42 CONTROL SERIES No. 63 



Data concerning the 9 chicks which reacted either to one or to both agglu- 

 tination tests and bacteriological examinations are shown in the following table: 



5. pullorum was isolated from 6 of the 9 chicks whose sera showed agglutinins. 

 5. pullorum was isolated from 7 chicks which did not react to either one of the 

 tests. The 2 controls were negative to both of the tests and to bacteriological 

 examination. 



Group II consisted of 21 chicks. At the ages of 7 and 10 days 2 chicks died and 

 5. pullorum was isolated from both. The remaining 19 and 5 controls of the 

 same age were killed on the fourteenth day. A slight reaction to both tests was 

 shown by 1 chick, and S. pullorum was not isolated. In a second chick agglutinins 

 were indicated to be present by the tube test, but not by the whole blood test, 

 and 5. pullormn was isolated. To both agglutination tests, 17 chicks were nega- 

 tive, and S. pullorum was isolated from 7. The 5 controls were negative to both 

 of the agglutination tests and to bacteriological examination. 



PART IV 



A group of 52 day-old chicks was exposed to artificial infection. Up to 4 

 weeks of age, 20 died and 5. pullorum was isolated from each chick. Beginning 

 at 4 weeks of age, the chicks were tested by the tube agglutination test at weekly 

 intervals. Dilutions of 1:10 and higher, sufficient to determine the titer, were 

 employed. A chick whose serimi produced partial, incomplete, or complete 

 agglutination in a dilution of 1:20 or higher was considered to be a reactor. 

 Immediately upon detection, reactors were isolated in individual cages, and the 

 pen was cleaned thoroughly. On the first test 6 reactors were detected. Reactors 

 appeared at each test up to and including the test made at 11 weeks of age. No 

 additional reactors appeared at later tests. A total of 24 reactors was detected 

 among the 32 chicks. 



Observations concerning 23 chicks made during the period between the fourth 

 and fifteenth weeks are shown in Table 14. 



S. pullorum was isolated from 6 non-reactors and 1 of 3 reactors which died. 

 At the age of 11 weeks it was necessary to kill 2 chicks, and at the age of 15 

 weeks 12 males were killed. Of these 14 chicks, 10 were considered to be reactors 

 and 4 non-reactors at the time of necropsy. Among these 4 non-reactors, 3 

 (Nos. 26, 33, and 41) had been considered to be reactors at earher tests. 5. 

 pullorum was isolated from 3 reactors among these 14 chicks. 



Observations were continued on the 8 reactors (pullets) and 1 non-reactor 

 (a cockerel) beyond the fifteenth week. The cockerel was negative to the tube 

 agglutination test up to 6J^ months, at which age it was killed, and 5. pullorum 

 was not isolated. The 8 pullets were to be retained in individual cages until 2 

 months after sexual maturity was attained. (A pullet was considered sexually 

 mature when it laid its first egg.) Table 15 contains observations and data 

 concerning the 8 pullets. 



