C. Voegtlin and C. P. Sherwin 149 
SUMMARY AND DISCUSSION. 
As will be seen from the data reported, cow’s milk contains 
small amounts of both guanine and adenine. 1 liter of*milk 
contains at least 5 mg. of adenine and about 10 mg. of guanine. 
These values may be considered as minimum values, as the 
method of isolation of these amino-purines is by no means quan- 
titative. It is interesting to compare these figures with those of 
Kriger and Salomon (1898-99) dealing with the adenine and 
guanine content of normal human urine. These authors found 
in 10,000 liters of urine 3.54 gm. of adenine, no guanine, 10.11 
em. of xanthine and 8.50 of hypoxanthine (accordingly, 1 liter 
of urine contains 0.85 mg. of adenine and no guanine). The 
question as to whether the purines found in milk are derived from 
the blood purines or whether they are formed from the breaking 
down of the nucleic acid in the mammary gland is still left open. 
BIBLIOGRAPHY. 
Schmidt-Miilheim, Arch. ges. Physiol., 1883, xxx, 379. 
Buridn, R., and Schur, H., Z. physiol. Chem., 1897, xxii, 60. 
Kriiger, M., and Salomon, G., Z. physiol. Chem., 1898, xxiv, 364; 1893-99, 
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