274 



MICROSCOPIC ANATOMY OF THE ORGANS. 



2. MUSCULAR SYSTEM. 



Large aggregations of striated muscle fibres form organs 

 which are called muscles. These taken collectively form the 

 muscular system. The muscle fibres are grouped together in 

 the muscles to form bundles (Fig. 200). Around each fibre 

 there is always a certain amount of connective tissue containing 

 blood capillaries, and bundles of these fibres are surrounded by 

 thicker stands of connective tissue known as the perimysium 

 internum. These primary bundles are grouped together by 



Peri my slum 

 internum 

 of priin 

 bundles 



"""^ III //SI II III 



Muscle fibres "^i.. ;l[23^\ intern** 



rx//f/ nf x'myle 



muscle fibres 



From a transverse section of the human stern o-cleido-mastoid muscle. An entire secondary 

 bundle, surrounded by the perimysium internum, is shown, x 45. 



connective tissue to form secondary bundles, which in large 

 muscles are enclosed still further to make up tertiary bundles. 

 The whole muscle is surrounded by a thick connective-tissue 

 capsule, the perimysium externum. This is in direct connection 

 with all the strands of connective tissue that make up the peri- 

 mysia interna. This can best be seen in a cross-section of a 

 muscle stained to bring the connective tissue into prominence 

 (e. g., with acid fuchsin and picric acid). We see that the 

 perimysium externum sends septa, into the muscle between the 



