NEKVE ENDINGS IN MUSCLE AND TENDON 139 



FIG. 138. NERVE ENDINGS IN CARDIAC MUSCLE, 

 FROM THE HEART OF A CAT. 



a, muscle cells ; 6, nerve fibre. Methylen blue. 

 Highly magnified. (After Huber and De Witt.) 



B. Cardiac and Smooth Muscle 



The nerves of the heart are distributed to the cardiac ganglia, 

 whence non-medullated fibres pass to all portions of the organ 

 and form a very rich plexus 

 in the intermuscular con- 

 nective tissue. Fine ter- 

 minal fibrils are distributed 

 from this plexus to the * 

 muscle fibres, upon whose 

 surface they end in vari- 

 cose swellings and end 

 knobs. While most of 

 these fibrils are probably 



motor in function, others which, end in the intermuscular con- 

 nective tissue are more probably centripetal. 



In smooth muscle plexuses of sympathetic nerve fibres occur in 

 the intervals between the bundles of muscle fibres. Secondary 



plexuses of naked 

 fibrils are found 

 among the mus- 

 cle cells, and from 

 this plexus fine 

 lateral fibrils are 

 distributed to the 

 muscle cells, upon whose surface they end in small terminal gran- 

 ules or end knobs. Many of the nerve fibres in smooth muscle are 

 undoubtedly of sensory function. 



FIG. 139. NERVE ENDINGS IN SMOOTH MUSCLE, FROM THE 



INTESTINE OF A CAT. 



o, muscle cell ; 6, nerve fibre. Methylen blue. Highly mag- 

 nified. (After Huber and De Witt.) 



The nerve endings and the distribution of the peripheral nerve 

 fibres in the various organs of the body are more fully described 

 in the several chapters devoted to those organs. 



