THE NITROGENOUS EXTRACTIVES. 379 



The scyllit which is found in cartilaginous fish, where inosit is ab- 

 sent, is closely related to the latter and, like this, gives the reaction 

 of Gallois. 



THE NITROGENOUS EXTRACTIVES. 



The nitrogenous extractives of muscle-tissue comprise the com- 

 mon derivatives of the nuclear nucleins, viz., xanthin, hypoxanthin, 

 guanin, and carnin ; further, traces of taurin, glycocoll, urea, and 

 uric acid ; more abundantly kreatin and kreatinin, and finally a 

 basic substance which has been isolated from beef extract, and which 

 Gulewitsch has termed carnosin. 



Kreatin and Kreatinin. Kreatin is a constant constituent of 

 the muscle-tissue of the vertebrate animals, while in the invertebrates 

 it has not as yet been found. Its amount is often quite considera- 

 ble, and it has been calculated that in adult man as much as 90 

 grammes could be extracted from the muscles of the entire body. 

 Its anhydride, kreatinin, on the other hand, is usually found only 

 in traces, but may occur in larger amounts, and notably in certain 

 fishes. 



Of the origin of kreatin little is known, and it is noteworthy 

 that the substance has thus far not been obtained from the animal 

 tissues directly by artificial means. It has been found in the brain, 

 in the thyroid gland, in the blood, in transudates, in the amniotic 

 fluid, and is also a constant constituent of the urine. In the vege- 

 table world it does not occur. 



From the observation of St. Johnson that the urinary kreatinin 

 is not identical with the substance, which can be isolated from 

 muscle-tissue, it has been concluded that the former may not be 

 derived from the muscles at all, but may possibly be referable to the 

 kreatin, which is found in other organs of the body and notably in 

 the thyroid gland. Its identity with these kreatinins, however, has 

 not yet been established, nor is there reason to suppose that these 

 forms differ from, the common kreatinin of the muscles. However 

 this may be, the kreatins, viz., kreatinins, are essentially specific 

 decomposition-products of muscle-tissue, and are unquestionably 

 derived from the common muscle-albumins. This is suggested by 

 the observation that larger amounts of kreatin and kreatinin can be 

 isolated from muscles that have previously been worked, than from 

 muscles that have been at rest. I have shown, it is true, that the 

 nitrogenous components of the muscle-tissue enter into considera- 

 tion only in a secondary manner, as a source of muscular energy, 

 but this does not preclude the possibility, that during work the 

 metabolism of the muscle-albumins is increased. That such an 

 increase will of necessity become more apparent during starvation is, 

 of course, self-evident, and we find, as a matter of fact, that under 

 such conditions a corresponding increase in the formation of kreatin 

 occurs. 



