Contagious or Epizootic Abortion in Cows. 99 
If any importance is to be attached to the results, the tube 
containing plain emulsion, and all the tubes containing emulsion 
and serum from the non-inf ected animal, must be unaltered in 
appearance. Furthermore, the three tubes from the animal 
known to have been infected must show distinct agglutination, 
the evidence of which will be that the liquid in the tubes has 
now become quite clear owing to settlement of suspended 
bacilli to the bottom. Assuming that the things have worked 
Fig. 4.— A series of four tubes containing serum from a suspected cow. Agglutination 
has been complete in the left hand tube, nearly complete in the next, and distinct 
though less in the third. No agglutination has taken place in the fourth (right hand) 
tube. 
The agglutination proves that the suspected cow .was actually affected with 
contagious abortion. 
out in this way, one is nowiable to judge whether the suspected 
animal whose serum is being tested is an infected animal or 
not. In the former case some or all of the tubes will show 
complete agglutination, whereas if the animal has not been 
infected no agglutination will have taken place, and the tubes 
will show just the same appearance as when they were placed 
