EXPERIMENT STATION BULLETINS. 283 



STUDIES IN INFECTIOUS ABOETION. 

 The Isolatiou of Bacterium ahortus from Milk. 



Part IV. 



I. FOREST HUDDLESON. 



INTRODUCTION. 



The role which infected udders play in disseminating the abortion 

 bacillus has been studied by a number of investigators. It now becomes 

 apparent to those familiar with infectious abortion, that the control and 

 prevention ol this disease will depend largely upon the early diagnosis 

 and bacteriological supervision of temporary or potential carriers. The 

 occurrence and continued presence of Bact. dhortus in milk coming from 

 apparently normal cows are now established facts, and furnish us a very 

 important carrier problem. 



In order to study successfully the occurrence of Bact. abortus in milk, 

 the knowledge and application of reliable methods which will permit the 

 isolation of the infecting organism is absolutely necessary, regardless 

 of the number present. The methods employed by previous investi- 

 gators in studying the presence of Bact. abortus in milk have their dis- 

 advantages and have not been entirely successful. Fabyan (1) and 

 Schroeder (2) working independently demonstrated the presence of 

 Bact. ahortus in milk by means of guinea pig inoculation. This method 

 is reliable but has a disadvantage in that it takes from eight to ten weeks 

 for the characteristic lesions to develop, and a large number of guinea 

 pigs is necessary when a number of milk samples is to be studied. 

 Cooledge (3) studied the presence of Bact. abortus in milk by means of 

 the agglutination test. This method is not wholly satisfactory owing 

 to the fact that a positive reaction to the agglutination test does not 

 always indicate the presence of the organism. Evans (4) in studying 

 samples of milk from a large number of cows, by employing cultural 

 methods, failed to isolate Bact. ahortus from the milk of cows which had 

 aborted as a result of natural infection. She succeeded, however, in 

 isolating the organism from the milk of cows which had aborted as a 

 result of feeding and injecting cultures of the organism. This is readily 

 explained from the fact that strains of the organism which have been 

 cultivated upon artificial media may be recovered from inoculated ani- 

 mals without employing anaerobic methods. 



EXrERI MENTAL WORK. 



In the isolation of Bact. ahortus from milk the most perplexing diffi- 

 culty usually encountered is the elimination of other organisms which 

 may be present in considerable numbers thus over-growing the inocu- 

 lated media. 



In order to render the isolation and cultivation of Bact. abortus from 



