THE MUSCULAR SYSTEM 



245 



FIG. 109. Diagram 

 of a section of a muscle, 



The "Muscle-organ." We must dis- 

 tinguish between the term " muscle " 

 as applied to the muscular tissue and 

 the term as applied to a working group 

 of muscular tissue, which is an organ. 

 In the muscle, or muscle-organ, is 

 found a definite grouping of muscle 

 fibers such as will enable a large num- 

 ber of them to act together in the pro- showing the perimysium 



duction of the same movement. An and the bundles of fiber 



examination of one of the striated 



muscles shows the individual fibers to lie parallel in small 



bundles, each bundle being surrounded by a thin layer of 



connective tissue. (See Practical Work.) These small 



bundles are bound into larger 

 ones by thicker sheaths and 

 these in turn may be bound 

 into bundles of still larger 

 size (Fig. 109). The sheaths 

 surrounding the fiber bun- 

 dles are connected with one 

 another and also with the 

 outer covering of the mus- 

 cle, known as 



The Perimysium. The 

 plan of the muscle-organ is 

 revealed through a study of 

 the perimysium. This is not 

 limited to the surface of the 

 FIG. no. A muscle-organ in muscle, as the name sug- 



position. The tendons connect at one but properly i nc l u des 



end with the bones and at the other c 



end with the fiber cells and perimysium. the sheaths that surround the 



(See text.) bundles of fibers. Further- 



.TENDONS 



ARTERY 



VEIN 



