PHYSIOLOGY. 



dog fed on milk-sugar develops lactase in the pancreatic juice whilst 

 it normally contains little or no lactase. 



Maltase is also said to exist in the intestinal juice, splitting the 

 maltose into dextrose. 



The succus also contains another ferment known as enterokinase 

 a ferment of ferments. 



This ferment augments the activity of the pancreatic ferments, 

 especially the trypsin, by converting the trypsinogen of the pan- 

 creatic juice into trypsin. When dogs are fed only on starch and 

 fatty foods, then the pancreatic juice contains trypsinogen with the 

 object of protecting the amylopsin and steapsin. If the dogs were 

 fed on meat exclusively, then the pancreatic juice contained mainly 

 the ferment in the shape of trypsin. Unlike the stomach, mechani- 

 cal irritation of the intestine calls out increased secretion of the 

 succus entericus. But the intestine has a special stimulus, and Uiat 

 is the pancreatic juice. If a little pancreatic juice is inserted into 

 a loop of the intestine for half an hour, then a fluid will be secreted 

 containing much enterokinase. Every cannula introduced into an 

 intestine acts as a foreign body and excites a secretion of water, 

 with the object of washing it out of the intestine, and the amount 

 of enterokinase becomes steadily less and less. Hence a mechanical 

 stimulus calls out only water, and explains the severe diarrhoea of 

 acute enteritis, while the ferment enterokinase is called out by the 

 pancreatic juice. 



Secretin injected into the circulation causes a secretion of 

 intestinal juice. 



INNERVATION OF THE SMALL INTESTINE. 



If a piece of the small intestine between two ligatures has the 

 nerves going to it divided, then we have a paralytic secretion. A 

 similar state of affairs ensues after section of the nerves supplying 

 the submaxillary gland. In the intestinal segment with its nerves 

 divided will be found an abundant supply of intestinal juice, contain- 

 ing enterokinase and erepsin. This effect is probably due to sec- 

 tion of nerves which normally inhibit the secretion. The contigu- 

 ous intestinal segments with intact nerves are nearly empty. 



DIGESTION IN THE LARGE INTESTINE. 



Besides the changes wrought upon the foodstuffs in the mouth, 

 stomach, and small intestine by the various digestive secretions with 

 their powerful enzymes, there is still another more or less active 



