DIGESTION. 



277 



Bile, as such, is not pre-formed in the blood. As just observed, it is 

 formed by the hepatic cells, although some of the material may be brought 

 to them almost in the condition for immediate secretion. When it is, 

 however, prevented by an obstruction of some kind, from escaping into 

 the intestine (as by the passage of a gall-stone along the hepatic duct) it 

 is absorbed in great excess into the blood, and, circulating with it, gives 

 rise to the well-known phenomena of jaundice. This is explained by the 

 fact that the pressure of secretion in the ducts is normally very low, and 

 if it exceeds f inch of mercury (16 mm.) the secretion ceases to be poured 

 out, and if the opposing force be increased, the bile finds its way into 

 the blood, 



Quantity. Various estimates have been made of the quantity of bile 

 discharged into the intestines in twenty-four hours: the quantity doubtless ' 

 varying, like that of the gastric fluid, in proportion to the amount of 

 food taken. A fair average of several computations would give 20 to 

 40 oz. (600 900 cc.) as the quantity daily secreted by man. 



Uses. (1) As an excrementitious substance, the bile may serve 

 especially as a medium for the separation of excess of carbon and hydrogen 

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

 the peculiarities attending its secretion and disposal in the foetus. During 

 intra-uterine life, the lungs and the intestinal canal are almost inactive; 

 there is no respiration of open air or digestion of food; these are unneces- 

 sary, 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 thick bile, mixed with intestinal secretion; the meconium, or faeces of 

 the foetus, containing all the essential principles of bile. 



Composition of Meconium (Frerichs) : 



Biliary resin 



Common fat and cholesterin 

 Epithelium, mucus, pigment, and salts 



15.6 

 15.4 

 69.0 



100.0 



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

 the purification of blood by direct excretion, i.e., by separation from the 

 blood, and ejection from the body without further change. 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 



