THE MICROSCOPE AS DETECTIVE 



in testing under the microscope— only very small 

 quantities are required. 



Butter can hardly be described as an interesting 

 object for the microscope, nevertheless, it may be 

 of use to explain the methods of its examination. 

 A small sample should be placed upon a clean slide, 

 a drop of olive oil added and the whole covered 

 with a cover slip which may be pressed firmly till 

 the specimen forms but a thin layer. Of course the 

 most important impurities likely to be present are 

 bacteria but these we cannot see without special 

 preparation and we are not dealing with bacteria 

 in the present chapter. 



If our specimen is in a film sufficiently thin to be 

 transparent, and we should have made it so by 

 pressure on the cover slip, we may first of all 

 examine it carefully for starch grains which, by the 

 way, should be absent. The amount and size of the 

 drops of water, which every butter sample contains, 

 are of importance in deciding its quality. In good 

 butter there are a few scattered drops of various 

 sizes; in milk-blended butter the water globules 

 are all very small and all of the same size, or as 

 nearly so as the eye can judge ; in butter containing 

 an excessive amount of water the drops appear large, 

 much larger than in a normal sample. 



If we examine various samples, we shall find that 

 some are much more transparent than others, the 

 transparent samples being fresh butter. The curd 

 also in fresh samples is much more finely and evenly 

 scattered in the field of view than in older samples. 



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