120 MUSCLE TISSUE 



the skeleton and the external muscles of the eye-ball, 

 in the tongue, the pharynx, upper part of the esophagus, 

 anus, diaphragm, larynx, and external ear. 



Involuntary Non-striated, Smooth or Visceral Muscle. 

 It is not under the control of the will. The individual 

 fibers are short, narrow, and spindle-shaped. Each 

 fiber is surrounded by a sheath, but it is not a sarco- 

 lemma. The fibers show longitudinal striation at the 

 periphery due to the presence of fibrillse, but no 

 transverse striation. There is only one nucleus, which 

 is narrow, elongated, and centrally located. 



The fibers form bundles, but instead of being formed 

 into masses like the voluntary striated variety, they 

 are arranged into layers which extend circularly, 

 obliquely, and longitudinally in the construction of the 

 hollow organs of the body. 



Bloodvessels are arranged as in the former variety. 



The nerves are mostly derived from the sympathetic 

 system. 



Non-striated muscles are found in the walls of the 

 alimentary tract, extending from the middle third 

 of the esophagus to the anus, in the ducts of glands, 

 trachea, and bronchial tubes, the eye"-ball, the internal 

 genito-urinary apparatus, walls of bloodvessels (except 

 the heart) and lymphatic system, and the capsules of 

 some organs. 



Involuntary Striated or Cardiac Muscle. It is found 

 in the muscle of the heart. The fibers are short 

 cylinders, showing striations, but no sarcolemma. A 

 delicate sheath surrounds the fibers. The nucleus is 

 large, oval, and placed in the centre of a zone of un- 

 differentiated protoplasm, filled with pigment granules. 

 There are seen longitudinal and transverse striations 

 in this variety, the latter being fainter. The fibers of 

 this variety branch and join with the branches of other 

 muscle cells. 



The bloodvessels are derived from the coronary 



