THE desirability of a suitable method of serological diagnosis for the avian leukosis complex has long been recognized. Numerous investigations have shown that there is an antibody response in fowls to the agent of avian leukosis. (Johnson, 1945; Olson 1945; Lee, 1942; Kabat and Furth, 1940). However, as yet no practi-cal method of detecting these specific antibodies has been developed. (Stafseth, 1941). It has been demonstrated that animals may produce antibodies against their own tissue, especially if there is a foreign agent closely associated with the tissue against which the antibody is formed. Investiga-tions have suggested that the agent of avian leukosis is closely associated with the blood cells because of the difficulty in obtaining filtrates which are as potent as whole blood. Agglutinins against human white blood cells have been demonstrated by means of tube leukoagglutination and used to dif-ferentiate various types of leukemia.

inches high, leaving an opening four by three inches through which a chicken may feed. Either heavy wires, the ends of which are soldered to the top of the wide walls, or one-inch mesh screen may be used at the top of the feed can. When the can is emptied, feed can be readily poured out through these large openings; yet an ob-struction is provided which prevents waste of feed by the chicken. A partition three and one-half inches high is located two inches from the front wall of the can, dividing the can into two compartments. If the bird scatters feed out of the feed compartment at the back of the can, the feed which otherwise would be wasted drops into the front compartment and is saved. The feed compartment is easily filled with a scoop three and one-half inches wide and nine inches long, and hav-ing two-inch sides. For convenience in weighing feed, a counter balance—equal in weight to the combined weight of the scoop and the feed which is to be placed in the can—is placed on the left balance pan, and feed is weighed directly into the scoop on the right pan. When the feed which is not eaten is weighed back, the weights on the The filtrable agents of chicken leukosis and sarcoma have been sedimented and concentrated by centrifugation (Stern and Kirschbaum, 1939; Kabat and Furth, 1940; and Gottschalk, 1946); however, similar treatment of the agent or agents producing lymphoid tumors or visceral lymphomatosis has thus far not been re-ported. Working with a rapidly growing trans-arni of a Harvard trip balance indicate directly the amount of feed which has been consumed.

Until recent years, very little was known concerning virus metabolism or the source of materials used by viruses for metabolic purposes, and physical and chemical methods were used mainly for the characterization of virus particles. These methods have contributed a great deal to our knowledge of viruses. However, some later investigations on influenza virus, mouse pneumonitis virus, and Rous sarcoma virus have shown that purified preparations of these agents may contain antigens and chemical substances of the normal host tissue, bound, perhaps chemically, to other substances characteristic of the virus alone.2 ' 9, 14, 19,20 These results suggest a need for re-interpretation of earlier chemical analyses of the various viruses. Recently, certain investigators have turned their attention to the study of the metabolism of viruses. Thus, for example, studies of the enzyme content of various virus preparations have shown that the viruses themselves probably are incapable of carrying out the necessary metabolic reactions for production and utilization of energy. This leads to the conclusion that the host cells must furnish such enzymes.28 Price,21 22'24 working with Staphylococcus muscae and a bacteriophage to which this strain was susceptible, has attempted to demonstrate growth requirements of bacteriophage through additions of specific medium components to penicillin-inhibited bacteria. Specific enzyme poisons have also been used by some investigators, such as Price,23 Fitzgerald and Lee,12 and Fitzgerald and Babbit,11 in attempts to clarify problems of bacteriophage metabolism. Cohen and Fowler7 have concluded as a result of their investigations that the synthesis of tryptophane is necessary for the growth of T2 bacteriophage. They further concluded that tryptophane need not be present as a component of the host's external environment but must be present in the environment to which the virus is exposed. These investigators have