184 FUNCTIONS OF NUTRITION. 



to its peristaltic movement. It is no doubt true that torpidity of the in- 

 testine is a usual accompaniment of clay-colored evacuations from the 

 absence of bile ; and on the other hand that bile, if applied to the mus- 

 cular coat of the intestine, will excite its contraction. But this cannot 

 be regarded as fully accounting for so abundant and peculiar a secretion. 



Furthermore, the bile has been thought to assist by its physical prop- 

 erties the absorption of oily matter by the intestine. It has been shown 

 by direct experiment to aid the passage of oily matter through organic 

 membranes or parchment paper ; that is, oily matter will pass through 

 these membranes more readily when they are moistened with bile than 

 when simply wetted with water ; and it is from these experiments that 

 the supposed action of bile has been inferred. But the villi of the in- 

 testine are not simply membranes moistened with water. They are 

 penetrated by alkaline and albuminous fluids, their blood-vessels con- 

 tain an abundance of liquid organic material, and the fatty emulsion 

 formed by the pancreatic juice is already adapted for absorption. 



Lastly, the bile has been credited with an action antagonistic to the 

 gastric juice, by which the gastric digestion is arrested, to be followed 

 by one of a different character in the small intestine. This is based 

 on the fact that the two secretions will precipitate with each other 

 when mingled in a test-tube. If one or two drops of dog's bile be 

 added to as many cubic centimetres of fresh gastric juice from the 

 same animal, a copious yellowish-white precipitate falls down, contain- 

 ing the whole of the coloring matter of the bile ; and when filtered, the 

 filtered fluid passes through colorless. A similar precipitation takes 

 place if, instead of fresh bile, a watery solution of the biliary salts be 

 added to gastric juice. The filtered fluid retains its acid reaction, 

 though it has lost its digestive power. 



But although the biliary matters precipitate by contact with fresh 

 gastric juice, they do not do so with gastric juice holding peptone in 

 solution. We have invariably found that if gastric juice be digested 

 for several hours at a moderate warmth with boiled white of egg, the 

 filtered fluid, which contains an abundance of peptone, will no longer 

 precipitate with either bile or a watery solution of the biliary salts, 

 even in large amount. The gastric juice and bile, therefore, do not 

 appear finally incompatible with each other in digestion, notwithstand- 

 ing their reaction when artificially mingled. 



The conclusion from these facts is on the whole a negative one ; and 

 it is the present belief of most physiologists that we cannot with con- 

 fidence assign to the bile any direct influence in digestion. This accords 

 essentially with the result of our own observations. 



Nevertheless, there is evidence that the bile is not simply an ex- 

 crementitious product, but that it takes part, in the alimentary canal, 

 in some process essential to life. This is shown by the fact that if it 

 be permanently diverted from the intestine by closure of the common 

 bile-duct, and evacuated by a fistula of the gall-bladder, the animals 

 gradually emaciate, and die with symptoms of disordered nutrition. 



