38 MICROSCOPIC TECHNIQUES 



1 % Sodium Nitroprusside. 

 Ammonium Sulfate Crystals. 



PROCEDURE 



1. Cover fresh tissue slice with 0.25 niL water. 



2. Add 0.05 ml. ammonium hydroxide and then 0.05 ml. of the 

 nitroprusside soln. 



3. Underline the tissue with 0.25 g. ammonium sulfate crystals 

 and examine at once. 



C. ORGANIC SUBSTANCES AND GROUPS 



LIPIDS AND CHOLESTEROL* 



By means of staining methods, it is impossible to distinguish 

 with certainty between the various chemical types of the lipids 

 with the possible exception of cholesterol and its esters. Until 

 recently, the demonstration of lipids in general was usually carried 

 out with Sudan dyes which dissolve in the lipids and color them. 

 However, Jackson (1944) reported an improved method using 

 acetic-carbol-Sudan III which he claims should supersede all other 

 Sudan methods since it will bring out lipids that have been con- 

 sidered refractory to Sudan staining in the past. Jackson's paper 

 includes an enlightening critical survey of previous work. To cir- 

 cumvent the loss of small fat globules from the tissue when alcohol 

 or acetone dye solutions are used, Telford Govan (1944) employed 

 Sudan dyes suspended in aqueous media. The Kay and Whitehead 

 ( 1935) procedure using Sudan IV, the newer Jackson ( 1944) method 

 employing acetic-carbol-Sudan III, and the Telford Govan (1944) 

 technique will be described. The staining of lipids by means of 

 fluorescent dyes according to Popper (page 105) would appear to 

 have some advantages, particularly in the use of the water-soluble 

 dyes such as Phosphine 3R. 



Cholesterol and its esters may be visualized by the Liebermann- 

 Burchardt reaction as adapted for histological use by Schultz ( 1924- 

 1925) , Romieu ( 1927) , and Yamasaki ( 1931) . The Schultz procedure 

 has been employed more generally, and hence it will be given in 

 detail. Lison (1936, page 210) has pointed out that, though the 

 positive test is specific, a negative result does not necessarily 



* See Bibliography Appendix, Ref. 3. 



