GASES. 385 



Still other nitrogenous extractives may be obtained from muscle- 

 tissue, but, with the exception of taurin, inosinic acid, and carnosin 

 they are scarcely known. For a description of taurin see page 170. 



Inosinic Acid. Inosinic acid is apparently a constant con- 

 stituent of muscle-tissue, but is most abundantly encountered in the 

 muscles of ducks, from which Creite was able to isolate as much as 

 0.26 per cent., calculated as barium salt. 



The substance has the composition C 10 H 13 N 4 PO 8 , and is com- 

 monly regarded as a nucleinic acid. On decomposition with boiling 

 water it is said to yield hypoxanthin, trioxy-valerianic acid, and 

 phosphoric acid. Whether or not a relationship exists between 

 inosinic acid and phospho-carnic acid is unknown. 



Carnosin. Carnosin is a basic substance which has been found 

 in beef extract, and which possibly also exists as such in the fresh 

 muscle-tissue. Its formula is given by Gulewitsch as C 9 H 14 N 4 O 3 . 

 In its general properties the substance resembles arginin. On de- 

 composition it yields histidin and alanin. It is identical with 

 Kutscher's ignotin. 



GASES. 



Both, when at rest as also during its activity, the muscle-tissue is 

 constantly taking up oxygen from the blood and the lymph. This 

 is stored in the cells proper, and is extensively utilized in the oxida- 

 tion-processes which are constantly going on, but which occur with 

 increased intensity when the muscle is at work. Carbon dioxide is 

 similarly given off, and it can be readily proved that the oxygen 

 which is utilized in its formation is in part at least stored within the 

 tissue. Carbon dioxide is thus still given off, even when a muscle 

 is removed from the body and worked in an atmosphere which is 

 free from oxygen. It has been noted, moreover, that the amount 

 which is then set free is the same as that which results when the 

 muscle is worked in the presence of an abundance of oxygen. Of 

 the form, however, in which the gas exists in the muscle we know 

 nothing, but it is manifestly not present in the free state, as no 

 oxygen at all, or very small amounts only, can be extracted by a 

 vacuum pump. With increasing activity larger amounts of oxygen 

 are taken up, while larger amounts of carbon dioxide are being 

 given off. This difference is well shown in the following table, 

 which is taken from Gautier. The figures have reference to 100 

 volumes of blood, calculated at C. and 1000 Hgmm. pressure : 



Carbon 

 Oxygen, dioxide. 



Arterial blood from muscle-tissue 15.25 26.71 



Venous blood from muscle-tissue while at rest . . 6.70 33.20 

 Venous blood from muscle-tissue while at work . . 2.97 36.38 



In addition to carbonic acid, small amounts of nitrogen can fur- 

 ther be obtained from muscle-tissue, which are manifestly absorbed 

 from the blood and apparently exist in a state of solution. As in 



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