THE NUCLEIC ACIDS 



phosphatases both with the sites of protein synthesis, particularly 

 of a fibrous nature (Jeener,^^ Bradfield^^), and also with concentra- 

 tions of nucleic acids suggests this possibility. Whether the trans- 

 peptidation reactions of Fruton^^ and Hanes, Hird and Isherwood^^ 

 are consonant with this mechanism is not yet clear. Chromosomes give 

 a strongly alkaline phosphatase reaction, and in the salivary glands of 

 Drosophila it has been shown that the enzyme is concentrated in the 

 Feulgen-positive bands (Danielli and Catgheside,^^ Krugelis^'). 

 In the intermitotic nuclei of chick cultures, the nucleoli and the 

 heterochromatic granules are also Gomori-positive, and the strength of 

 this reaction has been shown by Ghevremont and Firket^^ to be 

 correlated with the growth rate of the culture. 



Bracket and Jeener^^ have also shown that the intensity of the 

 Gomori reaction in several types of nuclei is paralleled both by their 

 frequency of mitosis and by their DNA turnover rates as measured 

 isotopically (Hevesy and Ottesen,^"" ^°^ Hammarsten and Hevesy^''^). 

 Thus fowl erythrocytes are Gomori-negative, they have a negligible 

 DNA turnover-rate, and do not undergo cell division, whilst on the 

 other hand in the cells of the intestinal crypts the opposite is true in 

 each instance, although the function of the alkaline phosphatase else- 

 where within the mucosal cells, and possibly in the nucleus as well is 

 related to the transport of metabolites. Moreover, in nuclei from the 

 cerebral cortex where the mitotic index is nil, Richter and Hultin^*^^ 

 report that both acid and alkaline phosphatases are there present in 

 higher concentrations than in the cytoplasm. 



As one surveys the general state of this subject at the moment it must 

 be admitted that the extent of our knowledge about what Jones^^* 

 termed the 'physiological conduct' of the nucleic acids within the cell 

 is still restricted to the barest outlines. In recent years, there has been a 

 tendency to explain every cellular change in terms of nucleic acids, 

 much as the Peripateticks once used to interpret all natural phenomena 

 in terms of the four elements. However, as Willey^"^ so lucidly ex- 

 pounds, the real purpose of all explanations is to satisfy mental needs. 

 In science such satisfaction can come finally from factual knowledge 

 alone. 



REFERENCES 



* Mann, G., Physiological Histology, Oxford, 1902 



* Baker, J. R,, J. Quekett micro. Soc, 4 (1943), 256 

 ' Greenstein, J. P., Sci. Mon., 57 (1943), 523 



* McDonald, M., J. Gen. Physiol, 32 (1948), 39 



" MiESCHER, F., Hoppe-Seyl. med-chem. Untersuch., 4 (1871), 441 



* Zacharias, E., Bot. Z^itiing Jahrg., 39 (1881), 169 



' Flemming, W., Z^llsubstanz, Kern, und ^elltheilung, Leipzig, 1882 ^ -.v,^ 



* Waldeyer, W., Arch. mikr. Anat., 32 (1888), i y'vSo^ ^ A /\ 



» Ehrlich, p., Z' f^lin. Med., i (1880), 553 /c^ ^- /\ 



LIBRARY = 



' MASS. /c:v 



