P /euro-Pneumonia oj Cattle. 17 T 



should be noted, however, that the opalescence present in 

 any of the cultures was extremely slight, and after the addition 

 of serum and saline to the culture in the test, it was practically 

 impossible to recognise any opalescence at all. In consequence of 

 that fact, there was very little basis for comparing one tube with 

 another, in order to note whether there had been any clearing, 

 of the fluid in the tubes. 



Even if complete agglutination of all the organisms present 

 in any tube were to take place, it is certain that the resulting 

 deposit of agglutinated micro-organisms would be very slight 

 indeed, and it is possible that it might not be easily recognisable 

 as a deposit, particularly when no information can be obtained 

 from an examination of the fluid for clearing. 



An agglutination test was again set up, using as test sera Nos. 

 3 (positive) and 17 (negative). An alteration was made in the: 

 total quantity of the ingredients in the series of tubes, 1.5 c.c.s.. 

 of culture being taken as the standard amount of culture for each: 

 tube. The other ingredients were added to each tube in their 

 proper quantities, viz., the quantities used in the first test. These: 

 tubes were also placed in the incubator at 37°C. for 24 hours,, 

 then examined, and then allowed to stand at room temperature 

 for a further period of 16 hours, and again examined. There 

 was no recognisable agglutination in any tube in either series,, 

 and altogether the result was exactly similar to that obtained 

 with the test of sera Nos. 7 and 8. 



Simultaneously with the test of sera Nos. 3 and 17, another 

 test was set up, the sera used being Nos. 30 and 17. Serum No. 

 30 was obtained from Calf 1, an experimental animal used at the 

 Veterinary Research Institute, and one which had reacted to- 

 a subcutaneous inoculation in the tail of virulent serosity, taken 

 from the lungs of an active case of pleuro-pneumonia. This 

 calf had subsequently received a subcutaneous inoculation of 

 5 c.c.s. of virulent serosity behind the shoulder without any ex- 

 tensive swelling being produced. Later, it had received 15 c.c.s. 

 of an 8 days' old pure culture of the organism in Martin's broth 

 ox serum subcutaneously behind the other shoulder without any 

 swelling or tissue change being produced at the site of inocula- 

 tion. It was therefore assumed that Calf 1 had acquired a con- 

 siderable degree of immunity against the inoculation of virulent 

 pleuro-pneumonic material. For the test with this serum a 

 second subculture 22 days old, in Martin's broth ox serum was 



13 



