THE MICROSCOPE AS DETECTIVE 



usually grouped together in twos or threes; when 

 they rest on their flat surfaces they appear circular 

 and each hilum is surrounded by a dark ring, when 

 on their sides they are seen to be sugar-loaf 

 shaped. 



Many more starches can be found without going 

 far afield, Sago, Peas, Beans, Lentils and Bananas 

 are a few common commodities containing starch. 

 An effort should be made to study the very curious 

 dumbell shaped starch grains of the Spurge and its 

 relations. All these plants contain a white milky 

 juice in which the starch grains float; by squeezing 

 a little of this milky fluid into a drop of water on 

 a clean slide the grains can easily be observed. 



It is sometimes difficult to observe starch grains 

 till a fair amount of experience has been gained in 

 the use of the microscope. Should this difficulty arise, 

 it may be overcome by adding a drop of a weak 

 solution of iodine. This will stain the starch grains 

 a deep blue colour and render them very easy of 

 observation. The iodine solution must be weak, 

 however, or the staining will be excessive and the 

 objects rendered black and non-transparent. 



Having examined many or all of the specimens 

 we have mentioned let us turn our attention to some 

 of the common foods, and learn some of the methods 

 used in testing for impurities. Ordinary household 

 bread, it is hardly necessary to state, is rich in 

 starch and, by trying the iodine test, mentioned 

 above its presence is easily shown. With a weak 

 solution the deeper the blue colour produced, the 



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