BODY TISSUES AND FLUIDS 461 



Fine called attention to the fact that the creatin content of the muscle 

 of a given species of animals was very constant (obviously that of a given 

 animal) and suggested this as a possible basis of the constancy in the 

 daily elimination of creatinin first noted by Folin. Later they pointed out 

 that the creatinin content of muscle was greater than that of any other 

 tissue, and also that in autolysis experiments with muscle tissue 

 the creatin (and any added creatin) was converted to creatinin at 

 :i constant rate of about 2 per cent daily, which is just about the normal 

 ratio between the muscle creatin and urinary creatinin. They also found 

 that, when creatin was administered to man or animals, there was a slight 

 conversion to creatinin which corresponds well with the above figure. These 

 facts all go to support the view that creatinin is formed in the muscle 

 tissue from creatin, and at a very constant rate, although no explanation 

 of the physiological significance of this transformation can as yet be 

 offered. 



For the rabbit Myers and Fine(c) found a creatin content of 0.52 per 

 cent, for the white rat 0.4Y per cent, for the dog 0.37 per cent and for two 

 human cases 0.39 per cent. This figure for normal human muscle was 

 likewise confirmed by Denis (e) who has reported data for the muscle cre- 

 atin on nearly a hundred human cases. In a series of determinations made 

 on persons dying from various chronic diseases the creatin of the muscle 

 was found to be reduced absolutely and relatively in many cases, especially 

 those in an emaciated condition. These are the type of cases which ex- 

 crete creatin and show low creatinin coefficients. Denis likewise found 

 the percentage of muscle creatin in children to be lower thani that of 

 adults, which is in harmony with the observation that children excrete 

 creatin. 



Of the nitrogenous extractives carnosin stands next to creatin in point 

 of quantity. It is a dipeptid containing histidin and alanin. By its syn- 

 thesis Baumann and Ingvaldsen(fr) have shown carnosin to be (3-alanyl- 

 histidin. Figures given for its contents in muscle vary from 0.035 to 0.30 

 per cent. About 0.05 per cent has been reported for human muscle. 



The amount of purin base nitrogen found in the muscle of mammals 

 is generally given as about 0.05 per cent. This is partly combined and 

 partly free. From the observations of Davis and Benedict on a combined 

 uric acid compound present in beef blood, it is apparent that purins may 

 even be oxidized to uric acid before they are split off from the sugar with 

 which they are combined in the nucleic acid molecule. Of the different 

 purins hypoxanthin is generally stated to be present in the largest amount, 

 although both xanthin and guanin are also present. 



As was pointed out by Marshall and Davis urea is so diffusible that it 

 is very evenly distributed throughout the tissues of the body, and this 

 has been amply confirmed by the observations of Mosenthal, Clausen and 

 Hiller on human muscle tissue in cases with and without nitrogen retention. 



