GASES. 367 



It is obtained in indistinctly crystalline form. In hot water it is 

 readily soluble, while in cold water it dissolves with great difficulty, 

 and is insoluble in alcohol and ether. It is neutral in reaction, and 

 combines with acids and alkalies to form salts. These salts are not 

 decomposed by water. Its hydrochlorate, which results when adenin 

 is dissolved in warm hydrochloric acid, crystallizes out on cooling, 

 and combines with platinum chloride to form a double salt. Silver 

 nitrate precipitates it from its aqueous solutions as a silver salt, and 

 it is to be noted that this compound is insoluble both in ammonia 

 and nitric acid. Subacetate of lead precipitates adenin as a lead 

 salt ; this is soluble in boiling water. Acetate of copper produces 

 no precipitate. The substance gives none of the common reactions 

 of the xanthin-bases, and is best identified by the behavior of its 

 lead and silver salts. 



Still other nitrogenous extractives may be obtained from muscle- 

 tissue, but, with the exception of taurin and inosinic acid, they are 

 scarcely known. For a description of taurin see page 153. 



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 phosphor-carnic acid is as yet unknown. 



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, 



