CREATINE AND CREATININE 71 



former substance can also be estimated indirectly by Folin's method. 

 A direct method for estimating creatine, due to Walpole [1911], is 

 based on the colour reaction with diacetyl (see appendix). 



Physiological. 

 Distribution. 



Creatine is a constituent of all vertebrate muscle. It was found 

 in the muscles of several animals by Liebig [1847], in the alligator 

 and in man by Schlossberger [1844, 1848], in a whale by Price [1851], 

 in a snake by Lyman [1908], in the cod and skate by Gregory [1848], 

 in various fishes and in Amphioxus by Krukenberg [i 88 1], and by 

 Suzuki and co-workers [1912]. It is not present in invertebrate 

 muscle [Krukenberg, 1881]. It is absent in the shrimp [Ackermann 

 and Kutscher, 1907, 1-4 ; Chapter III, betaine], absent in the cuttle- 

 fish [Henze, 1910; Chapter III, betaine], [Cabella, 1913], and absent 

 or present only in traces in Crustacea and Mollusca [Okuda, 1912]. 



Recently Myers and Fine [1913, I] have shown that for any 

 particular species the muscle creatine is remarkably constant. They 

 found 0*522 per cent, in the rabbit, 0^45 per cent, in the cat, 0-39 per 

 cent, in man, 0-37 per cent, in the dog. Other recent observations are 

 in close agreement with these determinations ; thus in rabbit's muscle 

 Riesser [1913] found 0*521 per cent, and Beker [1913] 0*523 per 

 cent. ; the latter found in dog's muscle 0*364 per cent. 



Creatine is most abundant in voluntary muscle (Cabella [1913], 

 Beker [1913]) ; there is less in cardiac and least in involuntary muscle. 

 According to Cabella the pectoral muscle of birds contains more than 

 that of the thighs ; in voluntary mammalian muscle and in the bul- 

 lock's heart the creatine nitrogen is 3-4 per cent, of the total ; in birds' 

 pectoral muscle 4-5 per cent. ; in cardiac muscle of birds and in the 

 muscle of the bullock's bladder I per cent. 



The following table [Beker, 1913] gives the amount of creatinine 

 in milligrams obtained from 100 grm. of various organs. The figures 

 must be multiplied by 1*16 to give their content as creatine. 



