348 



TERMINATION OF MOTOR NERVES. 



modifications of these have been described but their fundamental structure appears 

 to be the same in all vertebrates. 



In muscles themselves little or nothing is known as to the endings of sensory 

 nerves, although that they possess such is shown by the pain which is felt when a 

 muscle is cut. Kerschner has described the " muscle spindles " (see p. 301) as 

 representing such sensory nerve-endings, but this view has not been generally 

 accepted. 



TERMINATION OP MOTOB NERVES. 



In the involuntary muscles such as those which constitute the muscular 

 layers of the hollow viscera, the nerves, which are for the most part non-medullated 

 with a small intermixture of white fibres, form complicated plexuses as they near 

 their termination. At the junctions of the fine nervous cords which compose the 

 plexuses groups of ganglion- cells are in many parts met with ; a well known example 



Fig. 409. NERVOUS PLEXUS OF AUERBACH FROM THE MUSCULAR COAT OF THE INTESTINE. (Cadiat.) 



of such a gangliated plexus being the plexus myentericus of Auerbach between the 

 longitudinal and circular layers of the muscular coat of the intestine (fig. 409). 

 From these gangliated plexuses branches are sent off, which penetrate between the 

 elements of the involuntary muscular tissue, coursing for the most part parallel with 

 the muscular fibres. The pale nerve-fibres bifurcate and give off branches at acute 

 angles at frequent intervals, and eventually become separated into fine filaments 

 which may represent ultimate fibrillas, but the branches which are given off only 

 rarely, according to Lowit, become united with those from adjoining nerve-fibres, so 

 that it can scarcely be said that an intramuscular plexus, and still less a network, 

 really exists. The fine longitudinally coursing fibrils come into close relation with 

 the involuntary muscle-cells, but do not appear to pass into the interior of the cells 

 and their nuclei. They are said to end by gradually tapering or varicose extremities, 

 but according to Elischer each nerve-fibril terminates by a slight bulbous expansion 

 opposite the nucleus of a contractile cell. 



In the cardiac muscular tissue the nerves form networks with very long 

 meshes. The nervous fibrils become closely applied to the muscular fibres, often 





