were divided into two groups and one group was revaccinated. Chicks were 

 hatched from each group and found immune on an adequate challenge. Addi- 

 tional chicks weje selected from each group and one half were vaccinated 

 with live virus wing web vaccine at two days of age and the others were not 

 vaccinated. Upon challenge at the age of five weeks the chicks were found 

 to possess no immunity. 



This experiment was repeated with known susceptible and known im- 

 mune breeders with identical results. Field checks on 150,000 birds vacci- 

 nated as chicks by the modified live virus web vaccine also indicated no 

 immunity at seven weeks. 



W. R. Dunlop 



47 



