Myeloid leucosis and erythroleucosis can be transmitted from one bird to others by emulsions of infiltrated organs, whole blood cells, and plasma. Inoculation is more often successful with blood cells or with whole blood than with plasma or with emulsions of organs infiltrated as the result of leucosis.

Inoculation with material from a bird with myeloid or with erythroleucosis produces both myeloid and erythroleucosis, and in many instances mixed forms with characters of both.

Evidence is wanting that lymphoid leucosis is caused by the agent that transmits myeloid and erythroleucosis. The occurrence of lymphoid leucosis among the birds inoculated with material from myeloid or erythroleucosis may be explained as spontaneous disease.

Injury to cellular structure by treatment with distilled water or by repeated freezing and thawing does not destroy the agent that transmits the disease.

Berkefeld filtrates have failed to transmit regularly myeloid or erythroleucosis. The evidence obtained shows, however, that the transmissible agent is filterable, although there are technical difficulties in its filtration.

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