ABSTRACT
The yolk titre of eggs laid by hens actively immune to Salmonella pullorum is directly related to the serum titre, the concentration quotient being approximately 1/8.
Fowl sera immune to S. pullorum or Brucella abortus when injected into the yolk-sac early in incubation give rise to circulating titres in the chick at hatching.
A technique of injection into the yolk-sac after hatching is described. Immune fowl serum so injected gives rise to circulating titres.
Immune rabbit, cow, and horse sera so injected do not give rise to circulating titres. Immune pigeon serum gives rise to titres at lower concentration quotient than fowl. It is concluded that the yolk-sac splanchnopleur is selective.
Fowl antibody fed by mouth after hatching does not give rise to circulating titres.
