174 LOUIS BAUMAN 



COOII). Tliis compound is converted into crcatin when fed or injected 

 into animals (Czemicki; Jaffe, 1006; Dorner; Baunian and liines). 



Van Hoogenhuyze and Verploegh (a) (11)05) failed to observe an in- 

 crease in crcatinin excretion after the ingest ion uf proteins relatively rich 

 in arginin. Myers and Fine (1905) report that the concentration of 

 muscle crcatin does not appear to he markedly influenced by the feeding 

 of proteins having a high or low content of arginin. Jaffe (/) (1906) did 

 not observe an increase in creatinin excretion after the injection of arginin 

 into rabbits. Baiiman and Marker also failed to note an increase of 

 muscle creatin when arginin was circulated through dog muscle. 



Thompson (a) (1917) administered argiuin to ducks, dogs and rabbits 

 and observed an increase in the elimination of crcatin or creatinin and of 

 the creatin content of the muscle. Inouye observed that arginin was con- 

 verted into creatiu when perfused through the liver of cats. In growing 

 pigs the nature of the protein in the diet determines whether or not 

 creatin appears in the urine (McCollum and Steenbock). Denis (/) 

 (1917) has shown that the creatin excretion in hyperthyroidism may bo 

 much increased by the addition of protein to the diet. In children the 

 creatin of the urine varies with the amount of protein in the diet (Denis 

 and Kramer). Creatinuria in women follows the ingest ion of large 

 amounts of protein (Denis and Minot (a)). 



Riesser observed an increase in muscle creatin and in the creatinin 

 excretion of rabbits after the injection of cholin and betain. 



Harding and Young found that arginin was without effect on the 

 creatin excretion of growing dogs but that a variation in the cyst in con- 

 tent of the diet was followed by a similar variation in the creatin 

 elimination. 



Most recently Wishart observed an increase in muscle creatin follow- 

 ing the injection of guanidin salts into cats, dogs and frogs. The as- 

 sumption is that giianidin is detoxicated by conversion into creatin. 



In the foregoing experiments the factor of creatin destruction by the 

 tissues must not be overlooked. Creatin may be synthesized from a 

 precursor bnt subsequently destroyed, 



Creatin Metabolism 



Muscle. Before discussing this subject it may be well to remind the 

 reader that the experimental results obtained by different investigators are 

 often conflicting and therefore hard to reconcile? with one another. 



Considerable evidence seems to show that creatin is a product of muscle 

 metabolism. Its preponderance in muscle suggests that it results from 

 metabolic processes peculiar to this tissue (Pekelharing). Muscle creatin 

 increases with an increase in muscle tonus and conversely paralyzed muscle 



