214 FINE-STRUCTURE OF PROTOPLASM II 



the cytoplasm, in that part of their nucleotides do not contain d-ribose 

 but d-2-ribodesose. In this desoxypentose the OH-group at the 2nd 

 C-atom of ribose has been replaced by H. It is likely that this small 

 structural change causes the nucleic acids of the nucleus to be much 

 more sensitive to hydrolysis. For, according to Feulgen, after weak 

 acid hydrolysis the desoxyribose nucleic acids of the nucleus show 

 Schiff's aldehyde reaction with fuchsine in H.SOa. Obviously the 

 hydrolysis of the nucleic acids of the nucleus hberates the aldehyde 

 groups of ribodesose, whereas in the case of the nucleic acids of the 

 cytoplasm the aldehyde groups remain masked. Accordingly, this 

 specific staining has been introduced in cytological microchemistry as 

 Feulgen's nucleal reaction to prove the existence of desoxyribose 

 nucleic acids (Feulgen and Rossenbeck, 1924). 



It has been possible to analyze macrochemically a number of nucleic 

 acids showing a positive nucleal reaction. Thymonucleic acid from the 

 nuclei of the thymus gland consists of four nucleotides with the bases 

 adenine, thymine, guanine and cytosine. A molecule of this relatively 

 small size, however, will scarcely show colloid properties Hke the 

 nucleic acids in the nucleus. It must therefore be supposed that the 

 tetra-basic acid of Fig. 1 22 d represents only a part of the native nucleic 

 acids of high molecular weight. Guanyl nucleic acid from the pancreas 

 gland, the most complicated nucleic acid known at present, contains, 

 in addition to the tetra-basic thymonucleic acid, a nucleotide with 

 ribose as sugar and guanine as basic component. This shows that 

 mixed polymerization products of nucleotides with ribose and ribode- 

 sose groups can occur in the nucleic acids of the nucleus. For further 

 particulars we must refer to che literature concerned (e.g., Kiesel, 

 1930; Fischer, 1942). Specific differences of the nucleic acids in 

 different animals or in different organs of the same animal must be 

 looked for in the type of the basic side groups and their arrangement 

 along the chain. A microanalytical method for the determination of 

 pyrimidine and purine bases is possible by paper-chromatography 

 (ViscHER and Chargaff, 1948; Chargaff, 1950). 



Whereas formerly the nucleic acids were considered as tetra- 

 nucleotides, it was suggested in the first edition of this monograph 

 that they represent high polymer long chain molecules (Fig. i22d). 

 Signer, Caspersson and Hammarsten (1938) confirmed this by means 

 of the birefringence of flow of Na-thymonucleate and simultaneously 



