IMMUNOLOGY OF LARYNGOTRACHEITIS 7 



Group 2 was treated in the same manner with 2 cc. of the tracheal exudate solution, 

 diluted 1-25 and filtered through a sterile Seitz filter, and Groups 3 and 4 were 

 inoculated with two and three doses of the same liquid at weekly intervals. Groups 

 5 and 6 were treated with tracheal exudate which had been diluted 1-25 in saline 

 and glycerol mixed in equal volumes. 



Table 5. — The Results of Subcutaneous Inoculations of Infectious 

 laryngotracheitis virus 



Table 5 shows that the chickens in Groups 1,2,3, and 4 were not as well pro- 

 tected as those in Groups 5 and 6. Also, it shows that the virus which was inocu- 

 lated intratracheally was virulent, for all of the controls died. Obviously the 

 degree of immunity imparted by subcutaneous inoculations is relative, depending 

 upon the virulence of the virus, the number of inoculations, and the viscosity of 

 the fluid injected. 



Since the farmer with whom the field project was carried on felt that three or 

 more inoculations, involving as many handlings of the birds, was a serious draw- 

 back, the study of the subcutaneous method was abandoned as being impractical 

 under range conditions. 



TISSUE VACCINES 



The success of Boynton (1928), Kelser (1928), and Nakizaki et al. (1926) with 

 tissues vaccines for rinderpest, the experiments of Laidlaw and Dunkin (1927, 

 1928) with distemper in ferrets and dogs, and Pasteur's rabies vaccine suggest 

 that possibly a similar biologic might be developed for infectious laryngotracheitis, 

 since Gibbs (1931) and Beach (1931) report finding the virus associated with the 

 tissues of diseased chickens. However, before attempting any vaccinations it was 

 deemed best to approach this project by studying the constancy, the virulence, 

 and the preservation of the \'irus in the tissues as compared with that in the trachea 

 of the same bird. 



By careful manipulation all three points were determined in one experiment as 

 follows: 



Twelve chickens, six weeks old, were placed in cages, so that they could be 

 observed and handled better than if allowed to run in a single large room, or colony 

 house. The chickens were inoculated intratracheally with fresh tracheal exudate, 

 and every other day beginning the second day after the inoculation two of the 

 chickens were killed and the liver, spleen, blood, and tracheal exudate removed 

 under aseptic conditions and placed in sterile mortars. The tissues were pounded 

 and rubbed into smooth masses with sterile pestles. Sufficient saline was added 

 to yield a 20 per cent suspension of tissue pulp, and after brief stirring the contents 

 of the mortars were transferred to sterile bottles containing glass beads. The bottles 



