PRACTICAL APPLICATIONS 277 



In cholera the agglutination test has so far proved of doubtful aid in 

 establishing a diagnosis of the disease. However, for the purpose of 

 recognizing bacilli isolated from the feces of suspicious cases the reaction 

 with known immune serum is of great value. 



In cerebrospinal meningitis the agglutination occurs within an hour 

 in dilutions of 1 : 10. It is seldom that the patient's serum agglutinates 

 in a dilution higher than 1 : 50. 



In tuberculosis the agglutination reaction has no value as a diagnostic 

 procedure. Koch recommended the agglutination test for the estima- 

 tion of the degree of immunity conferred by tuberculin treatment. As 

 pointed out elsewhere, agglutinins have apparently no antimicrobic 

 influence, but, as with typhoid vaccination, may indicate the degree of 

 reaction and the presence of other antibodies. 



Many strains of tubercle bacilli are almost non-agglutinable. The 

 preparation of a homogeneous emulsion is not easily made, and the results 

 are likely to be confusing and contradictory. 



In plague the agglutination reaction becomes quite marked about 

 the ninth day of the disease too late, however, to be of much practical 

 value in diagnosis. It is occasionally useful, however, for deciding 

 whether a patient in the convalescent stage has really suffered from the 

 disease. 



In Malta fever the agglutination reaction is of considerable value in 

 making the diagnosis. 



In pneumonia the reaction is of value in rapidly differentiating pneu- 

 mococci and as an aid in specific serum therapy, and it may also be of aid 

 in making the diagnosis of infection with Bacillus enteritidis and Bacil- 

 lus botulinus. 



In veterinary practice agglutination reactions are of value in the 

 diagnosis of glanders, infected horses reacting in some instances to dilu- 

 tions as high as 1:2000. For diagnostic purposes the agglutination 

 test in glanders must be in dilutions higher than 1:800. A positive 

 reaction in dilutions of 1:1000 is regarded as suggestive, and is con- 

 trolled by a complement-fixation test; agglutination in dilutions of 

 1 : 1500 practically always indicates an infection. The complement-fixa- 

 tion test, however, is a better diagnostic reaction. 



2. Agglutination reactions are also of value as an aid to the identi- 

 fication of a microorganism that has been cultivated from a patient. 

 For this purpose we must have on hand various standard immune 

 serums. For example, if a bacillus resembling the typhoid bacillus is 

 isolated from the feces of a patient, the diagnosis may be aided by a 

 positive agglutination reaction with typhoid immune serum. 



