28 MICRO-CHEMICAL REAGENTS. 



clearing fluid in the Hanstein and Russow meth- 

 ods of clearing tissues. A mixture of dilute potash 

 and glycerine has been employed by Hegelmaier in 

 the study of the embryo. 1 



Kraus has employed glycerine as a reagent for 

 sugar and inulin. When sections that contain 

 these substances in solution are placed in glyce- 

 rine, strongly refractive rounded drops appear in 

 the cells. If inulin is present these drops change 

 to the characteristic spaero-crystals, and remain ; 

 but if only sugar is present in the tissue they 

 rapidly dissolve again. The sections should not 

 be laid in water, but must be placed directly in the 

 glycerine. The reliability of this reaction is cer- 

 tainly worthy of further tests. With larger masses 

 of tissue, glycerine can also be used for the sepa- 

 ration of inulin, and it is a good preservative 

 medium for inulin preparations. 



lodin-glycerine is useful in the study of protein 

 grains. It is prepared by dissolving a little iodine 

 in glycerine, to which a small quantity of iodide of 

 potassium has previously been added. More spe- 

 cific directions as to the relative quantities are un- 

 necessary. 



Warm glycerine is also used for the same pur- 

 pose. In it the protein grains, which under natural 

 conditions are uniformly refractive, become differ- 



1 [For the use of glycerine in the cellulose test, see sulphuric acid, p. 16. 

 For its employment instead of potassium tartrate in Fehling's sugar test, 

 see cupric sulphate, p. 36. W. T.] 



