124 EVANS : BACILLUS ABORTUS IN MARKET MILK 



appreciable amounts of acid. Five per cent bile added to or- 

 dinary media favors growth. Several cultures which have been 

 isolated from milk were sent to Dr. Lothe, of the University of 

 Wisconsin, who reported positive reactions to the complement 

 fixation test in the presence of B. abortus amboceptor. 



In a study of the bacteria of the udder samples of milk which 

 were drawn aseptically have been examined from four herds. 

 Out of the samples of milk taken from 14 cows of one herd, B. 

 abortus was shown to be present in the milk from 5 of the cows, 

 in numbers up to 50,000 per cubic centimeter. Samples of 

 milk were taken from 40 cows of another herd. These cows 

 are under the constant supervision of a veterinarian, and it is 

 the aim of the dairyman in charge to supply to the institution 

 which owns the herd milk equal to that from the best certified 

 dairies. B. abortus was shown to be present in two out of the 40 

 samples; in both of which cases there were about 4,000 of these 

 bacilli per cubic centimeter. It is almost certain that the 

 results obtained from the milk from these two herds falls short 

 of showing the actual number of B. abortus present, for this 

 pB,rt of the study was made before the method which favors the 

 isolation of this organism was perfected, as described above. 



Samples of milk from two certified dairies in another region were 

 studied according to the method given. Out of 22 samples 

 taken at one of these dairy farms, 7 were shown to contain B. 

 abortus in numbers ranging from 180 to 800 per cubic centi- 

 meter. Out of 24 samples taken at the other dairy farm, 7 were 

 shown to contain B. abortus in numbers ranging from 110 to 

 4,300 per cubic centimeter. Considering together all the samples 

 taken at these two certified dairies, 14 out of 46, or about 30 

 per cent, were shown to contain B. abortus. 



Two bottles of certified milk were purchased in market, kept 

 at room temperature for about six hours, and then plated on the 

 serum agar. About 28,000 of the abortion bacilli were shown 

 to be present in the cream layer of one sample, and about 1,900 

 in the cream layer of the other sample. In both samples the 

 number of B. abortus was about 25 per cent of the whole number 

 of bacteria. 



A simple experiment was planned to show whether the iJi- 



