42 Microscopic Histochemistry 



Zinc— Fair amounts of this element are known to occur in 

 the pancreatic islets ( as a component of insulin ) and in the 

 red cells (as a component of carbonic anhydrase). 



Mendel and Bradley"^^ have described a method based on 

 the insolubility of zinc nitroprusside. It has been applied 

 only to tissues of mollusks, which contain very large amounts 

 of zinc. 



Method 



Fixation not specified in original article; presumably alco- 

 hol or formalin would do. Treat paraffin sections for 15 

 minutes at 50° C. with a 10 per cent solution of Na nitro- 

 prusside. Wash under the tap for 15 minutes. Mount section 

 in water and let a drop of dilute potassium sulfide solution 

 run under the cover slip. An intense purple shade indicates 

 the presence of zinc. 



Okamoto^" suggests diphenylthiocarbazide as a reagent. 



Method 



Alcohol fixation. Prepare a saturated solution of diphenyl- 

 thiocarbazide in 60 per cent alcohol. Use solution when 2-4 

 days old. Add 1-3 ml. of this solution to 50 ml. of a borate 

 buflPer of pH 8.4-9.2. Stain sections in the mixture for 2-3 

 hours at room temperature. Rinse briefly in water. Counter- 

 stain lightly with hematoxylin; do not differentiate. Mount 

 in glycerol-jelly. Zn purplish red. Mercury gives a more 

 bluish-purple shade. 



This method has yielded good results in the rabbit pan- 

 creas ;*^'^* equivocal or poor ones in the pancreases of other 

 species.** 



Manganese.— GYund\a.nd and Bulliard*^ suggest the use of 



41. Mendel, L. B., and Bradley, H. C: Am. J. Physiol., 14:313, 1905. 



42. Okamoto, K.: Tr. Soc. Path. Jap., 32:99, 1942; and Okamoto, K., 

 and Hashimoto, M.: Taishitzu Gaku Zasshi, 13:83, 1944. 



43. Kadota, J.: J. Lab. & Clin. Med., 35:568, 1950. 



44. Gomori, G.: Unpublished. 



45. Grundland, I., and BuUiard, H.: Compt. rend. Soc. de biol., 142:201,^ 

 1948. 



