338 



STRUCTURE OF THE PANCREAS. 



wood ; and (2.) the inner layer (Bernard's granular layer) is strongly 

 granular, and stains but slightly with carmine. It undoubtedly con- 

 tributes to the secretion by giving off material, the granules being 

 dissolved, and this zone becoming smaller (Heidenhain). The spherical 



Fig. 140. 



Changes of the pancreatic cells in various stages of activity 1, During hunger ; 2, 

 in the first stage of digestion ; 3, in the second stage ; 4, during paralytic 

 secretion. 



nucleus lies between the two zones. [The lumen of the acini is very 

 small, and, according to Langerhans, spindle-shaped or branched cells 

 (centro-acinar cells) lie in it, and send their processes between the 

 secretory cells, thus acting as supporting cells for the elements of the 

 wall of the acini]. 



During secretion, there is a continuous change in the appearance of 

 the cell-substance ; the granules of the inner zone dissolve in the 

 secretion ; the homogeneous substance of the outer zone is reversed 

 and transformed into granules, which pass towards the inner zone 

 (Heidenhain, Kiihne, and Lea). 



Changes in the Cells during Digestion. During the first stage (6-10 



hours) the granular inner zone diminishes in size, the granules disappear, while 

 the striated outer zone increases in size (Fig. 140, 2). In the second stage (10-20 

 hours) the inner zone is greatly enlarged and granular, while the outer zone is 

 small (Fig. 140, 3). During hunger the outer zone again enlarges (Fig. 140, 1). 

 In a gland where paralytic secretion takes place, the gland is much diminished in 

 size, the cells are shrivelled (Fig. 140, 4) and greatly changed (Heidenhain). 

 According to Ogata, some cells actually disappear during secretion. When a 

 coloured injection is forced into the duct under a high pressure, fine intercellular 

 passages between the secreting cells are formed (Saviotti's canals), but they are 

 artificial products. 



Duct. The axially-placed excretory duct consists of an inner thick and an 

 outer loose wall of connective and elastic tissues, lined by a single layer of non- 

 striated columnar epithelium. Small mucous glands lie in the largest trunks. 

 The connective-tissue separates the gland into lobes and lobules. Non-medullated 

 nerves, with ganglia in their course, pass to the acini, but their mode of termina- 

 tion is unknown. The blood-vessels form a rich capillary plexus round some acini, 

 while round others there are very few. Kiihne and Lea found peculiar small cells 

 in groups between the alveoli, and supplied ' with convoluted capillaries like 

 glomeruli. Their significance is entirely unknown. [They are probably lym- 

 phatic in their nature.] The lymphatics resemble those of the salivary glands. 

 The pancreas contains water, proteids, ferments, fats, and salts. 



