DIGESTION 195 



from the liver at the transverse fissure. At a distance of about 5 centimeters 

 it is joined by the cystic duct, the distal extremity of which expands into a 

 pear-shaped reservoir, the gall-bladder in which the bile is temporarily 

 stored. The duct formed by the union of the hepatic and cystic ducts, the 

 common bile-duct, passes downward and forward for a distance of about 

 7 centimeters, pierces the walls of the intestine and passes obliquely through 

 its coats for about a centimeter and opens into a small receptacle, the ampulla 

 of Vater. The ampulla in turn opens on a small papilla into the intestine. 

 The walls of the biliary passages are composed of a mucous membrane 

 internally, a fibrous and muscular coat externally. The termination of the 

 common bile-duct is provided with a distinct band of circularly disposed 

 muscle-fibers, which when in action completely close the orifice and prevent 

 the discharge of bile. It may therefore be regarded as a true sphincter 

 muscle, the structure and function of which were first pointed out by Oddi. 

 Small racemose glands are embedded in the mucous membrane of the main 

 ducts. 



Physical Properties. The bile obtained directly from the liver through 

 a cannula inserted into the hepatic duct is always thin and watery, while 

 that obtained from the gall-bladder is more or less viscid from admixture 

 with mucin, the degree of the viscidity depending on the length of time it 

 remains in this reservoir. The specific gravity of human bile varies within 

 normal limits from i.oio to 1.020. The reaction is invariably alkaline in 

 the human subject when first discharged from the liver, but may become 

 neutral in the gall-bladder. The alkalinity depends on the presence of 

 sodium carbonate and sodium phosphate. When fresh, it is inodorous; but 

 it readily undergoes putrefactive changes, and soon becomes offensive. Its 

 taste is decidedly bitter. When shaken with water, it becomes frothy a 

 condition which lasts for some time and which is due to the presence of mucin. 

 In ox bile the mucin is replaced by a nucleo-protein. 



The color of bile obtained from the hepatic duct is variable, usually a 

 shade between a greenish-yellow and a brownish-red. In different animals 

 the color varies. In the herbivorous animals it is usually green; in the car- 

 nivorous animals it is orange or brown. In man it is green or a golden 

 yellow. The colors are due to the presence of pigments. Microscopic 

 examination fails to show the presence of structural elements. 



Chemic Composition. The composition of human bile apparently 

 varies, even when obtained directly through a fistula as shown by the two 

 following analyses. 



COMPOSITION OF HUMAN BILE 



Jacobson Rosenbloom 



Water 977 .40 970 . 2 



Sodium glycocholate 9 -94 1 



Sodium taurocholate a trace / 



Cholesterol 0.54 2.6i l 



Free fat o.io 6.85 



Soaps. 1.36 2.60 



Lecithin o .04 6 . 42 



Mucin and pigments .- 2 .26 4 . 86 



Inofganic matter 8.36 9.2 



In this analysis the solid ingredients constitute 22.6 and 39.8 parts per 

 1000 respectively, of which two- thirds are organic and one- third inorganic. 

 The amount of solid varies according to the animal from which the bile 

 is obtained. 



1 Includes cholesterol esters. 



