TERMINATIONS OF THE NERVES 



463 



out the substance of most of the voluntary muscles are so-called neuro- 

 muscular spindles, made up of small bundles of fibres surrounded with 

 a rather thick covering of connective tissue. These structures are one- 

 eighth to one-third of an inch (3 to 8 millimeters) long and about T |^ 

 inch (0.2 millimeter) in diameter. A medullated nerve-fibre passes to each 

 spindle, loses its medullary sheath, subdivides and the non-medullated 

 fibres form a network surrounding the sarcolemma. It is not certain 

 that they then penetrate the sarcolemma and terminate in the muscular 

 substance, although this view has been advanced. These spindles are 

 abundant near the connections of the muscles with the tendons. They 

 do not exist in the muscles of the 

 eye and of the tongue. The 

 neuro-muscular spindles are re- 

 garded by some physiologists as 

 sensory and connected with the 

 so-called muscular sense. 



Termination of Nerves in the 

 Involuntary Muscular Tissue. 

 Nerve-fibres form a plexus in the 

 connective tissue surrounding 

 the involuntary muscles and 

 then send small fibres into the 

 sheets or layers of muscular- 

 fibre cells, which branch and 

 probably go finally to the nuclei 



Of these Structures. In many Fig- 101. Two motor end-plates from a muscle of a 



instances, the fine terminal 



nerve-fibres branch, go into the 



nuclei of the muscular fibres and afterward pass out to join with other 



fibres and form a plexus. 



Termination of Nerves in Glands. Having formed a more or less 

 branching plexus, non-medullated fibres pass directly into the glandular 

 cells and terminate in the nucleoli. Anatomists have also described and 

 figured multipolar cells, interspersed with the glandular cells, in which 

 some of the nerve-fibres terminate. These, however, are not found in 

 the parotid. These nerve-fibres are regarded as glandular nerves and 

 are distinct from the vasomotor nerves. 



Modes of Termination of Sensory Nerves. There undoubtedly are 

 several modes of termination of the sensory nerves in integument 

 and in mucous membranes, some of which have been quite accurately 

 described. In the first place, anatomists now recognize three varieties 

 of corpuscular terminations, differing in their structure, probably, accord- 



lizard, X 250 (Sobotta). 

 , entering nerve-fibres ; sch, end-plate. 



