From infected material obtained from various herds virus has been isolated
in several instances in developing hen's eggs, and in one instance also in mice.
The strain which could be propagated in both mice and eggs was taken
25 generations by intracerebral passage in mice. In early passages day-old mice
were used but later passage was continued in adult mice. In these, mortality
occurred regularly after three to four days. Gradocol membrane filtration indicated
that the particle diameter was Jess than 100 mµ.
In developing hen's eggs this strain was propagated for twelve generations
by chorio-allantoic membrane passage. Definite lesions on the membrane were
observed and occasional embryos died. Subsequent passages were made by the
injection of infected embryo material into the yolk sac. In this way the virus
was readily maintained a further ten generations, at which stage it regularly killed all embryos.
Cows and heifers infected with material from both the mouse and egg
propagated lines of this strain showed definite, though mild, symptoms of
The possibility of various forms of vaginitis occurring in bovines as well as
the relation of this virus to these conditions is discussed.