11)12 MICROSCOPIC ANATOMY OF THE ORGANS. 



the fibres making up the large meshwork come together, there 

 are enlargements consisting of many multipolar ganglion cells, 

 from which new non-medullated fibres proceed. These cells are 

 to be observed in sections from any part of the alimentary canal, 

 as large cells with much protoplasm staining brightly in eosin, 

 and a large vesicular nucleus with well-marked nucleolus. 



From this plexus branches are sent into the submucosa, where 

 they form a second network, finer and more delicate than the 

 first, known as Meissner's plexus. In this the meshes arc 

 smaller, the fibre bundles more delicate, and the cell groups not 

 nearly so large. From this plexus fibres run throughout the 

 submucosa, and end also in the muscularis mucosaB and the 

 mucosa. They extend into the villi and end under the epi- 

 thelium in small swellings. 



F. PANCREAS. 



The pancreas is, like the salivary glands, a compound acino- 

 tubular gland divided by connective-tissue septa into lobules. 

 Two ducts, the duct of Wirsung (ductus pancreaticus) and the 

 duct of Santorini (ductus pancreaticus. accessorius), conduct the 

 external secretion to the intestine. These are lined with a 

 single layer of cylindrical epithelium, which is surrounded by 

 connective tissue containing small mucous glands. The inter- 

 lobular ducts pass directly into narrow intermediate ducts 

 (Fig. 147) lined with flat epithelial cells. The latter pass over 

 into the secreting end tubules of the gland. 



The glandular cells of the.se end tubules resemble those of 

 the serous tubules, as, for example, in the parotid gland. They 

 are rounded cells with highly refractile granules on the side 

 toward the lumen of the tubule. These are called zym<></< n 

 granules. The nucleus lies in the outer non-granular part of 

 the cell. The number of zymogen granules, as well as the 

 relation between the inner granular zone and the outer clear 

 part of the cell, varies according to the condition of the gland. 

 During digestion the granules gradually vanish and the cell 

 becomes clear. In fasting, the granules, on the contrary, 

 increase in number, and the granular inner zone takes up 



