GENERAL PHYSIOLOGY OF MUSCULAR TISSUE. 45 



homogeneous prismatic rod, termed sarcostyle, separated from neighboring 

 rods by a slight amount of sarcoplasm. 



Briicke has shown that when the muscle-fiber is examined under crossed 

 Nicol prisms the dim band appears bright and the bright band appears 

 dim against a dark background, indicating that the former is doubly refract- 

 ile, or anisotropic, the latter singly refractile, or isotropic. The fiber, there- 

 fore, appears to be composed of alternate discs of anisotropic and isotropic 

 substance. 



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 ^ to -$fa 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 em- 

 ployed also tend to alter its normal composition. 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 spontaneously, 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 or myogen 

 fibrin. This protein 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 preexisting sub- 

 stance, which is supposed to be myosinogen or myogen. Myosin is digested 

 by pepsin and trypsin. According to Halliburton, muscle plasma contains 

 the following protein bodies: Myosinogen, paramyosinogen, 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; 



