PHYSIOLOGICAL CHEMISTRY. 



After separation of the plasma what may be called the 

 stroma remains. This is mainly albuminous, but its exact 

 nature is not known. The sarcolemma portion of the muscle 

 fiber, which by weight makes up but a small part of the whole, 

 appears to belong to the albumoid group of proteins, resem- 

 bling elastin. It has been shown in an earlier chapter that 

 from ordinary dead muscle, as represented by lean meat, a con- 

 siderable amount of " myosin " may be separated by extract- 

 ing with a weak solution of ammonium chloride. What re- 

 mains does not agree fully with the stroma left on pressing 

 out the plasma of the fresh muscle, but contains approxi- 

 mately the same substances. By this method of separation 

 the insoluble stroma portion is much larger than the soluble 

 or " myosin " portion. The latter may amount to 7 or 8 per 

 cent of the weight of the muscle in the mean. 



Collagen. As given in the above table this refers to the 

 binding substance holding the muscle fibers together and in- 

 cludes the sarcolemma. It is insoluble in cold water, but 

 swells and disintegrates finally in boiling water. 



Fat. After removing all visible fat from the dissected 

 muscle, analyses still show a small amount remaining. This 

 must therefore be associated with the minute structure of the 

 fibrils. 



Flesh Bases. A number of very remarkable substances 

 are included here. They are sometimes described as the 

 nitrogenous extractives. The most abundant of these bodies 

 is creatine or methylguanidine acetic acid ; some of the purine 

 bases are also present. A brief description of these sub- 

 stances may be given. 



CREATINE, C 4 H 9 N 3 O 2 , may be represented structurally by 

 the formula 



/NH 2 



H-N=C< rR 

 \Tvr Chl 3 

 ^CH 2 COOH 



It is found in all muscles and is a product of metabolism. 

 Being readily soluble in warm water and in about 75 parts 



