A transmissible sarcoma of the chicken has been under observation in this laboratory for the past fourteen months, 1 and it has assumed of late a special interest because of its extreme malignancy and a tendency to wide-spread metastasis3 In a careful study of the growth, tests have been made to determine whether it can be transmitted by a filtrate free of the tumor cells. Attempts to so transmit rat, mouse, and dog tumors have never succeeded; and it was supposed that the sarcoma of the fowl would not differ from them in this regard, since it is a typical neoplasm. On the contrary, small quantities of a cell-free filtrate have sufficed to transmit the growth to susceptible fowls.

EXPERIMENTS.