486 



DIGESTION IN THE INTESTINES. [CH. XXXII. 



diffusible products. The fats are not chemically altered in the 

 stomach ; their proteid envelopes are, however, dissolved, and 

 the solid fats are melted. Starch is unaffected ; but cane sugar 

 is inverted. The im r ersion of cane sugar is largely due to the 

 hydrochloric acid of the juice, and is frequently assisted by 

 inverting ferments contained in the vegetable food swallowed. 



CHAPTER XXXII. 



DIGESTION IN THE INTESTINES. 



HERE we have to consider the action of pancreatic juice, of bile, 



and of the succus entericus. 



The Pancreas. 



This is a tubulo-racemose 

 gland closely resembling the 

 salivary glands in structure. 

 The principal differences are 

 that the alveoli or acini are 

 more tubular in character ; 

 the connective tissue be- 

 tween them is looser, and 

 in it are small groups of 

 epithelium-like cells, which 

 are supplied by a close net- 

 work of capillaries (fig. 400). 

 The secreting cells of 

 the pancreas are polyhedral. 

 When examined in the fresh 

 condition, or in preparations 

 preserved by osmic acid, 

 their protoplasm is seen to 



be filled in the inner two-thirds with small granules ; but 

 the outer third is left clear, and stains readily with reagents 



( fi g- 399)- 



During secretion the granules are discharged ; the clear zone 

 consequently becomes wider, and the granular zone narrower. 



These granules indicate the presence of a zymogen which is 



- 399- Section of the pancreas of a dog 

 during digestion, a, alveoli lined with 

 cells, the clear outer zone of which is well 

 stained with heematoxylin ; d, duct lined 

 with short cubical cells, x 350. (Klein 

 and Noble Smith.) 



