188 Microscopic Histochemistry 



formation and bibliography the reader is referred to the ex- 

 cellent review by Zeller.^^ 



When paraffin sections of animal tissues are incubated 

 with a "solution" of lecithin ( or cephalin ) in the presence of 

 Ca ions around pH 7, no reaction whatsoever is obsei'ved, 

 even on prolonged incubation (up to 12 hours ).^^ At this 

 pH, the Ca salts of fatty acids, if any were liberated, would 

 precipitate promptly (see the Tween technique, p. 203), 

 while Ca phosphate would not, unless the formation of phos- 

 phate ions were very rapid. At pH 9 a picture essentially iden- 

 tical with the pattern of distribution of alkaline phosphatase 

 is obtained.^^ It should be mentioned here that Dempsey 

 and Deane,^^ and Dempsey and Wislocki^^ did obtain posi- 

 tive reactions with lecithin around the neutral range but only 

 after greatly prolonged incubation (24-72 hours). The arti- 

 facts produced under such conditions have been discussed 

 (p. 176). 



The findings seem to indicate that the enzymes responsible 

 for the hydrolysis of bonds A and B cannot be demonstrated 

 histochemically. This is surprising in view of the fact that 

 such enzymes are known to occur in many animal tissues and 

 that they are quite resistant to heat. The enzyme active at 

 pH 9 and demonstrated histochemically acts either as leci- 

 thinase C or as lecithinase D. In the first case, the primary 

 precipitate would be the Ca salt of phosphorylcholine; in the 

 second case, Ca phosphatidate. Whether the primary pre- 

 cipitate is further hydrolyzed to Ca phosphate cannot be 

 decided on the basis of data available. 



The interesting point is that, just as in the case of the sim- 



57. Zeller, E. A.: Enzymes as essential components of bacterial and animal 

 toxins. In Sumner and Myrback's The enzymes (New York: Academic Press, 

 1951). 



58. Gomori, G.: Unpublished. 



59. Gomori, G.: Proc. Soc. Exper. Biol. & Med., 70:7, 1949. 



60. Dempsey, E. W., and Deane, H. W.: J. Cell. & Gomp. Physiol., 

 27:159, 1946. 



61. Dempsey, E. W., and Wislocki, G. B.: Am. J. Anat., 80:1, 1947. 



