74 PHYSIOLOGY FOR DENTAL STUDENTS. 



bile duct and cause gall stones. The distention of the ducts 

 which these produce may cause great pain (biliary colic). The 

 formation of gall stones is encouraged by inflammatory processes 

 of the mucous membrane of the ducts. When bile fails to reach 

 the intestine, because of blocking the ducts, either by gall stones 

 or by inflammatory swelling of the mucous membrane, the di- 

 gestion, especially of fats, is much interfered with, and the faeces 

 become foul smelling and pale in color. 



The Composition and Properties of Pancreatic Juice. The 

 pancreatic juice contains three important enzymes: lipase (act- 

 on fats), amylopsin (acting on starch), and trypsinogen 

 ilflg on protein). Although the bile contains no enzymes, it 

 is, as we have seen, a most important accelerator of the activities 

 of the lipase and amylopsin of the pancreatic juice. Bile has no 

 action on trypsinogen, which is nevertheless without any action 

 until it has become changed into trypsin. This does not occur 

 until the pancreatic juice has reached the intestine, when the 

 activation is brought about by a ferment present in the intes- 

 tinal juice (secretion of Lieberkiihn's follicles), called enter o- 

 kinase. The intestinal juice contains this activator only when 

 it is required ; it is absent, for example, in the juice that is se- 

 creted as a result of mechanical stimulation of the intestinal mu- 

 cosa, but it immediately appears when some pancreatic secretion 

 is applied to the mucosa. Enterokinase is not the only substance 

 which can activate trypsinogen, for the addition of calcium salts, 

 the contact of the juice with leucocytes, as in granulation tissue, 

 and even mere standing of the juice, have a similar effect. If the 

 pancreatic juice in escaping from the duct should run over gran- 

 ulation tissue, as occurs when a fistula of the duct is made, it be- 

 comes activated and unless precautions are taken it will excoriate 

 the wound. Should it escape into the peritoneum, as when a 

 cyst bursts, it also becomes activated. By being secreted in an 

 inactive state, the proteolytic enzyme develops no digestive ac- 

 tion on the pancreatic ducts. 



It will be remembered that the amount of gastric juice secreted 

 varies with different foods, being relatively more abundant on a 

 diet of bread than on one of milk, or even meat (p. 63). Simi- 



