1894.] MICROSCOPICAL JOURNAL. 211 



Osmic acid colors oil drops in the protoplasm black or 

 deep brown. Sections may be put in a 1 per cent solu- 

 tion, or be exposed to osmic vapor after fixing by picric 

 acid. Wash, mount in glycerine. 



To stain the basic substance, guinolein blue is best. 

 To a porcelain saucer of filtered water add a few drops 

 of an alcoholic solution of the blue. The water at once 

 becomes beautifully light blue with an iridescent sur- 

 face, due to a precipitation of some of the coloring mat- 

 ter. In a certain time the water becomes decolored, the 

 blue granules falling to the bott'om. The water should 

 not be too deeply colored. The sections, when entirely 

 freed from picric acid, should remain there for a few 

 hours. Wash carefully ; mount in neutral glycerine. 

 The cells are stained blue, the hyaline substance a beau- 

 tiful violet. In preparations thus stained, and treated 

 with the 40 per cent potash solution, we can obtain a 

 blue color in the fat granules within the cell protoplasm. 



Cartilage with branching cells from the head of a 

 cephalopod may be studied in sections after fixing by 

 picric acid. Stain with piero-carmine. . . . 



Elastic cartilage should be studied in sections of the 

 epiglottis of man or of the dog. A portion is fixed in 

 picric acid for 24 hours, hardened in alcohol, embedded 

 in gum ; longitudinal sections are made and put into 

 water. When freed from the yellow color, stain in 

 picro-carmine, wash, mount in water, and allow to run 

 under the cover a drop of the following, as suggested 

 by Ranvier for the study of arteries : — glycerine, 50; 

 saturated solution of picric acid, 50 ; formic acid, 1. 



To study fibro-cartilage, section the semi-lunar cartil- 

 age of the knee ; treat with picric acid, alcohol, gum. 

 Stain with picro-carmine. 



BONY TISSUE. 



Two kinds of preparations should be made, one from 



