BILE 253 



C. LIPOLYTIC ENZYME, STEAPSIN 



In 1846 Cl. Bernard observed that in the dog fat suffered digestive changes 

 immediately after its entrance into the duodenum, whereas in the rabbit it 

 took place somewhat farther from the pylorus. The cause of this difference 

 he found to be the fact that in the dog the chief pancreatic duct opens into 

 the intestine in common with the ductus choledochus quite close to the pylorus, 

 while in the rabbit it opens some 30-35 cm. farther down. It follows that the 

 pancreatic secretion must have a determining influence upon the digestion 

 of fat. Further researches have shown that this effect consists in a cleavage of 

 the fat into glycerin and free fatty acid. We shall discuss the importance of 

 this cleavage more fully in our study of digestion in the intestine. 



5. BILE 



Human bile as it flows from the liver is a beautiful reddish-yellow or 

 yellowish-brown, or green, alkaline fluid, which on standing for some time 

 in contact with the air assumes a green or greenish-yellow color. It contains 

 a not insignificant amount of mucin, and the quantity of solids amounts to 

 1.5-4 per cent or more, of which 0.7-0.8 per cent is mineral. 



The daily output of bile, taken from men with biliary fistulas, has been 

 found to vary from 500 to 1,100 c.c. 



During the intervals of digestion the bile does not flow into the intes- 

 tine, but collects in the gall bladder, where by absorption of its water and 

 mixture with bladder mucus, it becomes more concentrated, so that its con- 

 tent in solids may rise sixteen or seventeen per cent higher. The specific 

 gravity of bile is 1.01-1.04. 



The most important constituents are mucin, the bile acids, and bile pig- 

 ments. The bile acids never occur free, but always as salts of the alkalies. 

 They are compounds of glycocoll and taurin (amino-ethyl-sulphonic acid: 

 NH 2 .C 2 H 4 .S0 2 OH) with cholic acid. Glycocholic acid (C 26 H 43 N0 6 ) and 

 taurocholic acid (C 26 H 45 NS0 7 ) occur in different biles in relatively different 

 quantities. In man the former is always present in greater quantity. Besides 



CCHOH 



the usual cholic acid, whose formula is C 20 H 31 I (CH 2 OH),, two other acids, 



[CHOH 



choleic acid (C 24 H 40 4 ),'and fellic acid (C 23 H 40 4 ) have been demonstrated 

 in human bile. Numerous derivatives can be obtained from the bile acids. 



The bile pigments are very numerous and they can be changed by various 

 means into still others. Under physiological conditions we have, properly 

 speaking, only two such pigments the reddish-yellow, bilirubin, and the 

 green, biliverdin. The former, which is easily crystallized in rhombic tablets, 

 is to be regarded as the mother-substance of biliverdin and all other bile 

 pigments. 



Bilirubin has the formula C 16 H 18 N 2 O 3 (Maly). It is transformed by oxida- 

 tion into biliverdin Ci H 18 N 2 O 4 , and vice versa the latter can pass by reduction 

 into bilirubin again. Biliprasin, according to Dastre and Floresco, is to be 

 regarded as an intermediate stage between the two. Bilirubin, acted upon by 



