628 STATE BOARD OF AGRICULTURE. 



A STUDY OF THE PRESENCE OF BACTERIUM ABORTUS (BANG) 



IN MILK. 



INTRODUCTION. 



While Bad. abortus (Bang), the organism that is generally thought 

 to be the causative bacterium of the disease of cattle called contagious 

 abortion was isolated by Bang in 189G, and his findings were later con- 

 firmed by other continental investigators, the organism was not isolated 

 in England until 1909 and not until 1911 in the United States. In that 

 year MacNeal and Kerr isolated from two cases of infectious abortion or- 

 ganisms which they regarded as identical with Bang's bacterium. 



They describe this organism as follows: "The organism is a very 

 small short rod, usually oval in shape, from 0.8 microns to 2.0 microns 

 long by 0.7 microns wide, practically always single, rarely in short 

 threads of two to four cells. It is not motile, and does not form spores. 

 It stains with moderate rapidity with the ordinary aniline dyes, and is 

 decolorized by Gram's method. The colonies on serum agar are raised, 

 with smooth circular borders, appearing almost like drops of dew. They 

 are transparent and very clear, with a bluish gray color by transmitted 

 light. Under the microscope a few coarse granules may be seen near the 

 center of the colony but the greater part of it appears very homogeneous 

 and almost water clear. The appearance of the colony is really a very 

 characteristic feature of the organism and enables one to distinguish 

 readily the colony of the abortion bacillus from other colonies on the 

 serum agar plates." 



Another characteristic of this organism that is of value as a means of 

 identification and that is largely responsible for the difficulty of isola- 

 tion is its relation toward oxygen. 



It has been shown that this organism when first isolated from dis- 

 eased tissues will not grow under aerobic conditions, or under anaerobic 

 conditions but requires an atmosphere partially depleted of oxygen. 

 This atmospheric condition may be obtained artificially by growing the 

 culture in a closed jar with a culture of Bacillus suMilis, one square 

 centimeter of fresh growth of B. suhtilis to each fifteen cubic centimeters 

 of jar capacity giving the proper oxygen tension. In agar shakes of 

 the newly isolated organism, growth will appear in a zone at a depth at 

 which the proper amount of oxygen is present. This is usually about 

 one cm. below the surface. 



In 1912 Melvin reported that Mohler of the Pathological Division and 

 Schroeder and Cotton of the Experiment Station of the Bureau of 

 Animal Industry had isolated an organism from milk which was identical 

 with the bacterium of infectious abortion. 



Schroeder and Cotton consider the most remarkable thing about this 

 organism to be its explusion from the bodies of apparently healthy 

 cows with their milk. They prove this to be a fact by repeatedly demon- 

 strating the presence of the organism in milk which had been collected 

 with the greatest care against outside contamination. Cows which had 

 previously been found to be infected were used. They also demonstrated 



