114 Microscopic Histochemistry 



groups is unsubstituted. Arginine is the only compound found 

 in tissues which will give a positive reaction. 



Of the several modifications published/ Baker's is rela- 

 tively the simplest and most reliable. 



Method 



Use celloidin sections or paraflBn sections protected with 

 collodion. The thickness of the sections should be at least 



10 ;x. 



Mix rapidly 2 ml. of 1 per cent NaOH, 2 drops of a 1 per 

 cent solution of a-napthol in 70 per cent alcohol, 4 drops of 

 a 1 per cent solution of Na hypochlorite ( a dilution of Clorox 

 or of some similar household bleaching agent with 7-10 parts 

 of water ) . Pour mixture on the slide immediately and leave 

 it on for 15 minutes. Drain fluid off the slide, blot it, and 

 immerse it in a mixture of 3 parts of pyridine and 1 part of 

 chloroform. Mount in the same medium. Arginine-containing 

 proteins stain in an orange-red shade. The full intensity of 

 the color is permanent for a few hours only. Clearing in 

 xylene and mounting in balsam is permissible, but fading of 

 the color will be even faster. 



3. The xanthoprotein reaction^ is specific for aromatic 

 rings, which are nitrated by cold fuming nitric acid to yield 

 yellow dyes. 



4. Diazonium salts will couple with phenols and hetero- 

 cyclic rings^ (tyrosine, histidine, proline, etc.) to yield yel- 

 lowish or brownish azo dyes of low color intensity. 



5. Syrupy phosphoric acid, especially with a trace of some 



7. Serra, J. A.: Port, acta biol., 1:1, 1944; Serra, J. A.: Naturwiss., 32:46, 

 1944; Thomas, L. E.: J. Cell. & Comp. Physiol., 28:145, 1946; Baker, J. R.: 

 Quart. J. Micr. So., 88:115, 1947; Thomas, L. E.: Stain Technol., 25:143, 

 1950; Warren, T. N., and McManus, J. F. A.: J. Nat. Cancer Inst., 12:223, 

 1951. 



8. Raspail, F. V.: Nouveau systeme de chimie organique (3d ed.; Brussels: 

 1840), 1:161. 



9. Pauly, H.: Ztschr. f. physiol. Chem., 42:508, 1904; Brunswik, H.: 

 Ztschr. f. physiol. Chem., 127:268, 1923; Berg, W.: Arch. f. d. ges. Physiol., 

 199:656, 1923. 



