STRUCTURE AND ARRANGEMENT OF THE MUSCLES. 



547 



with their tapering extremities in contact with one another. The fibers are not 

 held together by a viscid interstitial cement-substance, as was formerly supposed, 

 but they are universally connected by so->called cell-bridges. The conduction of 

 stimuli through unstriated muscles is at the same time thus explained. 



Where fibrils are visible in the fiber-cell (Fig. 189), they lie embedded in a 

 rather homogeneous, granular substance, the sarcoplasm. According to Engel- 

 mann, the disintegration of the substance of unstriated muscle into the separate 

 spindle-shaped elements is a postmortem change in the tissue. The transverse, 

 thickened areas occasionally observed are not due to transverse striation, but to 

 partial contraction or fold-formation (Fig. 184, 10). Unstriated muscle-fibers also 

 have tendinous insertions at times. The blood-capillaries pass in longitudinal 

 meshes between the fibers, as do also the numerous lymph-capillaries that surround 

 the cells. 



The motor nerves, according to J. Arnold, form a plexus of medullated and 

 non-medullated fibers, partially supplied with ganglion-cells, and situated in the con- 

 nective-tissue of the envelop surrounding the unstriated muscle-fibers the ground 

 plexus. From this arises a second non-medullated plexus, with nuclei at the nodal 

 points the intermediate plexus. This is situated either immediately upon the 

 musculature or in the connective tissue between the individual bundles. The 

 delicate fibrils (from 0.2 to 0.3 u) given off by this plexus unite to form still an- 



FIG. 190. Sensory Nerve in a Tendon. One fiber terminates in a Pacinian corpuscle (P), the other in a tendon- 

 spindle of Golgi (G). 



other network, the intermuscular plexus, and pass to each fiber, running along its 

 border and terminating in a pear-shaped thickening. According to Franken- 

 hauser the fibrils terminate in the nucleolus; according to Lustig, in the vicinity 

 of the nucleus; according to J. Arnold they traverse both fiber and nucleus and 

 re-enter the plexus. P. Schultz describes also sensory nerves, connected with 

 ganglion cells and provided with terminal nodules. 



In tendons the sensory nerves, after subdividing repeatedly, become non- 

 medullated fibers (Fig. 190, a), which at the junction of muscle and tendon twine 

 around or spread out over the bundles. This situation is covered with endothe- 

 lium. The non-medullated fibers terminate finally in a tuft of delicate ramifica- 

 tions, designated Golgi 's tendon-spindle. Terminations in the form of Pacinian 

 corpuscles (P) or end-bulbs are also found in the tendons. 



PHYSICAL AND CHEMICAL PROPERTIES OF MUSCULAR TISSUE. 



The consistency of muscular tissue is similar to that of living proto- 

 plasm; it is semi-solid, that is, not fluid to such a degree as to be diffluent, 

 nor is so solid that confluence of separated parts would not be possible. 

 The consistency, therefore, may be compared to that of a jelly at the 

 moment of liquefaction. 



