THE BILE: MECOXIUM. 327 



gall-bladder, and enters the duodenum on the introduction 

 of food into the small intestine : being pressed on by the 

 contraction of the coats of the gall-bladder, and probably 

 of the common bile-duct also ; for both these organs contain 

 organic muscular fibre -cells. Their contraction is excited 

 by the stimulus of the food in the duodenum acting so as to 

 produce a reflex movement, the force of which is sufficient 

 to open the orifice of the common bile-duct. 



Various estimates have been made of the quantity of bile 

 discharged in 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 thirty to forty ounces 

 as the quantity daily secreted by man. 



The purposes served by the secretion of bile may be con- 

 sidered to be of two principal kinds, viz., excrementitious 

 and digestive. 



As an excrementitious substance, the bile serves especi- 

 ally as a medium for the separation of excess of carbon and 

 hydrogen from the blood ; and its adaptation to this pur- 

 pose 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 unnecessary, because of the supply of well-elabo- 

 rated nutriment received by the vessels of the foetus at the 

 placenta. The liver, during the same time, is proportionally 

 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; for the meconium, or faeces of the foetus, are 

 shown by the analyses of Simon and of Frerichs to contain 

 all the essential principles of bile. 



