BILE 137 



taurocholate, exert a profound influence over the digestion 

 of fat by the pancreatic Upase. When the bile-duct is 

 occluded nearly all the fat fails to be absorbed and appears 

 in the faeces. Bile-salts possess the peculiar property of 

 lowering the surface tension between fat and water. They 

 therefore break up the fat into an emulsion, thus enormously 

 increasing the surface upon which the lipase can work. 

 Moreover, they dissolve the soaps which are formed by 

 the hpase, and in so doing prevent the premature cessation 

 of hpolysis which would otherwise occur owing to the 

 formation of an insoluble coat of soap around each particle 

 of fat. Further, there is reason to beheve that bile has the 

 direct effect of stimulating the pancreatic lipase. 



The other constituents of the bile — bile-pigment, cho- 

 lesterol and lecithin — -are excretions, and play no part in 

 digestion. The bile-pigments are bilirubin and biliverdin. 

 They are partly excreted in the faeces as stercobilin, partly 

 reabsorbed and excreted by the kidney as urobihn. Cho- 

 lesterol and lecithin are products of metabohsm of all tissues. 

 In dissolving them the bile -salts perform yet another 

 function. 



The bile-salts are largely reabsorbed in the lower part 

 of the small intestine and are returned to the hver. 



The Antiseptic Action of pile 



Bile being a most perfect medium for growing intestinal 

 bacteria, it is obviously the very reverse of an antiseptic, 

 yet its absence from the intestine, as when the bile-ducts 

 are obstructed, leads to increased bacterial activity. While 

 it does not directly prevent the growth of bacteria, it 

 reduces the quantity of protein pabulum on which they 

 feed. This is due to its action in assisting in the saponifi- 

 cation of fats, for the meat-fibres which are commonly 

 enveloped in fat are thereby exposed to the action of the 

 proteolytic enzymes. Further, bile by its presence increases 

 the fluidity of the intestinal contents, and thus favours 

 drainage. 



