12 MASS. EXPERIMENT STATION BULLETIN 370 



agent soon lost its potency in the chicken egg at incubator temperature. An 

 experiment was reported by Jarmai (98) in which he injected the agent of leukosis 

 into eggs on the first, fifth, eighth, twelfth, and thirteenth days of incubation. 

 Only healthy chicks were hatched from the eggs which received injections up to 

 and including the eighth day of incubation, whereas chicks with leukosis were 

 hatched from the eggs infected with the agent after the tenth day of incubation. 

 As pointed out by Jarmai, the myeloid tissue of the bone marrow is developed 

 on the tenth day of embryonic life (Dantschakoff 29). Jarmai considered this 

 as evidence that the agent of transmissible leukosis was not capable of develop- 

 ment independent from bone marrow tissue. It is of interest that Furth and Breedis 

 (84) founo that their Strain 1 fowl leukosis agent (pure erythroblastic and granu- 

 loblastic leukosis) would survive for at least thirty days in a tissue culture which 

 contained mononuclear cells presumed to be myeloblasts, whereas the agent 

 perished in a culture composed of sarcoma cells only. 



Van den Berghe and d'Ursel (206 b) have hatched chicks from eggs in which 

 the leukosis agent was being carried in serial passage on the chorio-allantoic 

 membrane. A total of six chicks was hatched from eggs that received blood 

 of embryos or embryo emulsion containing the leukosis agent after from one to 

 four serial passages on chorio-allantoic membranes. Five of these chicks had 

 changes of the blood characteristic of leukosis and died from 8 to 19 days after 

 hatching. The sixth chick lived only four days. Blood from two of the leukotic 

 chicks produced typical leukosis in chickens into which it was injected. The 

 five leukotic chicks had a paralysis of the legs, which developed on either the 

 first, second, or third day after hatching. These workers suggest this as evidence 

 of the ability of the leukosis agent to cause fowl paralysis. They do not describe 

 the gross or microscopic anatomy of the nerve tissue and, therefore, this sugges- 

 tion must await further evidence. 



Experimental Transmission 



Leukosis has been transmitted from a bird ill with the disease to a susceptible 

 bird by the use of whole blood, blood plasma, ascitic fluid, or emulsions of the 

 organs of the diseased bird (Eliermann and Bang 45, Ellermann 42, Schmeisser 

 177, Bayon 7, Furth 69, 70, and 71, Jarmai 97, Engelbreth-Holm 47, Olson 155, 

 Oberling and Guerin 146, and Nyfeldt 142). These materials containing the 

 inciting agent have been introduced into the recipient by either intravenous, 

 subcutaneous, intramuscular, or intraperitoneal inoculation and have produced 

 the disease. Wakamatsu (209) found the infective agent to be present in brain 

 tissue but not in the bile of affected chickens. He also reported that in some 

 instances it was possible to infect chickens by placing material containing the 

 agent either on the conjunctiva or on the rectal mucosa, but that inoculation 

 into the anterior chamber of the eye was without efi'ect. Wakamatsu used but 

 a small number of experimental birds and his experiments should be repeated 

 with larger groups of animals in order to verify these points. Hamilton and 

 Sawyer (92) reported that application of infective leukotic material to scarified 

 mucosa of the cloaca failed to produce the disease. When the material was 

 introduced into the bursa of Fabricius 20 percent of the inoculated birds developed 

 leukosis. 



The amount of whole blood or plasma necessary to reproduce the disease in a 

 susceptible fowl may be very small. Furth (73, 74) has successfully infected 

 chickens with 0.000001 cc. of blood plasma or 0.00001 cc. of cell suspension. 

 Engelbreth-Holm (48) likewise found 0.00001 cc. of leukemic blood capable of 



