PHYSIOLOGY OF MUSCLE TISSUE. ^1 



Structure of Non-striated Muscle-fiber. As the name implies, 

 the involuntary fiber is non-striated, being apparently uniform and 

 homogeneous in appearance. When isolated, the fiber presents itself 

 in the form of an elongated fusiform cell, varying from T ^ to ^J^ of 

 an inch in length. In some animals the fiber exhibits a longitudinal 

 striation, as if it were composed of fibers. The cell is surrounded by 

 a thin, elastic membrane, and contains a distinct oval nucleus. The 

 fibers are usually arranged in bundles and lamellae, and held together 

 by a cement substance and connective tissue. This non-striated 

 muscle tissue is found in the muscularis mucosse of the alimentary 

 canal as well as in the muscular walls of the stomach and intestines, 

 in the posterior part of the trachea, in the bronchial tubes, in the 

 walls of the blood-vessels, and in many other situations. 



Chemic Composition of Muscle. The chemic composition of 

 muscle is imperfectly understood, owing to the fact that some of its 

 constituents undergo a spontaneous coagulation after death, and that 

 the chemic methods employed also tend to alter its normal composi- 

 tion. When fresh muscle is freed from fat and connective tissue, 

 frozen, rubbed up in a mortar, and expressed through linen, a slightly 

 yellow, syrupy, alkaline, or neutral fluid is obtained, known as 

 muscle plasma. This fluid at normal temperature coagulates spon-. 

 taneously, and resembles in many respects the coagulation of blood 

 plasma. The coagulum subsequently contracts and squeezes out 

 an acid muscle serum. The coagulated mass is termed myosin. 

 This proteid belongs to the class of globulins. Inasmuch as it is not 

 present in living muscle, and makes its appearance only in the as yet 

 living muscle plasma, it is probable that it is derived from some pre- 

 existing substance, which is supposed to be myosinogen. Myosin is 

 digested by pepsin and trypsin. According to Halliburton, muscle 

 plasma contains the following proteid bodies : Myosinogen, para- 

 myosinogen, albumin, myoalbumose; all of which differ in chemic 

 composition and respond to various chemic and physical reagents. 



Ferment bodies, such as pepsin and diastase ; non-nitrogenized 

 bodies, such as glycogen, lactic and sarcolactic acids, fatty bodies, and 

 inosite ; nitrogenized extractives e. g., urea, uric acid, kreatinin, as 

 well as inorganic salts, have been obtained from the muscle serum. 



Metabolism in Muscles. The chemic changes which underlie the 

 transformation of energy in living muscles are very active and 

 complex. 



