DISEASE, INFECTION, AND EESISTANCE 295 



ered from typhoid fever. It is possible also to produce 

 antisera containing specific bacteriolysins in the horse, for 

 example, and to use such antisera in the treatment or pre- 

 vention of disease. The serum used in the treatment of the 

 disease cerebrospinal meningitis usually contains consider- 

 able amounts of bacteriolysin specific for the meningococcus, 

 the organism v^hich causes this disease. 



Complement Fixation in the Diagnosis of Disease. — In 

 certain diseases amboceptors specific for the causal micro- 

 organism are formed early. Their development does not 

 necessarily mean the recovery or effective immunization of 

 the patient. This is particularly true in certain chronic 

 infections. For example, the disease glanders in the horse 

 may and frequently does assume a chronic form which is 

 not at all readily recognized by clinical examination. 

 Whether or not the animal has the disease, however, may be 

 determined by examining a sample of the blood for the 

 presence or absence of the amboceptors specific for the 

 glanders bacillus. If they are present it is usually consid- 

 ered as conclusive evidence that the animal has the disease 

 glanders. This test, that is, hunting for specific ambo- 

 ceptors in the blood of suspected individuals, is termed the 

 complement fixation test. Two groups of substances are 

 necessary. The first is that group required for the specific 

 reaction, and second, a group used as an indicator for the 

 recognition of the reaction. 



The materials of the first group are as follows : 



1. Suspension of specific organisms such as glanders 

 bacillus (the antigen). 



2. Serum from the animal, such as the horse, suspected 

 of having the disease. — If the disease is present this serum 

 will contain amboceptor and complement. The latter is 

 removed, however, before the test by heating. A positive 

 test will mean the presence of an amboceptor specific for 

 the glanders bacillus. 



