ANNUAL REPORT, 1930 281 



domestic and senii-doniestic animals. Approximately 15 per cent of al! 

 poultry examined were infested with jiarasites, led by coccidiosis, witli 

 tapeworm infestation second. Avian tuberculosis was diagnosed on two 

 farms. Fowl cholera and fowl typhoid were not encountered. 



An especially virulent strain of S. puUorum was isolated from mature 

 stock and studied. This cidture was i)hysiologically and serologically iden- 

 tical to stock strains of S'. palluriim. It ])roduced death in two birds in- 

 jected intravenously with 0.2 cc. of broth culture in 17 and 18 days, 

 respectively, and the organism was again recovered. Two birds inoculated 

 intratracheally with 0.5 cc. of broth culture were made visibly sick for a 

 period of a week, but recovered. The primary lesion produced in these 

 cases was a pericarditis. 



A group of 25 day-old chicks were fed mash, which was contained in 

 a bag contaminated with S. pullorum, for a period of three weeks. No 

 mortality occurred from pullorum disease. At six weeks of age the 

 agglutination test revealed two reactors. No more reactors were detected 

 by the agglutination test applied at one and two weeks intervals over .a 

 period of se^■en months. S. pullorum was isolated from one of the two 

 original reactors wjiich were detected at the age of six weeks. 



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

 project, has recorded 1330 agglutination tests. 



Infectious Trachitis in Poultry. (C. S. Gibbs). Progress has been made 

 in the study of infectious trncliitis. The disease has been found to be 

 caused by a filtrable virus. The virus has been demonstrated in tITe 

 tracheal exudate and in the secretions from the kidneys of diseased birds. 

 Some of the birds recovering from infectious trachitis have been found 

 to persist as apparently healthy immune carriers. The viability of the 

 virus is prolonged by freezing and drying. 



Studies on secondary invaders in infectious trachitis have been made, 

 and a laryngo-tracheal spirochete has been discovered. As far as is 

 known at this station, this microorganism has not been observed before 

 in poultry in the United States. 



Details of these investigations are being prepared for publication. 



THE WALTHAM FIELD STATION 



(Waltham, Massachusetts) 



Ray M. Koon in Charge 



For reports on experiments conducted at this substation in addition to 

 these listed under the Waltham Field Station, see reports of the Depart- 

 ments of Botany, Entomology and Floriculture. 



The Plant House. (P. W. Dempsey). Experiments have been continued in 

 the construction, heating and operation of a sash-covered plant house. A 

 twelve-sash hotbed was added to the plant-house model and one hot-water 

 heater was used as a source of heat for both. This arrangement proved 

 more satisfactory than using horse manure for hotbed heat. The interest 

 in the plant house is indicated by the fact that 500 copies of plans and 

 specifications have been sent out in response to requests for information. 



