4 MASS. EXPERIMENT STATION BULLETIN 295 



chicken to be immunized was inoculated in the wing vein with 1 cc. of fresh in- 

 fectious laryngotracheal exudate which had been diluted with physiological saline 

 and filtered through Seitz filters. In Group 1 the filtrate was diluted 1-10, and in 

 Groups 2, 3, and 4 the dilutions were 1-25, 1-50, and 1-100, respectively. The 

 eight controls were inoculated intratracheally with the filtrate as diluted for each 

 group. The results of the intravenous inoculations are reported in Table 1 . 



Table 1. — The Titration of Infectious Laryngotkacheitis Virus for 

 Intravenous Inoculation 



A study of Table 1 will show that dilutions 1-10, 1-25, and 1-50 were too strong, 

 since 14 chickens contracted the disease in Group 1, 12 in Group 2, and 4 in Group 

 3. The 1-100 dilution was too weak, for both controls were unaffected. 



All of the chickens surviving the intravenous inoculations were inoculated in- 

 tratracheally with fresh infectious laryngotracheitis virus. The results are given 

 in Table 2. 



Table 2. — The Results of the Intratracheal Inoculations of the Chickens 

 Previously Inoculated Intravenously (Table 1). 



The data in Table 2 show that the four chickens in Group 1 and the seven 

 chickens in Group 2, affected by the intravenous inoculations, were immune to 

 infectious laryngotracheitis. The unaffected chickens in Groups 1 and 2 were 

 immune also. Three of the 11 unaffected chickens in Group 3 contracted infec- 

 tious laryngotracheitis without fatal termination, while the two affected chickens 

 were found to be immune. Seven of the fifteen chickens unaffected by the intra- 

 venous inoculations in Group 4 were affected by the intratracheal swabbings and 

 one died. 



One of the control chickens in Group 3, Table 1, was affected by the intratra- 

 cheal inoculation and the other was not. In Table 2 these chickens are reversed 

 as a result of the intratracheal swabbings. Both of the chickens in Group 4 

 contracted infectious laryngotracheitis and died, indicating that the virus had 

 been diluted too much, as was suspected. 



