic study from a laboratory standpoint is the occurrence of an epidemic in an institution where children are housed in large numbers. An occasion of this kind—an epidemic attacking fifty or more children in an infant asylum—led to the present investigation, which includes a bacteriological study of the blood, inoculations of blood into monkeys with the object of producing the disease, and a cellular examination of the blood during the period of incubation of the disease.
In four instances the blood was obtained for bacteriological examination. In three of the cases the rash had been present for less than twenty-four hours, and in the fourth for about thirty-six hours; in two the