368 THE HUMAN BODY. 



bile, secreted since the* last meal; this passing down the 

 hepatic duct has been turned back up the cystic duct (Dc, 

 Fig. 115) on account of the closure of the common bile-duct. 

 The acid chyme, stimulating"' nerve-endings in the duodenal 

 mucous membrane, causes reflex contraction of the muscular 

 coat of the gall-bladder, and a relaxation of the orifice of the 

 common bile-duct; and so a gush of bile is poured out on the 

 chyme. From this time on, both liver and pancreas continue 

 secreting actively for some hours, and pour their products 

 into the intestine. The glands of Brunner and the crypts 

 of Lieberkiilm are also set at work, but concerning their 

 physiology we know very little. All of these secretions are 

 alkaline, and they suffice very soon to more than neutralize 

 the acidity of the gastric juice^and to convert the acid chyme 

 into alkaline chyle, which, after an ordinary meal, will con- 

 tain a great variety of things: mucus derived from the ali- 

 mentary canal; ptyalin from the saliva; pepsin from the 

 stomach; water, partly swallowed and partly derived from 

 the salivary and other secretions; the peculiar constituents of 

 the b^e and pancreatic juice and of the intestinal secretions; 

 some! digested proteids; unchanged starch; oils from the 

 fats eaten; peptones formed in the stomach but not yet ab- 

 sorbed; albumose; parapeptone; possibly salines and sugar 

 which have also escaped absorption in the stomach; and in- 

 digestible substances taken with the food. 



The Pancreatic Secretion is clear, watery, alkaline, and 

 much like saliva in appearance. The Germans call the pan- 

 creas the "abdominal salivary gland." In digestive prop- 

 erties, however, the pancreatic secretion is far more impor- 

 tant than the saliva, or even the gastric juice. Starch 

 it changes as the saliva does, but converts it into maltose 

 more quickly : and it acts also on proteids and fats. It 

 is by far the most important of all the digestive secretions. 

 All proteids not already converted into peptone or albumose 

 are acted upon by the pancreatic juice even more ener- 

 getically than in the stomach, being not only converted into 

 peptone, but in part further broken up, if the digestion (arti- 

 ficial) be prolonged, and converted into crystallizable nitrog- 

 enous bodies which, unlike peptone, retain no proteid-like 

 characters: the chief of these are leucin and tyrosin, the 

 former allied chemically to the fatty acids, the other to bodies 

 of the aromatic series. In normal digestion, however, it is 



