310 BACTERIAL POISONS. 



Neither adenine nor guanine occur in normal muscle 

 further than in mere traces, a fact which can only be 

 explained on the ground that the muscle tissue is poor in 

 nucleated cells, and hence in nuclein. Just as the muscle 

 cell has become morphologically differentiated from the 

 typical cell, it may be looked upon also as having under- 

 gone a concomitant chemical differentiation, inasmuch as we 

 no longer find the phosphoric acid, xanthine, and hypo- 

 xanthine in the same chemical combination as they occur in 

 the original cell. The phosphoric acid, instead of existing 

 as a part of an organic compound, is present in the muscle 

 tissue as a salt ; similarly the hypoxanthine and xanthine 

 occur in the free condition, extrattable by water, and no 

 longer in combination with other groups of atoms consti- 

 tuting a part of a more complex molecule nuclein. 



Guanine and creatine apparently mutually replace one 

 another. Thus, in the muscle, as just stated, guanine occurs 

 only in traces, whereas creatine is especially abundant. 

 This may find its explanation in the fact that both are sub- 

 stituted guanidines. Creatine is regarded by HOPPE- 

 SEYLER as an intermediate product in the formation of 

 urea, and a similar role, it will be remembered, belongs to 

 guanine. From STADTHAGEN'S experiments on dogs we 

 know that guaniue ingested, produces an increase in the 

 amount of uric acid and urea excreted, and the same is 

 also true of the nuclein derived from yeast. These results 

 have led him to the conclusion that in mammals uric acid 

 is a direct, or more or less altered cleavage product of pro- 

 teids, notwithstanding the fact that in birds it is the result 

 of synthesis in the liver. 



In the decomposition of nuclein-containing substances, 

 such as yeast, liver, spleen, etc., by dilute acids, neither 

 adenine nor guanine is found alone, but they are always 

 accompanied by hypoxanthine, and usually by a very small 

 quantity of xanthine. 



Guanine may be readily prepared from Peruvian guano 

 by boiling it repeatedly with milk of lime until the liquid 

 becomes colorless. The residue, consisting largely of uric 

 acid and guanine, is boiled with a solution of sodium car- 



