THE ALIMENTARY CANAL AND ITS APPENDAGES 451 



derived from the vagi. In the lower part of the thorax these nerves 

 consist mainly of non-medullated fibers, and lie on the sides of 

 the gullet, across which they interchange fibers by means of 

 several branches. On entering the abdomen the left vagus passes 

 to the ventral side of the stomach, in which it ends : the right sup- 

 plies the dorsal side of the stomach, but a considerable portion of 

 it passes on to enter the solar plexus, which lies behind the stomach 

 and contains several large ganglia. The thoracico-lumbar auto- 

 nomic fibers pass to the stomach as branches from the great splanch- 

 nic nerves, which serve as the chief paths of distribution for these 

 fibers in the abdomen. 



Histology of the Gastric Mucous Membrane. Examination of 

 the inner surface of the stomach with a hand lens shows it to be 

 covered, except in the fundic region, with minute 

 shallow pits. Into these open the mouths of 

 minute tubes, the gastric glands, which are closely 

 packed side by side in the mucous membrane ; 

 something like the cells of a honeycomb, except 

 that each is open at one end. Between them lie 

 a small amount of connective tissue, a close 

 network of lymph-channels, and capillary blood- 

 vessels. The whole surface of the mucous mem- 

 brane is lined by a single layer of columnar 

 mucus-making epithelium cells (m, Fig. 129). 

 These dip down and line the necks of the 

 tubular glands. The deeper portions of the 

 glands are lined by a layer of shorter and some- 

 what cuboidal cells, the central or chief cells. In 

 specimens taken from a healthy animal killed 

 during digestion these cells are large and do 

 not stain deeply with carmine. Similar speci- 

 mens taken from an animal an hour or two the gland; m, mu- 



, , , ,, -, * ,1 cous cells lining the 



after a good meal has been swallowed show the mo uth of the gland 

 chief cells shrunken and staining more deeply. f* er surface g of the 

 They thus store up during rest a material which u c <gus ce sp ^vai 

 they get rid of when the gastric juice is being cells, 

 secreted. 



In the pyloric end of the stomach only the chief cells line the 

 glands, but elsewhere there is found outside of them, in most 



-P 



FIG. 129. Dia- 

 of 

 D, 



