ABORTION 303 



The actual tests are made by preparing a uniform sus- 

 pension of the cells of the causal organism in a salt solu- 

 tion. A small quantity of blond is drawn from each ani- 

 mal to be tested, the blood is allowed to clot, and the serum 

 removed, which is then added in varying proportions to the 

 suspension of bacterial cells. If the blood is free from the 

 specific agglntinin produced by the animal on invasion by 

 ;he organism of abortion, the cells remain in suspension. If 

 the specific agglntinin is present, the cells clump and the 

 masses soon settle, leaving a clear liquid. The agglutinin 

 can be developed only as the host has been invaded by the 

 organism. A positive test does not imply that the animal at 

 the moment the blood was drawn was harboring the organ- 

 ism, for the anti-bodies persist Ion- after the organism has 

 disappeared from the body. Similar tests are used in the 

 detection of typhoid fever in man, glanders in horses, and 

 white diarrhea in chickens. 



A test for another of the anti-bodies is also used in the 

 detection of animals that are or have been affected with 

 B. abortus. The test is so complicated that it can not be 

 described here. It is similar to the Wassermann test used 

 for the detection of syphilis in humans. It is also known 

 as the complement fixation test. It involves the use of the 

 blood corpuscles or serum from three different species of 

 animals other than the bovine animal that is being tested. 

 The organism causing the disease is also used. It is an 

 example of the progress that has been made in the detection 

 of the most minute quantities of specific substances of un- 

 known nature formed by the bod}' cells of an animal in- 

 vaded by a parasitic organism. 



The stock-owner must rely for protection very largely 

 on the information he can secure as to the health of the 

 herd from which he intends to purchase. 



Control and prevention. It is not usual for an animal 



