ALKALINE PHOSPHATES OF CELL NUCLEI 53 



stance been calcium phosphate, the rate of appearance of the 

 artefact should have varied about a hundredfold with this varia- 

 tion in the calcium concentration. It is, therefore, clear that 

 the diffusing material is not calcium phosphate. 



The next test was to ascertain whether the diffusing substance 

 might be alkaline phosphatase itself or an activator for alkaline 

 phosphatase. In these experiments the underlying sections were 

 either kidney sections or guinea-pig liver sections in which the 

 phosphatase activity had been destroyed by heating, by dipping 

 in hot water, or by exposure to dilute acid. Superimposed upon 

 the inactivated section was a 50 /* section of guinea-pig kidney. 

 The top section was allowed to remain in contact with the 

 underlying section for 2 days in a sodium barbitone-calcium ni- 

 trate solution (corresponding to the incubation medium but 

 without substrate for phosphatase). After that period the 

 superimposed section was removed and the underlying section 

 incubated by itself. Plate V, Fig. B, shows the result obtained. 

 There is an intense reaction for phosphatase in what was 

 originally material lacking phosphatase. Since the active sec- 

 tion was removed before any incubation in the presence of sub- 

 strate for phosphatase was carried out, it follows that the dif- 

 fusing substance cannot be calcium phosphate, cobalt phosphate, 

 or cobalt sulfide. It must be either phosphatase itself or a 

 substance present in the active section which can activate phos- 

 phatase in an underlying section. 



So far it has not been possible to discover whether the diffus- 

 ing substance is phosphatase or activator. If a layer of col- 

 lodium or cellophane is inserted between the inactive section 

 and the active one, the amount of diffusion is reduced to zero. 

 But this experiment does not decisively distinguish between the 

 two possibilities. 



When diffusion occurs from an active section into a liver 

 section, the pattern of distribution of the diffused material is 

 considerably different from that of the intrinsic phosphatase of 

 the liver section. Plate V, Fig. C, shows the phosphatase which 

 is intrinsically present in a guinea-pig liver section. It is mainly 

 present in the cell nuclei. Figure B of Plate V, on the other 

 hand, shows that when diffusion occurs the nuclei are only one 

 of the sites which take up the phosphatase reaction. It thus 

 seems probable that, unless guinea-pig liver contains a consider- 



