184 G. G. Heslop: 



The marked turbidity of the concentrated culture made it pos- 

 sible to still recognise some turbidity in the tubes when the neces- 

 sary amounts of serum and saline were added, so that, in these 

 tests with concentrated culture, it was possible to compare the 

 fluid in the tubes for any clearing which might take place dur- 

 ing the test. Excepting with the tubes containing Serum No. 

 30, no clearing of the test fluid occured, and no agglutination 

 could be demonstrated when serum from a naturally infected 

 animal was mixed with a culture of the filter passing organism 

 isolated from a case of contagious pleuro-pneumonia. 



The failure to obtain a recognisable agglutination reaction with 

 this concentrated culture when mixed with the sera of naturally 

 infected animals made us abandon the agglutination test as a 

 potential diagnostic reaction for the detection Jof contagious 

 pleuro-pneumonia in the living animal. 



Ability of the Organism to Grow in Media containing 

 Immune Sera. 



On the conclusion of these aggultination tests it was decided 

 io try if the addition to the culture medium of serum from natur- 

 ally infected and from experimentally inoculated animals would 

 influence the growth of the organisms when subcultures were 

 made into such media. For this experiment, three separate 

 "batches of media were prepared. The first consisted of Martin's 

 Peptone Broth plus 7.5 per cent, of Serum No. 27, which was 

 obtained from a naturally infected animal. The second consisted 

 of Martin's Peptone Broth, plus 7.5 per cent, of serum No. 30, 

 which was obtained from Experimental Calf 1. The third con- 

 sisted of Martin's Peptone Broth plus 7.5 per cent, of normal 

 <ox serum. 



Several tubes of each batch of medium # were inoculated from a 

 primary culture of the organism in Martin's broth plus normal ox 

 serum. Growths took place in all the tubes inoculated. In the 

 tubes containing Serum No. 27 (from a naturally infected ani- 

 mal) the characteristic opalescence was observed four days after 

 inoculation and incubation at 37°C, and on comparison with the 

 tubes of Martin's broth, plus normal ox serum, inoculated at the 

 .■same time from the same source, no difference in the degree of 

 opalescence, or in the general appearance of the cultures could 

 t>e observed. On comparing the cultures containing the serum 

 from Experimental Calf 1 with those containing Serum No. 27, 



