14 MASS. EXPERIMENT STATION BULLETIN 370 



manifested itself as erythroblastic leukosis when used to inoculate chickens in 

 the usual manner. In 1935, Jarmai (100) reported the production of fibrosarcoma 

 with tissues (liver, spleen, and bone marrow) from birds affected with his strain 

 of erythroblastic leukosis. The sarcoma developed in the breast muscle of the 

 experimental chickens where the tissue for inoculation was implanted. The 

 tumors did not reach a large size and the experimental life of the birds was short 

 as in each instance erythroblastic leukosis was also present. He was able to trans- 

 mit the sarcoma through three serial passages after which he discontinued the 

 experiment. Stubbs (191) attempted to repeat this experiment of Jarmai using 

 Furth's Strain 1 agent, with the result that in 110 chickens receiving either 

 leukotic blood or organs intramuscularly, 61 instances of leukosis occurred with 

 no evidence of local tumor formation. 



Five different strains of experimental leukosis have been developed by the 

 Danish workers. Engelbreth-Holm and Rothe Meyer in 1935 (58) gave a general 

 review of their observations on the 5500 chickens inoculated with these five 

 strains. Erythroblastosis, myelosis, sarcoma, or a mixture of these conditions 

 developed in 3100 of these chickens. These strains have been somewhat variable 

 in respect to the types of disease produced. Strain R gave origin to 1255 cases of 

 erythroblastic leukosis, one case of granuloblastic leukosis, and nine cases of 

 mixed leukosis; Strain T divided itself into two branches, one of which produced 

 only erythroblastic leukosis whereas the other branch (TO brought about granu- 

 loblastic leukosis as well; Strain E-S produced both erythroblastic leukosis and 

 sarcoma; and Strains and AA gave rise only to pure erythroblastic leukosis. 

 The predominating form of disease in all strains was the erythroblastic type. 

 Engelbreth-Holm and Rothe Meyer (59) have emphasized that age of the ex- 

 perimental animal was a decisive factor in the question of susceptibility; birds 

 less than three months old were much more susceptible than those over six months 

 old. They have noted relatively few instances of granuloblastic leukosis in birds 

 over six months old. 



Rothe Meyer and Engelbreth-Holm first reported on Strain E-S in 1933 (171) 

 at which time their experiments concerned the use of 202 chickens. In this group 

 of inoculated birds 72 cases of erythroblastic leukosis developed, of which only 

 14 were typical and the remainder were of the anemic type. Fibrosarcoma de- 

 veloped in 60 chickens and 21 were affected with a combination of fibrosarcoma 

 and erythroblastic leukosis. In two instances granuloblastic leukosis developed 

 in association with fibrosarcoma. The transmissible tumor was composed of 

 spindle-cells and showed typical malignant invasion of the muscle structure 

 adjacent to the site of inoculation. Metastases to the visceral organs were very 

 infrequent. This strain of leukosis had its origin in a bird affected with granulo- 

 blastic leukosis and multiple sarcomatous tumors, and in the first few animal 

 passages there appeared to be two agents responsible for these dissimilar processes. 

 Intravenous inoculation of the blood of the original bird produced erythroblastic 

 leukosis in the first four animal passages, but in the fifth passage two cases of 

 sarcoma as well as two cases of erythroblastic leukosis were produced. Trans- 

 plantation of the original sarcoma produced sarcoma in five of ten experimental 

 birds so inoculated. Engelbreth-Holm and Rothe Meyer (58) have reported that 

 a leukosis-producing agent could not be completely separated from a sarcoma- 

 producing agent in Strain E-.S, although it was generally true that intravenous 

 inoculation resulted in the development of leukosis and intramuscular inoculation 

 was followed by local formation of sarcoma. The existence of only one agent in 

 this strain was indicated by the fact that erythroblastic leukosis was produced 

 without sarcoma for 43 animal passages and then, from the last animal passage. 



