SPECIAL EXAMINATIONS 369 



Tubercular Disease of the Udder of Cows. Milk. During 

 the year (1910) 227 samples of milk from 225 cows with 

 suspected disease of the udder were examined, 53 of which 

 gave positive results, giving an average of 23-5 per cent. 

 From the beginning of February, special attention has been 

 given to the examination of smear preparations, in order that 

 an immediate report might be given, instead of waiting three 

 weeks for the animal inoculation test. Out of 44 specimens 

 so examined, 31 were found positive. The milk in each case 

 was stopped within two days of the taking of sample. 



It might here be mentioned in connection with the examina- 

 tion of smear preparations, that an elaborate and complicated 

 process of staining is not necessary, as a good result does not 

 depend so much on the process of staining, as the time spent 

 on the examination of the film. The method now adopted 

 is the ordinary Ziehl-Neelson, the film, after discoloration, 

 being well washed in absolute alcohol to clear it up. 



All the samples giving negative smears were subjected to 

 the animal inoculation test. 



Twenty-seven samples of milk were obtained from four of 

 the positive cows, for the purpose of ascertaining whether 

 the " fore," " mid," or " strippings " milk contained the 

 most bacilli, also whether the bacilli were more numerous in 

 the cream than in the deposit. The samples were taken by 

 the County Veterinary Surgeon. 



In each case the whole of the milk from the affected quarter 

 was drawn off in separate consecutive samples, the last one 

 always containing the last drop of milk procurable. 



Each specimen when received was centrifugalized for 15 

 minutes, and smear preparations made with one platinum 

 loopful of the cream and of the deposit. The loopful was 

 then thoroughly mixed on the slide and spread over an area 

 the breadth of the slide and one inch in length. The films 

 were stained by Ziehl-Neelson's method. The count, which 

 of course was an approximate one, was carried out by running 

 the t l oil immersion lens straight across the centre of the 

 film, counting the bacilli in each field and multiplying the 

 total by twelve. (The film being an inch in length and the 

 lens used ^). Where the bacilli were few in number, the whole 

 film was examined and counted. The results obtained were 

 as shown in the table on following page. 



It will be seen from the results obtained from Cows I., II., 

 and IV., that the " mid " milk was richest in bacilli, and 

 would evidently be the proper part to take when such a milk 

 was to be examined, more especially by smear preparation. 

 No reliance could be placed on the samples taken from Cow 

 No. III., as the milk was too small in amount. 



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