ANNUAL REPORT, 1931 241 



8. Dilvitc pulloruin antigen was divided into three equal parts. One part 

 was titrated to pH 8.4, one part to pH 7.2, and one part to pH 7.2, but raised to 

 Hp 8.4 at the time of each test. The antigens were stored at 8° C. and tested 

 at frequent intervals with five positive and five negative pullorum sera. Consis- 

 tent macroscopic antigenic differences were not observed among the antigens 

 over a period of fifteen weeks. 



9. Antigens were prepared monthly from three sets of cultures over a period 

 of 45 weeks. Two sets of cultures were transferred at monthly intervals, one 

 being retained at 8° C. and the other at room temperature (approximately 22° 

 C). The third set was transferred at weekly intervals and retained at room 

 temperature. Comparative tests of these antigens during this period revealed 

 no consistent antigenic macroscopic differences. 



10. S. pullorum was observed to remain viable on a dry piece of cloth in a 

 Kolle flask for 26 weeks. The viability observations are being continued. 



Laboratory Service — Pathology. (G. L. Dunlap). This service was used 

 by 311 persons, 92 of whom called either to deliver specimens or to discuss 

 poultry diseases. A total of 1,046 specimens was received. Parasitic infestations 

 continue to be the most frequent diseased conditions sent to the laboratory. 

 Avian tuberculosis, fowl cholera, and fowl typhoid were not encountered this 

 year. Carbon monoxide poisoning was diagnosed in two lots of chicks. 



B. aerytrycke infection has been found in a number of pigeon lofts and an at- 

 tempt is being made to eradicate the disease in one loft by means of the agglu- 

 tination test. 



A study was made of so-called "crazy chicks." The uric acid contfnt of the 

 blood of affected chicks was found to be two to six times greater than normal. 

 Epithelial degeneration of the kidney and proventriculus was the prominent 

 lesion. Details of this work were presented at the annual meeting of the Ameri- 

 can \'eterinary Medical Association (Kansas City, August, 1931) as Massachu- 

 setts Agricultural Experiment Station Contribution 125, "An Ataxia of Chicks 

 Associated with Nephritis." 



The causes of mortality in the Station flock are being studied in an effort to 

 minimize these losses. 



Farm and Station Bang's Disease. The laboratory, in assisting this 

 project, has recorded 966 agglutination tests. 



Infectious Laryngotracheitis. (C. S. Gibbs). Studies on chronic carriers 

 of infectious laryngotracheitis in poultry have been continued. Among 520 

 birds examined by direct swabbing of the trachea, 17 chronic carriers have 

 been found. The longest time a carrier eliminated virus was 378 days and the 

 shortest time was 14 days. Three of the chronic carriers have not yet completed 

 the carrier stage. Thirteen may be classified as constant and four as intermittent 

 in type. A more expedient test to detect chronic carriers is needed. 



Studies indicate that the most common channel of infection is the respiratory 

 tract. 



Pullets and cockerels, as well as adult birds, may be immunized bj^ intravenous 

 and subcutaneous inoculations of small doses of filtered virus over a long period 

 of time. No practical method for immunization of birds on a large scale is rec- 

 ommended. 



