MUSCULAR TISSUE. 31 



MYOSIN. 



Digest the above meat residue with 100 c.c. of 15 per cent 

 NH 4 C1 solution for 24 hours in a covered beaker. Then filter 

 and use the filtrate for the following reactions: 



(a) Pour a little of the solution, drop by drop, into a 

 beaker filled with water. Compare this reaction with a simi- 

 lar one under Globulins. 



(6) Heat a few c.c. of the filtrate. Filter and test the fil- 

 trate for Ca. Is myosin a coagulable protein ? 



(c) Saturate 10 c.c. of the filtrate with MgS0 4 . Filter and 

 test the filtrate for protein. 



(d) Try Adamkiewicz, Biuret, and Xanthoproteic tests. 



NITROGENOUS EXTRACTIVES. 



These substances, together with the non-nitrogenous 

 extractives, form the chief constituents of a hot-water extract 

 of muscular tissue, such as is known commercially as Liebig's 

 Extract. The most important of the nitrogenous extract- 

 ives are creatine, xanthlne, hypoxanthine, guanine, uric 

 acid, and urea. The latter two are only present in traces. 

 The purine bases represent in all probability an intermediate 

 stage in the nuclear metabolism of the muscle-cell between 

 the nucleins on the one hand and uric acid or urea on the 

 other. 



/NH 2 



CREATINE, HN = C< /CH 3 



N \ // 



X CH 2 -C< 



X OH 



Extract 500 grms. chopped beef with 500 c.c. water for 

 half an hour over the water-bath at 50 C. Strain as dry as 

 possible through muslin and make a second extraction in the 



