76 DISEASES OF DOMESTICATED BIRDS 
Fic. 5. Normal ovary. (Redrawn from Rettger, Kirkpatrick and Jones) 
has been hatched from eggs from a particular flock of hens is proof 
enough of infection in the flock, providing that there is a reasonable 
certainty that contamination has not been introduced by outside 
sources or from infected incubators or brooders. Detection of the 
characteristic pullorum-infected ovaries, on post mortem examina- 
tion, is definite proof that the disease is prevalent in the flock. Bac- 
Fic. 6. Ovary infected with B. pullorum. (Redrawn from Rettger, Kirkpatrick 
and Jones) 
