Enzymes 177 



results obtained with nucleic acids and with diesters of phos- 

 phoric and pyrophosphoric acid as substrates (in the case 

 of the last two substrates, by the azo dye technique, p. 184) 

 are indistinguishable from those seen with the use of glyc- 

 erophosphate,^^ for example. There is no histochemical indi- 

 cation of the presence of diesterases or pyrophosphatases in 

 paraffin-embedded animal tissues. 



According to Emmel,^^ renal phosphatase and intestinal 

 phosphatase in the mouse can be differentiated from each 

 other by their markedly different sensitivities to cyanide and 

 acid. His findings have been verified,^^ but, since they do not 

 apply to species other than the mouse,^^ they must not be 

 interpreted as an indication of a general difference between 

 renal and intestinal phosphatase. 



In view of the conflicting findings and opinions, the prob- 

 lem of the presence of several substrate-specific alkaline 

 phosphatases in embedded tissues requires critical re-ex- 

 amination. 



Friedenwald and CrowelP^ and Maengwyn-Davies and 

 Friedenwald^^ found, by the use of various substrates and 

 activators, that fresh unfixed tissues contain substrate-spe- 

 cific phosphatases which cannot be demonstrated in fixed 

 tissues. This appears to be an important discovery which 

 deserves thorough investigation. 



Technical details.— 



Freshness of the tissue is not a very important factor. Good 

 results may be obtained with refrigerated tissue fixed as late 



22. Gomori, G.: Unpublished. 



23. Emmel, V. M.: Anat. Rec, 95^59, 1946; Emmel, V. M,: ibid., 

 96:423, 1946; Emmel, V. M.: ibid., 103:445, 1949; Emmel, V. M.: J. Nat. 

 Cancer Inst., 10:1365, 1950; Emmel, V. M.: Proc. Soc. Exper. Biol. & Med., 

 75:114, 1950; Emmel, V. M.: Anat. Rec., 106:270, 1950. 



24. Gomori, G.: Ann. New York Acad. Sc, 50:968, 1950. 



25. Friedenwald, J. S., and Crowell, J. E.: Bull. Johns Hopkins Hosp., 

 84:658, 1949. 



26. Maengwyn-Davies, G. D., and Friedenwald, J. S.: J. Nat. Cancer Inst, 

 10:1379, 1950. 



