PROPERTIES AND METHODS OF IDENTIFICATION 245 



i 



iodine. Dolley and Guthric (1919) have studied carotinoids in animal 

 tissues by means of fat stains with results which bear on this ques- 

 tion. They observed that amorphous deposits of what appeared to 

 be pure lipochrome in both animal and plant (carrot) tissues still 

 stained with Sudan III and Scarlet Red after the pigment granules 

 had become bleached through oxidation. This fact does not prove 

 that the pigment granules were not pure pigment, but it does throw 

 doubt upon this conclusion. Kreibich (1920) takes the view that the 

 lipochromes in animal tissues, which he calls sudanophiles, are united 

 with alcohol insoluble lipoids. 



Dolley and Guthrie (see also Palmer and Kcmpster (1919bj) made 

 the interesting observation that Nile blue (used either as the hydro- 

 chlorate or sulfate in 1-10,000 aqueous solution or as a stronger so- 

 lution in 65 per cent acetone) when used as a progressive stain, 

 "particularizes the lipochrome first as a deep blue," but stains neu- 

 tral fat a salmon pink even in the presence of lipochrome. The blue 

 stain w r as found to occur for the amorphous carotin granules in the 

 frozen carrot section, and for the amorphous xanthophyll granules 

 and minute pigment globules in the stratum corneum of the chicken 

 skin, while the salmon pink color occurred for lard stained deeply 

 with carotin from carrots, for chicken fat highly colored with xan- 

 thophyll, for the globules in colostrum milk fat, deeply colored with 

 carotin, and for the fat globules in the natural emulsion of the deep 

 yellow (xanthophyll colored) yolk of the hen's egg. Dolley and 

 Guthrie later (1921) found that the lipochrome granules of the heart 

 muscle stained blue with the dye, although in their earlier (1919) 

 work they were unable to secure positive differentiation of lipo- 

 chrome and fat in nerve cells by this method. 



These findings appear, at first sight, to be a definite advance in the 

 technic of demonstrating carotinoids in animal tissues. This conclu- 

 sion is weakened, however, by the fact that Smith (1907) showed that 

 Nile blue differentiates fatty acids from neutral fats in the same man- 

 ner that it appears to differentiate carotinoids from neutral fats, fatty 

 acids staining blue and neutral fat red. 1 This fact alone, however, 

 would not necessarily disprove the supposition that carotinoids may 

 act like fatty acids towards Nile blue, although it must be admitted 



1 Herxheimcr (AbderhaMrn's Handbuch dcr Biologischen Arbeltsmethoden, viil, part 

 1, 208) states that this fact has been confirmed by Escher (Korrbl. f. Schweizer Arzte, 

 1ft, 1919) and by Boeminghaus (Ziegter's Beit rage, 67, 532, 1920) who found also that 

 cholesterol esters of fatty acids stain red like neutral fat, and many other lipoids take 

 a mixed blue and red color. 



