550 



Journal of Applied Microscopy. 



A Convenient Micro-Polariscope for Food Examination. 



The value of the micro-polariscope as a means of distinguishing starch 

 granules from other bodies and starch granules of different plants from each 

 other, does not appear to be fully recognized by some of the leading authorities 

 on the microscopy of foods, chief dependence being placed on the iodine test, 



the shape and size of the granules, 

 the form and location of the hilum, 

 and the character of the concentric 

 rings. 



While it is true that the skilled 

 microscopist can distinguish the 

 various starches when illumined by 

 ordinary light, still if he is provided 

 with a suitably arranged polaris- 

 cope, he can often reach his con- 

 clusions, with a saving of both 

 time and eyesight. 



Among the authors who advo- 

 cate the use of this apparatus may 

 be mentioned Tripe, Blythe, Rich- 

 ardson, and McGill. 



The classification of starches 

 adopted by Blythe^ is based on the 

 appearance of the granules with 

 polarized light and the selenite 

 plate. Richardson 2 illustrates the 

 application of the polariscope in 

 the examination, with reference to 

 adulteration, of ground spices and 

 condiments. McGilF describes its 

 use in the quantitative determina- 

 tion of wheat flour in ginger. 



The writer has found polarized 

 light of special service in the ex- 

 amination of sausage for potato. 



Fig. I. 



wheat, and maize flour, which are frequently added to this food as carriers of 

 water. If the fat is not removed before examination, the colorless starch 

 granules are not readily distinguished from the fat globules, and the fat also 

 interferes with the iodine test, but with crossed prisms the starch not only 

 becomes evident, but the particular variety present may be readily determined. 

 One of the chief drawbacks to the use of this appliance is that biological 



1. Foods. Composition and Analysis. Fourth Edition, p. 170. 



2. U. S. Dept. of Agriculture, Div. Chem., Bull. 13, Part II. 



3. This journal, Vol. i, p. 51. 



