TEXT-BOOK OF PHYSIOLOGY. 



cord or membrane. The body is the active, contractile region, the 

 source of the movement ; the ter^ori is the inactive region, jhe^assive 

 transmitter of the movement to the bones. 



A skeletal muscle is a complex'organ -consisting of a framework of 

 connective tissue, supporting muscle-fibers, blood-vessels, nerves, and 

 lymphatics. The general body of the muscle is covered by a dense 

 layer of connective tissue, the epi-mysium, which blends with and 

 partly forms the tendon. Fro^M^^mBef surface of this covering, 

 septa of connective tissue pass inward, dividing and grouping the 



fibers into larger and smaller 

 bundles, termed fasciculi. The 

 fasciculi, in vested ^By a special 

 sheath, the peri-mysium, are 

 prismatic in sliape and on 

 cross-section present an ir- 

 regular outline. The muscle- 

 fibers composing the fasciculi 

 are separated one from an- 

 other and supported by a very 

 delicate connective tissue, the 

 endo-mYsium. The connec- 

 tive tissue thus surrounding 

 and penetrating the muscle 

 binds the fibers into a dis- 

 tinct organ and affords sup- 

 port to all remaining struc- 

 tures (Fig. 15). 



Histology of the Skeletal 

 Muscle-fiber. The muscle- 

 fibers for the most part are 

 arranged parallel one to an- 

 other and in a direction cor- 

 responding to the long axis of 

 the muscle. They vary in 

 length from 30 to 40 milli- 

 meters and in breadth from 



20 to 30 micromillimeters. There, ^re exceptional fibers, however, 

 which have a much greater length. *m^s the fibers have but a limited 

 length in the vast majority of muscles, each end, more or less pointed 

 or beveled, is united to adjoining fibers by cementN In this way a 

 muscle is increased in length. 



When examined with the microscope, the muscle- fiber is seen to be 

 cylindric or prismatic in shape and to consist of a thin transparent 

 membrane, the sarcolemma, in which is contained the true muscle 

 or sarcous substance. The sarcolemma is elastic and adapts itself 



FIG. 15. FROM A CROSS-SECTION OF THE 

 ADDUCTOR MUSCLE OF A RABBIT. P. 

 Peri-mysium, containing two blood-ves- 

 sels, at g; m, muscle-fibers; many are 

 shrunken and between them the endo- 

 mysium, p, can be seen; at x the sec- 

 tion of muscle-fiber has fallen out. 



x ^ 



