394 HANDBOOK OF PHYSIOLOGY. 



plained by its so aiding fat digestion that the fats are absorbed before 

 they can decompose. 



(d) The bile has also been considered to act as a natural purgative. 

 by promoting an increased secretion of the intestinal glands, and by 

 stimulating the intestines to the propulsion of their contents. This view 

 receives support from the constipation which ordinarily exists in jaun- 

 dice, from the diarrhoea which accompanies excessive secretion of bile, 

 and from the purgative properties of ox-gall. 



(e) The bile appears to have the power of precipitating the gastric 

 proteases and peptones, together with the pepsin, which is mixed up with 

 them, as soon as the contents of the stomach meet it in the duodenum. 

 It thus stops the action of the pepsin. The purpose of this operation is 

 probably both to delay any change in the proteoses until the pancreatic 

 juice can act upon them, and also to prevent the pepsin from exercising 

 its solvent action on the ferments of the pancreatic juice. In some way 

 its presence seems also to aid the action of trypsin. 



(/) As an excrementitious substance, the bile may serve especially as 

 a medium for the separation of certain highly carbonaceous substances 

 from the blood; and its adaptation to this purpose is well illustrated bj 

 the peculiarities attending its secretion and disposal in the foetus. Dur- 

 ing intra-uterine life, the lungs and the intestinal canal are almost in- 

 active; there is no respiration of open air or digestion of food; these 

 are unnecessary, on account of the supply of well-elaborated nutriment 

 received by the vessels of the foetus at the placenta. The liver, during 

 the same time, is proportionately larger than it is after birth, and the 

 secretion of bile is active, although there is no food in the intestinal 

 canal upon which it can exercise any digestive property. At birth, 

 the intestinal canal is full of concentrated bile, mixed with intestinal 

 secretion, and this constitutes the meconium, or faeces of the foetus. 

 In the foetus, therefore, the main purpose of the secretion of bile must 

 be directly excretive. Probably all the bile secreted in foetal life is 

 incorporated in the meconium, and with it discharged, and thus the 

 liver may be said to discharge a function in some sense vicarious of 

 that of the lungs. For, in the foetus, nearly all the blood coming from 

 the placenta passes through the liver, previous to its distribution to 

 the several organs of the body; and the abstraction of certain sub- 

 stances will purify it, as in extra-uterine life it is purified by the separa- 

 tion of carbon dioxide and water at the lungs. 



Mode of Secretion and Discharge. The secretion of bile is contin- 

 ually going on, but is retarded during fasting, and accelerated on taking 

 food. This has been shown by tying the common bile-duct of a dog, 

 and establishing a fistulous opening between the skin and gall-bladder, 

 whereby all the bile secreted was discharged at the surface. It was 

 noticed that when the animal was fasting, sometimes not a drop of bile 



