Organic Substances 103 



Dissolve 50 mg. of hematoxylin in 48 ml. of distilled water, 

 add 1 ml. of a 1 per cent solution of potassium iodate, and 

 heat it to a boil. Cool, add 1 ml. of acetic acid. 



7. Rinse sections, differentiate in a 0.25 per cent solution 

 each of borax and of potassium ferricyanide for 18 hours at 

 37° C. 



8. Wash and mount in glycerin-jelly. 



Lecithin, cephalin, and sphingomyelin stain in an intense 

 blue-black shade. Only this shade is diagnostic; other un- 

 saturated lipids may stain in shades of brown and gray. A 

 few nonlipid substances, such as mucin and hemoglobin, will 

 stain in the same shade as the phospholipids. As a control. 

 Baker suggests the extraction of an adjacent tissue block, 

 fixed in Bouin's solution, with pyridine at 60° C, and run- 

 ning it through the same schedule. Since this treatment re- 

 moves all hpid, whatever is stained is nonlipid. The differ- 

 ence between the two blocks is due to phosopholipid only. 



Valade^^ recommends a different scheme of extraction and 

 chromation; its specificity for phopholipids, has not been 

 tested. 



Chromated tissues can also be embedded in paraffin and 

 stained with Sudan dyes, preferably Sudan black B. This 

 method does not differentiate clearly between phospholipids 

 and other unsaturated fats, although the former (since they 

 chromate faster and are rendered insoluble more readily) 

 will stain more intensely. Quantitative preservation of any 

 type of lipid cannot be expected. 



c) Alsterberg^^ proposes the demonstration of phospho- 

 lipids by a different principle. The reagent consists of cyan- 

 ogen iodide and silver nitrate ^ ( or chlorate ) . According to 

 the author, choline and colamiae decompose cyanogen iodide 

 and cause the precipitation of a mixture of silver cyanide 

 and iodide which can be visualized in a second step. This 

 method requires further investigation; neither the soundness 



47. Valade, P.: BuU. Acad. vet. France, 22:77, 1949. 



48. Alsterberg, G.: Ztschr. f. Zellforsch. u. mikr. Anat., 31:364, 1940-41. 



