THE NUC LEO-PRO TEIDS. 67 
researches of Kossel, who obtained a carbohydrate from the nucleic acid of 
y< ast. 1 
Kossel and Neumann 2 have further shown that adenylic acid yields also 
a new acid called thymic acid, precipitable as a barium salt i'C,. IL X l'., ( > 12 Ba). 
The acid is readily soluble in cold water, and differs from nucleic acid in not 
being precipitated by mineral acids. 3 
Researches such as these show how complicated the subject is, and 
how much yet remains to be discovered, especially regarding the nuclein 
acids. The nuclein bases are comparatively simple, and the principal 
ones may be arranged in two groups: — 
Adenine has the formula C.-H-X.-: on heating it with sulphuric acid, 
XII is replaced by 0, and hypoxanthine is formed : — 
< ' II 4 X t .XH + H 2 = C,H,X,< ) + XII, 
(adenine) (water) (hypoxanthine) (ammonia) 
Both substances contain a radicle, C 5 H 4 X 4 , which Kossel terms adenyl : 
adenine is its imide, hypoxanthine its oxide. The following equation 
shows a similar relationship between guanine and xanthine:— 
C 6 H 4 N 4 O.NH + H 2 = C-,H 4 X 4 0, + XH 3 
(guanine) (water) (xanthine) (ammonia) 
On comparing the formulae of hypoxanthine and xanthine with uric 
acid (C 5 H 4 X 4 3 ), we see then close relationship. Leaving aside other 
possible ways in which uric acid is undoubtedly formed in the organism, 
we have here a way in which uric acid may arise by oxidation 
from the nuclein bases, and thus ultimately from the nuclei of cells. 4 
The name " alloxuric bases " for these substances was suggested by 
Kriiger and Wulff. 5 They are often spoken of as the " xanthine bases." 
The nucleo-proteids. — These are compounds of nuclein with pro- 
teids. The amount of proteid matter is large, and the substances in 
question give the reactions of proteids, and hi then solubilities approach 
very nearly to the globulins. On gastric digestion the nuclein they con- 
tain is left as an insoluble residue, but on pancreatic digestion a good 
deal of the nuclein is dissolved, and presumably, when this occurs in the 
body, is absorbed. 6 
Hammarsten divides the nucleo-proteids into two classes : the first, to 
which he restricts that name, yields true nuclein on gastric digestion : 
the other class he calls nucleo-albumins ; these yield pseudo-nuclein on 
gastric digestion, and include caseinogen and vitellin. In addition to 
these, there are the phospho-gluco-proteids, which have already been 
described (p. G4). 
Nucleo-proteids, using the term in the widest sense, are obtain- 
1 Kossel and Neumann, Bcr. d. deutsch. chem. Gesellsch., Berlin, Bd. xxvii. S. 2215. 
- Ztschr. f. physiol. Chem., Strassburg, Bd. xxii. S. 74. 
3 It was later obtained from spermatozoa nuclein (Kossel, ibid., p. 188). Milroy (ibid., 
1S96, Bd. xxii. S. 307) states that the precipitate formed on adding nucleic acid to a solu- 
tion of albumin resembles true nuclein in its characters ; whereas the precipitate produced 
by thymic acid is somewhat similar to para-nuclein or pseudo-nuclein. 
4 This subject has been specially taken up by Horbaczewski (Sitzungsb. d. k. Akad. d. 
Wissensch., Wien, Bd. c). who has pointed out the close relationship between uric acid 
formation and leucocytosis. Diet increases uric acid formation by leading to an increase 
of leucocytes, or possibly, as some recent investigators think, the increase is chiefly due 
to the nuclein in the food ("Weintrand, Chem. Ccntr.-Bl., Leipzig, 1895, Bd. ii. S. 54, 
234, 310). See also Umber, Ztschr. f. klin. Med., Berlin, 1896, Bd. xxix. S. 174 ; Camerer, 
Ztschr. J. Biol., Miinchen, 1896, Bd. xxxiii. S. 139. 
Ztschr. f. physiol. Chem., Strassburg, 1894, Bd. xx. S. 176. 
6 Popoff, Ztschr. f. physiol. Chem., Strassburg, Bd. xviii. S. 533 ; Gumlich, ibid., S. 508. 
