1913] H. C. Biddle and Paul E. Howe 389 



on a moistiire- and fat-free basis. An alteratlon in the direction of 

 increased nitrogen content is more in harmony with the changes 

 that actually take place in the muscle. The relatively greater de- 

 crease in the volume of the cytoplasm than of the nucleus, and the 

 apparent relative increase in the connective tissue, are modifications 

 in the direction of a higher nitrogen content of the muscle. The 

 proteins which predominate in the connective tissue and in the nuclei 

 of muscle contain higher percentages of nitrogen than do the pro- 

 teins which make up the major portion of the cytoplasm of the 

 cells. 



In addition to changes in the chemical nature of fasting muscle, 

 certain physical modifications arise: normal muscle is firm to the 

 touch and, when hashed, may be readily handled without sticking to 

 the fingers ; fasting muscle, on the other hand, is soft to the touch 

 and, when hashed, adheres tenaciously to the fingers. 



While the lowered percentage of nitrogen in the fresh skeletal 

 muscle, as a result of fasting, may be due to diminutions in the 

 Contents of moisture and fat, the difference in the composition of 

 heart and skeletal muscle cannot be explained in this way. If the 

 nitrogen content of normal striated and heart muscle be calculated to 

 the moisture- and fat-free basis, there still remains a greater per- 

 centage of nitrogen in the striated muscle. That there are differ- 

 ences in the relative proportions of the soluble protein and the 

 stroma in heart, and in striated and smooth muscle, has been shown 

 by Saxl,^'* who finds that seven-eighthsof the skeletal muscle consists 

 of soluble proteins while but one-third of the heart muscle is of this 

 nature. 



A careful differential study of the proteins of fasting muscle 

 should throw some light upon the nature of the disintegrative 

 processes which take place in the tissues as a result of fasting. 

 Such a study is contemplated. 



" Saxl : Beiträge s. ehem. Physiol. u. PathoL, 1907, ix, p. i. 



