THE MICROSCOPE AS DETECTIVE 



greater the quantity of starch. Some parts of the 

 bread will be stained yellow, this indicates the 

 presence of another nourishing component of bread. 

 Certain kinds of bread are supposed to contain no 

 free starch, because this substance is not beneficial 

 to some people. Iodine again will reveal whether 

 the bread is as it is described, for, if there be no 

 free starch there will be no blue colouration. Brown 

 bread will show much more of the yellow coloura- 

 tion and less of the blue than white bread. Good, 

 well-baked bread should keep for a considerable 

 period without turning sour; we can easily see 

 whether our sample is satisfactory by running a 

 drop of litmus on to it and watching the effect under 

 the microscope; if the litmus remains unchanged 

 in colour the sample is not sour; if, on the other 

 hand, the litmus turns red it shows us that acid 

 is present and that our bread is not as it 

 should be. 



Tea is difficult to prepare for microscopic examina- 

 tion and most of the tests call for expert knowledge, 

 not only in the management of the microscope but 

 of the plant itself. The structure of the leaves can 

 be made out clearly in specimens which have been 

 soaked for a time in water, but this is of little in- 

 terest to the ordinary microscopist. One very pretty 

 test may, however, easily be performed. We all know 

 that it is not good to drink tea which has been 

 standing for a long time. Some tea-drinkers are so 

 particular that they cannot bear to see the teapot 

 shaken before they have poured out their cup. All 



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