BACILLUS ABORTUS 191 



may be used or an agar gelatine serum mixture (4 per cent 

 gelatine, 6 per cent agar and 1 per cent serum) the serum in 

 which is previously heated to 60° C. for one hour on 4 con- 

 secutive days to ensure sterility. This latter mediiun is very 

 satisfactory for shake cultures. In carbohydrate media slightly 

 variable results are recorded. Most workers report that neutral 

 carbohydrate broths remain neutral or are rendered slightly 

 alkaline, except for a few cultures which produce sUght acidity 

 in dextrose. Good and Corbett ^ report that B. abortus variety 

 equinus showed an average of 2 per cent of gas in lactose in 93 

 cultures and no gas in 23. In saccharose 58 gave a httle less 

 than 2 per cent of gas and 28 were negative. Some cultures 

 also produced marked quantities of gas in xylose, dextrose, 

 arabinose, dulcite, sorbite, mannite, maltose, and rafl&nose. 

 Duphcate and triplicate tests with lactose and saccharose gave 

 varying results but Good and Corbett are convinced that the 

 gas produced is the result of chemical action and not adven- 

 titious. From the results of the fermentation tests, these 

 workers place the equinus variety in the Gaertner group of 

 organisms. The great difference in fermentative ability be- 

 tween this variety and the other members of the B. abortus 

 group would appear to warrant a change ui the nomenclature 

 of the equinus variety and its removal from the abortus group. 

 In guinea pigs, milk containing B. abortus often produces a 

 nodular condition of the spleen and liver, the macroscopical 

 appearance having a somewhat superficial resemblance to that 

 produced by B. tuberculosis. In pregnant test animals, inoc- 

 ulation with cultures usually produces abortion in a few days 

 but in some cases the action is much delayed and in others the 

 gestation period may be quite normal. 



ACID-PHODUCING ORGANISMS 



Although the organisms found in mUk capable of fermenting 

 lactose with the production of acid include such widely differ- 

 ing groups as diplococci, staphylococci, streptococci, and bacilU, 



