ISOLATION AND COMPOSITION OF DEOXYPENTOSE NUCLEIC ACIDS 329 



on an almost industrial scale. When the sodium nucleate is prepared by 

 this procedure in less gigantic dimensions and with efficient washing of the 

 chloroform gels to overcome entrapment, the yields range, in our experi- 

 ence, from 1.4 to 1.9%. Schwander and Signer^"" record 1.8%, Kay et a^.,'"^ 

 2.6 to 2.8%. The latter method and the procedure described above under 

 Section III.2.c.'° (2.6% yield) appear to permit the greatest recovery; but 

 all the processes outlined in detail before are, on the whole, quite satisfac- 

 tory, at any rate for many mammalian organs and for fish sperm. Some 

 special cases will be mentioned below. Although the method outlined by 

 Schwander and Signer^"" consumes much more time than the others, it 

 should not be forgotten that one of their nucleate preparations has afforded 

 the best X-ray photographs."^ ''^ [See Jordan, Chapter 13.] 



/. Miscellaneous Procedures and Applications 



The isolation methods discussed above, which were developed principally 

 for calf thymus, may be applied not only to thymus tissue of other genera 

 (sheep, pig, man)'" but also to several other mammalian organs (e.g., 

 spleen,"* kidney,"* thyroid"') without essential changes. For the prepara- 

 tion of satisfactory specimens of deoxypentose nucleic acid from other 

 organs, in particular liver,"' "^ exhaustive preliminaiy washing of the 

 minced tissue, to remove pentose-containing material, will be necessary; 

 and such specimens may have to be subjected to special purification pro- 

 cedures after their isolation, in order to free them entirely of pentose nucleic 

 acid, as will be discussed below. Nucleated erythrocytes have also served 

 as a source,"* as has hen's egg white. "^"^ Occasional observations on the 

 isolation of nucleic acids from malignant tissue are likewise recorded in 

 the literature.'" "^''^-'^^ 



While fish spermatozoa""*'^^ and testes,"* "^'-^ and also sea urchin 



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