500 INFECTION AND IMMUNITY. 



or even as high as 1-6000. Agglutinins develop 

 fairly early in the course of the infection, and the 

 test is of great diagnostic importance. They dis- 

 appear in about two years after recovery (Birt and 

 Lamb ) . 



Bacillus melitensis, discovered by Bruce (1887) 

 in the spleen of patients who had died of the dis- 

 ease, is a minute organism, slightly oval in shape. 

 According to Gordon, it possesses one flagellum, 

 rarely two or four, and is slightly motile. The 

 bacillus is found in pure cultures in the spleen, 

 which is greatly enlarged. Its growth in culture 

 media is very slow. 



It is thought that infected water may be one 

 means of transmission of the disease. Laboratory 

 infections with pure cultures have occurred 

 through small wounds resulting in typical attacks 

 of Malta fever (Birt and Lamb). The disease is 

 not transmitted from person to person. 



Up to the present time the monkey is the only 

 animal known with susceptibility to artificial infec- 

 tion, although the organism has a certain viru- 

 lence for rabbits and guinea-pigs on intraperito- 

 neal or intracerebral injection (Durham). 



One attack confers immunity, which may disap- 

 pear, however, after some time (Hughes). 



An immune serum which was prepared by 

 Wright is said to influence favorably the course of 

 the disease. 



