CREATININE. 659 



into each other, it has been considered for a long time that the urinary 

 creatinine is formed from the creatine of the muscles and other organs. 

 Unfortunately the authorities disagree on this question. FOLIN in his 

 investigations found that about 80 per cent of the creatinine intro- 

 duced was again eliminated, while the creatine taken did not appear in 

 the urine as creatinine, but was partly retained by the body and in 

 part eliminated as such. An intravital transformation of creatine into 

 creatinine is disputed by v. KLERCKER, MELLANBY and LEFMANN/ while 

 it is accepted by GOTTLIEB, STANGASSINGER, S. WEBER, v. HOOGEN- 

 HUYZE and VERPLOEGH and ROTHMANN, partly based upon autolytic 

 experiments (see Chapter XI). According to v. HOOGENHUYZE and 

 VERPLOEGH 2 a part of the creatine formed in the body is oxidized and a 

 part changed into creatinine. 



The proteins, or rather the guanidine groups therein, are considered 

 as the piobable mother substance of these two bodies. JAFFE has 

 indeed shown, which has been substantiated later by DORNER, S that in 

 rabbits glycocyamine (guanidine acetic acid) is in part changed into 

 creatine with the annexation of methyl. Guanidine occurs in the pro- 

 teins as arginine, but the observations of OTORi 4 show that it is not 

 improbable that the proteins also contain other guanidine groups. JAFFE 

 considers it improbable that the arginine is the mother substance of the 

 creatine, but rather another guanidine group. Under the circumstances 

 the proteins can be considered as the mother substance of the creatine 

 and creatinine, and in a previous chapter (XI) the experiments of SEEMAN 5 

 showed the abundant formation of creatine from protein by autolysis. 



If then the creatinine (creatine) originates from the protein, it is 

 evident that we must differentiate between food protein and body 

 protein. The quantity of creatinine is, inasmuch as it is increased by 

 meat diet, dependent upon the food; but otherwise, as found by FOLIN 

 and in chief substantiated by others, 6 is rather independent of the 

 food. Its elimination does not run parallel with the urea and the total 

 nitrogen, and consequently is not in general greater with food rich 

 in protein than with food poor therein. On the contrary, its extent, 

 as shown by other conditions, is dependent upon the intensity of the 

 metabolism in the cells, and the creatinine, according to FOLIN, is a 

 product of the endogenous protein metabolism. 



1 Folin, Hammarsten's Festschrift, 1906; v. Klercker, Bioch. Zeitschr., 3; Mellanby, 

 Journ. of Physiol., 36; Lefmann, Zeitschr. f. physiol. Chem., 57. 



2 See footnote 1, page 547, and v. Hoogenhuyze and Verploegh, Zeitschr. f. physiol. 

 Chem., 59. 



3 Jaffe, Zeitschr. f. physiol. Chem., 48; Dorner, ibid., 52. 



4 Zeitschr. f. physiol. Chem., 42, 43. 

 5 1. c., footnote 1, page 547. 



6 Besides the works cited above see also Closson, Amer. Journ. of Physiol., 16. 



