MUSCULAR MOVEMENT 



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give the name of striated muscle fiber to muscle masses 

 made up of such colls. Again, the fibrillaj may be entkely 

 free from such cross lines, and the muscle masses composed 

 of such cells are called non-striated muscle fiber. We have 

 already noted in man that the muscles are distinguished 

 by these differences. 



The simplest form of a muscle fibrilla is the unstriated 

 form foimd in the cell bodies of certain of the protozoans. 



Fig. 136 — Stentor, a one-celled protozoan in three stages of contraction ; 

 black lines are muscle fibers. 



the 



In the stentor (see Fig. 136) these fibrillse are arranged 

 parallel to one another so that by contraction they shorten 

 the whole cell. In other one-celled forms, such as the 

 vorticella, the fibrillse are united into a bundle which 

 extends the length of the stalk. The contraction of this 



