22 LECTURE II. 



pentoses accordingly take part in the construction of animal tissue. The 

 only pentose which has been isolated from the organs and closely studied 

 is that from the pancreas-proteids, which C. Neuberg 1 has identified 

 as /-xylose with the following configuration: 



OH H OH 

 HC C C C CH 2 OH 

 H OHH 



It belongs, therefore, to the aldoses. 



Recently Wohlgemuth 2 has isolated the same pentose from liver-pro- 

 teid. 3 According to other investigations, it appears that the pentoses in the 

 animal organism are limited to the class of nucleoproteids, and in fact 

 that the carrier of the pentoses is not the albumin, but rather the other 

 component of the compound protein. This was shown, namely, by the 

 experiments of Ivar Bang/ who succeeded by warming pancreas-nucleo- 

 proteid with dilute caustic potash in decomposing it into albumin and into 

 a product free from albumin, the so-called guanylic acid. This latter con- 

 tains the Z-xylose. Guanylic acid is decomposed by boiling with mineral 

 acids into guanine, glycerol, and pentose; it may therefore be considered 

 as glycerophosphoric acid in which the hydroxyl groups are partly re- 

 placed by guanine and partly by pentose. As to whether the pentose is 

 similarly combined in the other nucleoproteids has not yet been established. 



The quantity of pentoses contained in the separate organs varies greatly 

 and depends directly upon the amount of nucleic substances present. 

 Grund 5 estimates the percentage of pentoses (calculated as xylose) present 

 in certain organs as follows: 



Pancreas 2 .48 



Liver .56 



Thymus 0.56 



Submaxillary Gland .53 



Thyroid Gland . 0.50 



Kidneys 0.49 



Spleen 0.46 



Brain 0.22 



Muscle . 0.11 



The values represent the 

 percentage of pentose (cal- 

 culated as xylose) in the 

 dry substance. 



As has already been mentioned, the first pentose was discovered in 

 urine and formed by metabolism in the human organism. The disease 



1 Ber. 36, 1467 (1902). 



3 Z. physiol. Chem. 37, 475 (1903). 



3 For further particulars and other literature, see Neuberg in Ergeb. Physiol. 

 (Asher and Spiro), 3, Abt. I, p. 373. 



4 Z. physiol. Chem. 31, 411 (1900-1901). 



6 Ibid. 36, 111 (1902). See also Bendix and Ebstein: Z. allg. Physiol. 2, Heft 

 1 (1902). 



