A study of three new duck variants of the Rous chicken sarcoma.

Past studies have disclosed the fact that the virus of the Rous sarcoma of chickens can be adapted to alien species of birds provided, first, that young or newborn individuals be injected with the tumor material (2, 3) and second, that this tumor had been grown in chickens of a certain age (4). By fulfilling these requirements, several other duck strains of chicken tumors have been obtained. Three of them, variants of the Rous sarcoma, will be here described because they show interesting features differing from those of the sarcoma strains previously obtained from the same Rous tumor. The method followed consisted of injection into the breasts of newborn ducklings of 3 cc. of a cell suspension of the chicken tumor at 1:5 in saline, and of analogous passages into other ducks of the tmnors induced in the foregoing passage, using in these passages the same or a much smaller inoculum. Filtrates were also used. The original chicken tumor, as well as duck tumors from different passages were also tested on chicks and chickens by injecting from 0.5 to 3 cc. of cell suspensions in the breast, or 1 cc. or more of filtrate in either the breast or the vein. Adaptation of the virus to ducks was first recognized by gross and microscopic changes in the primary tumors, by the appearance of genera]ized leslons, and by the ability to infect older ducks with tumor materlal. The strains are designated 14(e), 14(d) l l , and 14(d)7. Stra~z 14(e) . -The donor host was a chicken 3 months old injected 13 days before with a cell suspendon of the Rous sarcoma. This is the youngest chicken in which a tumor grew which proved to be most easily adaptable to ducks. Filtrates and cell suspensions of this tumor were %und to be very active for chicks and ch i ckens.