70 THE BACTERIOLOGICAL EXAMINATION OF MILK 



tubes or cylinder containing freshly prepared mixture of pyrogallic 

 acid and potassium hydrate solution. Seal the Buchner tubes or 

 cylinder with great care, making it absolute. Place the Buchner 

 apparatus, including the milk tubes, in the incubator at 37" C. 

 After forty-eight hours take out the tubes, and examine them for 

 the B. enteritidis sporogenes. If necessary inoculate guinea-pigs 

 subcutaneously with i c.c. of the whey, which in a few hours causes 

 swelling at the point of inoculation, and extensive gangrene of 

 the subcutaneous and muscular tissues with sanguineous exuda- 

 tion ; the animal dies in twenty-four or thirty hours. The B. 

 butyricus of Botkin may produce similar changes in milk tubes, 

 but it has no pathogenic action. Milk may be examined directly 

 by placing 20 c.c. in tubes and treating as above. The " enteri- 

 tidis change " in the milk thus treated consists in copious gas 

 formation, clear or slightly turbid whey in the middle of the 

 tube, with faintly pinkish flocculi of casein floating on top, and 

 casein masses at sides and bottom of tube. 



Bacillus tuberculosis- 

 Obtain the sediment of the milk under examination and 

 inoculate 2 c.c. of it into the subcutaneous tissue of a guinea-pig. 

 In about four weeks time, local, if not general, tuberculosis will have 

 been set up {see p. 74). Take some of the discharge and stain it 

 after the Ziehl-Neelsen method. The sediment of tuberculous 

 milk may be stained forthwith, without inoculation, by the same 

 method, and in some cases the tubercle bacillus may be thus 

 detected, but generally speaking the only sure test is inoculation 

 of animals. The pathological process is slower than in pseudo- 

 tuberculosis, and on examination the diseased tissues show giant 

 cells and numerous tubercle bacilli arranged within the giant cell 

 {see Plate 21). 



Differentiation between the tubercle bacillus and otJier acid-fast 

 bacilli. — For the differentiation of the bacillus tuberculosis from 

 other acid-fast organisms in butter the only reliable method is that 

 of inoculation. The following is the procedure employed in the 

 examination of butter as originally devised by Obermuller,^ and 

 subsequently modified by Rabinowitsch, Coggi, and others. The 

 butter under examination, received into a sterile conical glass, 

 with all aseptic precautions possible, is placed in the incubator 

 at 37° C, where on melting it will be found to arrange itself in 

 ^ HyS't Rundschau^ 1895, No. 19, p. 877, and 1900, No. 17, p. 845. 



