190 Microscopic Histochemistry 



In addition to the drfferences tabulated, it appears that 

 the ratio 



Hydrolysis of phenylphosphate 

 Hydrolysis of glycerophosphate 



is very much higher for the enzyme of red cells than for that 

 of the plasma.^* 



The original histochemical method^^ for acid phosphatase 

 utilizes the hydrolysis, of glycerophosphate at pH 5 in the 

 presence of Pb++ ions. Fixation in cold acetone and em- 

 bedding in paraffin are recommended. 



The results of this technique are not nearly so satisfactory 

 or consistent as, those of the method for alkaline phospha- 

 tase. A number of papers complaining of its capriciousness 

 and unreliabihty have been published. ^^^^ 



When the causes of failures are analyzed, they are found 

 to fall into six groups. 



1. Inactivation of the enzyme in the course of fixation, 

 embedding, storage, and incubation. There can be no doubt 

 that only a relatively small fraction of the enzyme survives 

 fixation and embedding. Inactivation may be fairly uniform 

 or peculiarly patchy; the boundary between active and inac- 

 tive areas is often quite sharp. Wolf, Kabat, and Newman^^ 

 find that a layer at a certain distance from the surface of the 

 block shows the best preservation of the enzyme. The writer 

 is under the impression that embedding and not fixation 

 (provided that cold acetone is used) is the main offender; 



64. Behrendt, H.: Proc. Soc. Exper. Biol. & Med., 54:268, 1943; Gutman, 

 E. B., and Gutman, A. B.: Proc. Soc. Exper. Biol. & Med., 47:513, 1941; 

 Gutman, E. B., and Gutman, A. B.: J. Clin. Investigation, 17:473, 1938; 

 Herbert, F. K.: Biochem. J., 38:23, 1944; King, E. J., W^ood, E. J., and 

 Delory, G. E.: Biochem. J., 39:24, 1945. 



65. Gomori, G.: Arch. Path., 32:189, 1941. 



66. Moog, F.: Proc. Nat. Acad. Sc, 29:176, 1943. 



67. Hard, W. L., and Lassek, A. M.: J. Neurophysiol., 9:121, 1946. 



68. Montagna, W., Nobaclc, C. R., and Zak, F. G.: Am. J. Anat., 83:409, 

 1948; Tissieres, A.: Acta anat., 5:224, 1948. 



69. W^olf, A., Kabat, E. A., and Newman, W.: Am. J. Path., 19:423, 1943. 



