EVANS: BACILLUS ABORTUS IN MARKET MILK 123 



series of complement deviation tests with the blood of children 

 in which the abortion bacillus was used as an antigen. 



So far as the writer is aware, no bacteriological methods have 

 been described by which B. abortus can be demonstrated in milk, 

 and no data have been reported to show the numbers of these 

 organisms which may be present. Therefore, a detailed de- 

 scription of a method by which B. abortus may be isolated from 

 milk and identified may be useful at this time. 



The milk is plated on ordinary lactose agar, to which there is 

 added just before pouring into the plate, at a temperature of 

 about 50°C., 10 per cent of sterile blood serum. After incu- 

 bating for four days at 37°C., a certain area of the plate, large 

 enough to include several colonies of B. abortus, should they be 

 present, is selected, and the colonies are transferred to a nutrient 

 broth containing 1 per cent of glycerine. Colonies from a 

 similar area are transferred to tubes of whole milk containing 

 litmus. The growth in the glycerine broth is quite characteris- 

 tic: There is a medium amount of growth in tiny, compact, 

 spherical masses which settles to the bottom of the tube and does 

 not cloud the broth. In litmus whole milk there is an abundant 

 growth in the cream layer, with a gradual development of acid. 

 Cultures in litmus milk from which the cream has been removed 

 grow sparingly, with no apparent effect. On plain infusion 

 agar slopes the growth is in very small, separate colonies, which 

 are scattered over the whole surface of the slope, if it happens to 

 be moist at the time of inoculation; or the colonies are confined 

 to a ribbon-like growth along the line of inoculation, if the agar 

 is comparatively dry when inoculated. 



Cultures which were isolated by the above method agreed in 

 all essential points with the descriptions of B. abortus found in 

 the literature. This organism is a small rod-shaped bacterium 

 about 0.5 M in width, and with a length sometimes of 3 fx. But 

 the cells are often so short as to appear almost coccoid in form. 

 Growth in ordinary media is very sparing or may not take place. 

 The carbohydrates and Velated substances which many bacteria 

 ferment are not attacked, with the exception of glycerine, which 

 serves as a food, but is not broken down with the formation of 



