268 THE ORGANS 



muscularis mucosae and empty either into a crypt of Lieberkiihn or 

 on the surface between the vilK. Brunner's glands frequently occur 

 in the pylorus, and it is not uncommon for the pyloric glands to 

 extend downward somewhat into the duodenum. Meissner's plexus 

 of nerve fibres, mingled with groups of sympathetic ganglion cells, 

 lies in the sub-mucosa (see page 276). 



3. The muscular coat (Figs. 163 and 171) consists of two well- 

 defined layers of smooth muscle, an inner circular and an outer 

 longitudinal. Connective-tissue septa divide the muscle cells into 

 groups or bundles, while between the two layers of muscle is a con- 

 nective-tissue septum which varies greatly in thickness at different 

 places and contains a plexus of nerve fibres and sympathetic ganglion 

 cells known as the plexus of Auerbach (see page 276). 



4. The serous coat consists as in the stomach of loose connective 

 tissue covered by a single la}'er of mesothelium. 



IV. THE ENDGUT 



The Large Intestine 



The wall of the large intestine consists of the same four coats 

 which have been described as constituting the walls of the stomach 

 and small intestine, mucous, submucous, muscular, and serous. 



1 . The mucous membrane has a comparatively smooth surface, 

 there being neither pits as in the stomach nor villi as in the small 

 intestine (Fig. 172). The glands are of the simple tubular variety, 

 are considerably longer than those of the small intestine, are almost 

 straight, and extend through the entire thickness of the stroma. 

 Owing to the closeness with which the gland tubules are packed, the 

 amount of stroma is usually small. The surface cells (Fig. 172, a) 

 are very high and narrow, with small, deeply placed nuclei, and are 

 not usually intermingled with goblet cells. Passing from the surface 

 down into the glands, the cells become somewhat lower and goblet 

 cells become numerous (Fig. 173, a and d). Both superficial and 

 deep cells rest upon a basement membrane similar to that in the small 

 intestine. The stroma also, though less in amount, is similar in struc- 

 ture to the stroma of the small intestine. 



The MUSCULARIS MUCOSA (Fig. 173, c) consists of an inner circular 

 and an outer longitudinal layer of smooth muscle. 



2. The submucosa (Fig. 172, e) consists of loosely arranged con- 

 nective tissue. It contains large blood-vessels and the nerve plexus 



