24 MASS. EXPERIMENT STATION BULLETIN 370 



phenol solution but was inactivated by a 0.5 percent tannin solution according 

 to Jarmai (99). He believed that, in the latter case, the agent was bound to the 

 albumin molecule and precipitated with the tannin solution. More recently, 

 Jarmai (102) has submitted evidence to indicate that the agent in the blood of 

 leukotic chickens is more frequently bound with the globulin fraction than with 

 the albumin fraction of the blood. The disease produced with the prepared globulin 

 fraction was characterized by a prolonged incubation period, although the dura- 

 tion of the disease when once established was about 15 days. 



The leukosis agent is susceptible to oxidation as is indicated by the work of 

 Engelbreth-Holm and Frederiksen (53) and Rufiiilli (174 c). RuffiUi used gaseous 

 oxj'gen, hydrogen peroxide, and potassium, permanganate as oxidizing agents 

 whose destructive action could be hindered or prevented by the presence of 

 cystein, but could not be reversed. Engelbreth-Holm and Frederiksen (53) used 

 gaseous oxygen and found that leukotic plasma could be reactivated by cystein- 

 cobalt, if the oxidation were interrupted before inactivation was complete. 

 Rufhlli (174 c) obtained inactivation of leukotic plasma in the presence of normal 

 chicken erythrocytes when proper conditions of temperature and length of ex- 

 posure were supplied. Tissue cultures of normal adult spleen, liver, and bone 

 marrow likewise destroyed the agent in leukotic plasma used to nourish the 

 cultures. 



The agent of fowl leukosis has been shown to be resistant to irradiation with 

 roentgen rays by the investigations of Jarmai, Stenszky, and Farkas (105), 

 Engelbreth-Holm and Rothe Me^'er (54), and Forfota (67). Jarmai (103) has 

 discussed his own work and the work of others with respect to the resistance to 

 roentgen rays of the agents of leukosis, the agent of the Rous sarcoma, and the 

 filtrable agent of his own strain of sarcoma, and the cells of various transmissible 

 mammalian neoplasms. He has pointed out that the agents of the filtrable fowl 

 tumors and fowl leukosis will withstand an enormous dose of roentgen rays. 

 The Rous sarcoma agent has been exposed to 600 times the erythema dose and 

 the leukosis agent to 240 times the erythema dose without destruction. Frag- 

 ments of the mammalian tumors (Ehrlich's mouse carcinoma, the Moravek- 

 Jedlickas mouse carcinoma, a transmissible m.ouse sarcoma initially produced by 

 chemical action, and the Flexner-Jobling rat sarcoma) lost their infectivity after 

 exposure to only 20 erythema doses of roentgen rays. 



Wakamatsu (210) studied the effect of treatment of the leukosis agent with 

 a preparation called hepatrat, and the gold, silver, arsenic, and copper salts of 

 detoxin. The effect of such treatment was slight or none. Rothmann's plumbo- 

 dithio-pyridincarbonacid potassium and lead detoxin were found to have a distinct 

 inhibiting action on the agent of fowl leukosis. 



Rothe Meyer, Engelbreth-Holm and Uhl (172, 174) have shown that the agent 

 of leukosis present in the blood plasma may be bound to the red blood corpuscles 

 of normal and spontaneously recovered chickens as well as to the red blood 

 cells of pigeons, rabbits, sheep, and man. The corpuscles of such a mixture could 

 not be freed of the agent by repeated washing after the mixture had been allowed 

 to stand for one hour at room temperature. It was further found that ten con- 

 secutive adsorptions of leukotic plasma with red blood cells of a normal chicken 

 did not exhaust the leukosis-producing power of the plasma. They believed that 

 this combination of cells and agent was a matter of simple physical adsorption. 



Kabat and Furth (118 a) have reported studies on the properties of crude 

 extracts and high-speed centrifugate of the tumors produced by the Strain 13 

 agent and on the high-speed centrifugate of plasma obtained from birds made 

 leukotic with either Strain 13 or Strain 1 agent (see appended synopsis, p. 48). 



