256 PATHOGENIC BACTERIA IN MILK 



the injection after three to fifteen days. Similar changes to the 

 above have occurred, but of a more intense degree. Rabinowitsch 

 found rabbits insusceptible in contrast to guinea-pigs. It is not 

 known whether this bacillus is in any degree pathogenic for man. 

 But probably such is not the case. It appears to be widely distri- 

 buted in nature, as 60 per cent, of butter samples in Berlin were 

 found to contain it. The only satisfactory way to differentiate 

 this bacillus from the true bacillus is by inoculation of animals. 



Obermiiller, Moeller, Korn, and others have isolated very 

 similar organisms to the bacillus of Rabinowitsch from milk or 

 milk products. Korn's bacillus of butter is said to differ in 

 morphology, cultivation, and pathogenic action from the Petri- 

 Rabinowitsch bacillus. All these acid-resistant bacilli obtained 

 from milk or its derivatives show a close resemblance to another 

 group of organisms to which brief reference must be made. Some 

 authorities, indeed, maintain that the two groups are really varieties 

 of a common species. 



Acid-fast bacilli in grass, hay, and manure. — This second 

 group of acid-fast bacilli associated with milk (marked {d') in the 

 classification above) is often designated as the grass bacilli. They 

 were first cultured on Timothy grass {^Phleuni pratense), which is 

 much valued for feeding cattle.^ Since then, however, this grass 

 bacillus has been found in various places, and it or its allies have 

 been isolated from cattle fodder, hay, hay-dust, manure, milk, and 

 its derivatives. Morphologically, this bacillus is similar to the 

 tubercle bacillus, slender and slightly curved. It contains highly 

 stained granules ; oval, clear spaces ; often grows in threads ; and 

 is branched, and sometimes has club swellings at one end. It is 

 acid-fast in staining, and grows best at incubation temperatures on 

 the ordinary culture media. The colonies become visible in thirty- 

 six hours, are scale-like and greyish-white in colour. Under certain 

 conditions its growth in artificial media is very similar to the 

 tubercle bacillus, which however does not thrive at room tempera- 

 ture. As regards pathogenic properties, the grass bacillus is almost 

 identical with the Petri-Rabinowitsch butter bacillus in its effects 

 on guinea-pigs. It has somewhat different effect on rabbits, pro- 

 ducing a condition difficult to distinguish from true tuberculosis 



^ Cafs-tail or Titnothy grass {Phleum pratense). Flowers, June to August. 

 Spikelets, one-flowered, and arranged in spicate manner. Although well known 

 to the British grower this grass is more extensively cultivated in the United 

 States, where it was introduced from Britain, nearly a century ago, by Mr 

 Timothy Hanson, after whom it is named Timothy grass. 



