370 VETERINARY PHYSIOLOGY 



When the individual is taking a liberal diet the secretion 

 of bile appears to be greater than when the diet is low. 



In fever there is a very marked fall in the secretion, the 

 fluid flowing from a fistula becoming colourless and almost 

 devoid of bile salts and pigments. 



Certain drugs markedly modify the formation of bile the 

 salts of the bile acids stimulating the liver to form more solids 

 and to secrete more water, the salicylates acting in much the 

 same way, and all drugs which cause haemolysis i.e. the 

 solution of the pigment of the erythrocytes producing an 

 increased formation of bile pigments. 



Influence, of Nerves upon the Flow of Bile (a) Expulsion of 

 Bile. There is good evidence that nerve fibres pass to the 

 muscles of the bile passages and that they may cause an 

 expulsion of bile by stimulating them to contract. 



(b) Secretion of Bile. There is no evidence that nerve fibres 

 act directly upon the secretion of bile. This appears to be 

 governed by the nature of the material brought to the liver by 

 the blood and by the activity of the liver cells. It is an 

 example of function regulated by chemical substances rather 

 than by a nerve mechanism. 



3. Mode of Formation of Bile. It has been seen that the bile 

 salts and pigments are actually formed in the liver cells, and 

 there is good evidence that the water of the bile is not a mere 

 transudation but is the product of the living activity of these 

 cells. The pressure under which bile is secreted may be 

 determined by fixing a canula in the bile duct or in a biliary 

 fistula and connecting it with a water manometer. In man 

 the pressure is as much as 20 to 30 mm. Hg, while the pressure 

 in the portal vein of the dog is only 7 to 16 mm. Hg. 



4. Nature and Functions of Bile. Bile is not a secretion of 

 direct importance in digestion. It has practically no action on 

 proteins or carbohydrates, and its action on fats is merely 

 that of a solvent, and possibly by its action on the surface 

 tension of the intestinal contents. Pavlov maintains that it 

 activates the lipase of the pancreatic juice, and others have 

 found that it increases the activity of trypsin and diastase. 

 It may thus be considered as an adjuvant to the action of 



