PERIOD OF INFECTIVITY OF PATIENTS WITH EXPERIMENTALLY INDUCED INFECTIOUS HEPATITIS.

1. Serum and stools obtained in the pre-icteric phase of one patient, and pooled specimens of the same materials from 5 patients with experimentally induced (by feeding) infectious hepatitis produced the disease in 10 out of 15 human volunteers following feeding or parenteral inoculation. 2. Pooled specimens of urine and nasopharyngeal washings from 5 patients, obtained in the acute phase of infectious hepatitis when virus was proven to be in the stool and serum, were not demonstrably infectious when fed and given intranasally to 6 volunteers. 3. Serum obtained in the midincubation period of one patient with experimentally induced infectious hepatitis failed to produce apparent infection when inoculated parenterally into 3 human volunteers. This is in contrast to the situation in homologous serum jaundice in which "virus" has been demonstrated in the sera of volunteers during the incubation period. 4. Serum and stools obtained from one patient and pooled specimens of stools from 5 patients 25 to 31 days after onset of experimental infectious hepatitis failed to produce apparent infection in 10 human volunteers. 5. No appreciable difference was detected in length of incubation period following the parenteral administration of widely different amounts of the same strain of "virus."