110 Microscopic Histochemistry 



(such as in oleic and cinnamic acids) may react. However, 

 this is denied by Verne^^ and Oster and Oster,^^ who find 

 that a positive reaction is always due to contamination by 

 products of oxidation. 



Gerard^^ and Verne^^ made the observation that the same 

 lipid structures which stain positively with Schiff's reagent 

 also show strong oxidative properties, e.g., they recolorize 

 leuco-bases and stain intensely blue with the nadi-reagent, al- 

 though the intensity of the aldehyde and oxidative reactions 

 need not run parallel. This interesting observation may be 

 explained by the invariable compresence of aldehydes and 

 peroxides; furthermore, there is a possibility that part of the 

 color obtained in the Schiff reaction is due to a pseudo-reac- 

 tion: the oxidative recolorization of the reagent. However, 

 differentiation should be easy; the true aldehyde color is ex- 

 tremely resistant to acids, whereas regenerated fuchsin is 

 readily decolorized by them. 



Histochemical methods for lipid aldehydes 



1 ) For pre-formed aldehydes.— The best method is to use 

 fresh, unfixed frozen sections. However, a few hours' fixation 

 in formalin, followed by thorough washing in repeated 

 changes of distilled water, is permissible, although the stain- 

 ing of some structures (e.g., myelin sheaths) may be greatly 

 weakened. ^^ Freshly boiled distilled water should be used to 

 make up the formalin solution and to rinse the sections. 



Stain in Schiff's reagent ( straight or diluted with an equal 

 volume of distilled water) for about 30-60 minutes. Rinse 

 sections in a 1-3 per cent solution of Na bisulfite for a few 

 minutes. Rinse in repeated changes of tap water. Counter- 

 stain with hematoxylin. Mount either in glycerin-jelly or, 

 after dehydration, in balsam. The fatty aldehyde-Schiff com- 

 pound is lipid-insoluble. 



80. Veme, J.: Ann. de physiol., 5:245, 1929. 



81. Gerard, P.: Bull, d'histol. appliq. a la physiol., 12:274, 1935. 



82. Veme, J.: Compt. rend. Soc. de biol, 133:75, 1940; Verne, J.: Bull, 

 d'histol. appHq. a la physiol., 13:433, 1936. 



83. Veme, J.: Bull, d'histol. appHq. a la physiol., 14:269, 1937. 



