Action of Pancreatic Juice on Milk.— When pancreatic juice is mixed with milk at the body temperature the milk soon clots, but as the clotting stage is very brief, the curd being dis solved by the proteolytic action of the Trypsin, the milk-curdling function has been ascribed by some authorities to the Trypsin and not to a special pancreatic rennin.
The Bile in Its Digestive Bile is to be looked upon not as a digestive juice in the same sense as saliva, but as an excretion which incidentally assists the digestive action of the pancreatic juice. The reciprocal relations, both chemical and nervous, existing between the se cretion of gastric, pancreatic juice and bile have already been described.
As far as digestion is concerned, bile has five important functions. (1) It precipitates the acid-metaprotein and the proteoses resulting from gastric digestion of proteins, and the con version of a fluid or semi-fluid material into this solid condition allows more time for the action of pancreatic juice. (2) Bile salts act as a coenzyme or activator to each of the principal ferments of the pancreatic juice. In the presence of bile salts the power of the'pancreatic amylase is doubled, the proteolytic power of Trypsin is doubled and the action of the pancreatic lipase is augmented 20 times. (3) Bile promotes the absorption of the products of digestion. When bile is prevented from entering the intestine 60 per cent of the fat of a meal passes into the faces undigested, while normally the fat should almost have entirely disappeared from the faces. (4) Bile salts stimulate the peristaltic
movements on the intestines. (5) The re absorbed bile salts stimulate the liver to further secretion.
Function of the Intestinal tinal juice converts Trypsinogen into Trypsin by Enterokinase. It also contains two enzymes which convert the disaccarhides, cane-sugar and lactose into monosaccarhides. These fer ments are called invertase and lactase. The terminal stages of hydrolysis of proteins are affected by a ferment called Erepsin. Erepsin acts on proteoses and peptones, splitting them up into amino-acids. The secretin spoken of in the preceding as causing the secretion of pan creatic juice is not poured out into the lumen of the intestines but reaches the pancreas by way of the blood channels. It is not a ferment because it is not destroyed by boiling. The normal stimulus for the secretion of intestinal juice is undoubtedly this very secretin and pos sibly other hormones. It is not satisfactorily demonstrated that the intestinal secretion is influenced by a nervous factor. Herruneter has conceived of the digestive secretions as under control of two chemic factors — (1) stimula tors, and (2) arresters of secretion. The first are the hormones already described. The sec ond he designates as koliones from eoatov, to check or inhibit. Some of the end products of digestion act as koliones.