Nuclei blue-black; cell-inclusions yellow- to copper-red. =V. CHOLESTERIN.= Cholesterin is soluble in absolute alcohol, xylol, ether and glacial acetic. It occurs in the tissues in characteristic rhombic plates often showing a square notch in one corner. In sections from which the cholesterin has been dissolved its presence may be told by the appearance of “cholesterin-clefts” in the tissue, or often in the protoplasm of large foreign-body giant-cells (“cholesterin-giant-cells”). With concentrated sulphuric acid, sections or material containing cholesterin become yellow and then rose-pink. Lugol’s gives it a brown color which turns blue-violet after the addition of sulphuric acid, and exhibits a play of colors, blue, green, to red. =VI. CLOUDY SWELLING.= This is best seen in the fresh state in cells obtained by scraping or teasing, or by the examination of frozen sections. Osmic acid, sudan III, scarlet R. ether, alcohol and acetic acid may be used to differentiate from fatty degeneration. The ordinary fixing and staining methods give good pictures, except for slight degrees of the change. These are sometimes wholly lost as the result of the contraction due to the fixation. =VII. COLLOID.= (See Epithelial Hyalin.) =VIII. CORNIFICATION.= Horn takes the plasma stains (eosin, picric acid, etc.). Van Gieson’s makes a good differential stain. With Gram’s method horn stains deep blue, and with the Ehrlich-Biondi-Heidenhain method it stains red. After fixation in Flemming’s it may be stained with safranin or gentian-violet. =Keratohyalin= occurs as fine granules in the cells of the stratum granulosum. They stain by hæmatoxylin, carmine and Gram’s method, or may be demonstrated by means of special stains. =Eleidin= stains with carmine and the fat-stains, but not with hæmatoxylin. 1. =Buzzi’s Method of Staining Eleidin and Keratohyalin.= 1. Harden, imbed, cut. 2. Stain in Congo red (2-3 drops of a 1 per cent water solution added to small basin of water) for 2-3 minutes. 3. Wash thoroughly in water. 4. Stain in hæmatoxylin, and wash. 5. Dehydrate in absolute alcohol; xylol; balsam. Keratohyalin blue, eleidin red. 2. =Fick’s Method of Staining Keratohyalin and Keratin.= 1. Harden in alcohol, imbed, cut. 2. Stain in saturated water solution of kresyl-echt-violett for 3-4 minutes. 3. Wash thoroughly in water. 4. Differentiate in 95 per cent alcohol until connective-tissue is colorless. 5. Dehydrate in absolute alcohol; xylol; balsam. Keratohyalin red, keratin dark violet; nuclei blue-violet, plasma light blue-violet.