108 PRINCIPLES AND PRACTICE OF MILK HYGIENE 



numbers in the sediment and cream, especially the poly- 

 morphonuclear leucocytes in purulent catarrh. The 

 catalase content is increased. Coagulation occurs when 

 the alcohol or the boiling test (see pages 284, 285) is 

 applied. 



On account of the difficulty of detecting catarrhal 

 mastitis in its early stages, the determination of the leuco- 

 cytic content of samples of market milk has sometimes 

 been relied on to discover the presence of the disease. It 

 has been demonstrated that cases of catarrhal mastitis 

 may be detected by this method but we have no means of 

 knowing how many of such cases escape discovery; there 

 is reason to believe that many are overlooked. The ex- 

 amination of samples of milk from individual cows by 

 means of the catalase test is the most efficient method of 

 detecting the disease (see page 287). When numerous 

 very small, punctiform, brownish colonies appear in the 

 plates prepared for determining the number of bacteria in 

 milk and these are found upon microscopic examination to 

 consist of streptococci in long chains, an examination of 

 the herd will usually discover the presence of one or more 

 cases of catarrhal mastitis. 



A special form of purulent catarrhal mastitis which 

 leads to multiple abscess formation is caused by the Bacil- 

 lus pyogenes. The secretion has a foul odor. The disease 

 occurs most commonly in " dry " cows, but is usually not 

 discovered until they become " fresh." 



2. Parenchymatous Mastitis. The detection of this 

 form of mastitis offers no difficulties to the dairy inspec- 

 tor. It is attended with an immediate and pronounced 

 swelling of the affected portion of the udder and the milk 

 at once presents marked changes. As the name indicates, 

 it is an inflammation of the alveoli and small tubules of 



