BACILLUS BULGARICUS 157 



Of the acid-forming bacilli in milk we have i. the B. lactls acid group. These are 

 oval cells about 0.9 microns by 0.6 microns, often in chains. They are Gram- 

 positive and nonmotile. They may be the same as Streptococcus lacticus of Kruse. 

 They curdle milk with a homogeneous clot this being due to the fact that they do 

 not produce gas in lactose media. 2. The B. coli aerc genes group. These are gas 

 producers. (See under water.) 3. The B. bulgaricus group. In connection with 

 the organisms present in the tablets used for treating milk to produce lactic acid for 

 the treatment of intestinal disorders, and considered to be normal lactic acid bacteria, 

 I have found both streptococci and bacilli. These have all agreed, however, in not 

 producing gas in either lactose or glucose fermentation tubes. 



I have often found the commercial fluid cultures sterile, the great 

 acidity produced by B. bulgaricus causing this. Fresh tubes may show 

 an acidity of +12 or about 10 times that of ordinary culture media. 



The organism upon which special stress is laid in these so-called lactic acid pro- 

 ducers is the B. bulgaricus. This is a large, nonmotile organism with square ends 

 like anthrax. It often occurs in long chains and does not possess spores. It is Gram- 

 positive and often shows metachromatic granules like those of the diphtheria bacillus. 

 Colonies show in forty-eight hours which resemble streptococcus ones, but are more 

 contoured on the surface. Magnified the colonies resemble young mould colonies 

 It grows better on milk agar plates than on whey agar plates. The opacity of the 

 milk agar plate is but a slight objection. It produces a deep vivid pink in litmus 

 milk, while milk streptococci only cause a light pink. It produces a very large 

 amount of acid (3%). Little or no growth on ordinary laboratory media or bejow 

 oC. (Op. temp. 42C.). 



Heinemann states that it occurs normally in human faeces and various fermented 

 milks also in gastric juice when HC1 is absent. To isolate, put milk or faeces into 

 a broth containing 0.5% acetic acid and 2% glucose. Transfer to litmus milk after 

 twenty-four hours and from such tubes plate out on milk serum agar (coagulate 

 boiling milk with a few drops of acetic acid, filter and add i% peptone, 2% glucose 

 and 1.5% agar). 



As they grow in very acid media the term acidophilous is applied. It was sup- 

 posed that these bacteria were peculiar to certain fermented milks as matzoon and 

 yogurt. Hastings has shown the group to be present in milk in the United States 

 and considers the source to be the alimentary tract of cows. 



Milk Leukocytes. Another source of information as to the quality 

 of a milk may be derived from a study of the number of leukocytes or 

 pus cells contained in i c.c. of the milk. It must be understood that 

 cellular elements which differ only slightly from true pus cells may be 

 found in the milk of healthy cows and may be found in great numbers. 

 Statements have been made that such cells are neither amoeboid nor 

 phagocytic. 



The Doane-Buckley method is probably the most accurate. In this you throw 

 down the cellular contents of 10 c.c. of milk in a centrifuge revolving about 1000 



