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PSYCHOBIOLOGY 



The muscles of the human body are usually classified under three heads- 



1. Striated (striped) or 'voluntary'. 



2. Non-striated (non-striped), smooth, or 'non-voluntary'. 



3. Cardiac (heart-muscle), striped, but non-voluntary. 



Striated muscle tissue forms the skeletal muscles, that is, the muscles of 

 the body wall and of the limbs; and also the muscles of the eye and ear„ 



isiill 



Fig. 19. Parts of two striped muscle fibers of dog. Magnified 270 diameters- 

 (Ranvier, Histologic) The fibers have been broken without breaking the sarco- 

 lemma. «, nucleus; s, sarcolemma; p, fluid between sarcolemma and muscle-cell. 



the diaphragm, the tongue, pharynx, larynx, upper part of the esophagus,, 

 and in part of the rectum and genital organs. 



Striated muscles develop from certain of the non-mesenchymal cells 

 of the mesoderm. These cells, which are called myoblasts, divide by re- 



