206 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



by an extensive lymphatic network. The same is 

 true of the lymph nodules in Peyer's patches. 



Nerve Supply of the Alimentary Canal. The chief 

 nerve supply of the alimentary tract consists of sym- 

 pathetic neurons whose nerve cells form the centers 

 of two plexuses, (i) that of Auerbach, situated 

 between the two layers of the muscle coat, and (2) 

 that of Meissner in the submucosa. The latter con- 

 tains fewer ganglia and finer fibers. The numerous 

 small sympathetic ganglia of each plexus are united 

 by small bundles of non-medullated nerve fibers in 

 which a few medullated nerve fibers are present. 

 From these plexuses the nerve innervation extends 

 to the glands and epithelial cells of the mucosa, and 

 to the muscularis to end in small varicosities about 

 the smooth muscle cells. 



While the nerve innervation is not under will con- 

 trol it is capable of being stimulated by cerebro- 

 spinal nerves. Medullated nerve fibers from this 

 system have been traced to terminal end baskets 

 surrounding cell bodies of many of the sympathetic 

 neurons of these plexuses. 



