110 PHYSIOLOGICAL CHEMISTRY. 



fistula in man, the glycocholate was shown to be a constant ingredient, 

 while the taurocholate was either absent or variable in quantity. We 

 have also found human bile to contain the glycocholate without the 

 taurocholate. 



The biliary salts are formed in the tissue of the liver, and are 

 thence discharged with the bile. They are derived, in the opinion of 

 most physiologists, from a transformation of albuminous matters, as 

 indicated by the nitrogen and sulphur which they contain. According 

 to the observations of Ranke on a patient with biliary fistula, the aver- 

 age quantity of the organic acids of the bile thus -produced, in a man 

 weighing 65 kilogrammes, would be a little over 15 grammes per day. 

 Although a small amount has been found by Hoppe-Seyler in the feces, 

 this appears to be much less than the total quantity produced in the 

 liver for a corresponding time. Similar observations on animals have 

 also shown that the main part of the biliary salts are not discharged 

 with the feces, but are changed in the intestine, and, probably, reab- 

 sorbed under another form by the blood. 



Pettenkofer 's Test for the Biliary Salts. The biliary salts, when 

 in considerable quantity, may be recognized by their solubility in 

 water and in absolute alcohol, their insolubility in ether, their form 

 of crystallization, and their reaction with the salts of lead. When 

 present in small proportion they are detected by Pettenkofer's test, 

 which consists in the production of a red color, changing to purple 

 or violet, on the addition of cane sugar and sulphuric acid. The test 

 is applied in the following way : One part of cane sugar is dissolved 

 in four parts of water. Of this liquid, one drop is added to each cubic 

 centimetre of the solution of biliary salts. On treating the mixture 

 with a few drops of pure sulphuric acid, the biliary acids are decom- 

 posed, forming cholic acid. If the biliary salts be present in a propor- 

 tion of not more than one part in 500, the solution remains clear : if 

 in larger quantity, the cholic acid is precipitated, forming a whitish 

 turbidity. This turbidity is again cleared up on the continued addition 

 of sulphuric acid ; and in the course of a few minutes a cherry-red 

 color appears, changing rapidly to a violet, and subsequently, if the 

 biliary salts be present in the proportion of one part in 500 or over, 

 to a deep rich purple. In very dilute solutions, the violet or purple 

 color may not be distinctly visible before the end of an hour. 



The precautions required in the use of this test are as follows: 

 First, the liquid to be examined should be free from other organic sub- 

 stances, particularly albuminous and coloring matters. For this purpose, 

 it should be evaporated to dryness, the dry residue extracted with 

 absolute alcohol, the alcoholic solution decolorized, if necessary, with 

 animal charcoal, then precipitated with ether in excess, and the ether 

 precipitate dissolved in water. This gives a clear, colorless solution, 

 free from organic contamination. Secondly, as the solution becomes 

 heated by the liberal admixture of sulphuric acid, its temperature 

 should not be allowed to rise above 70 C., nor to fall much below this 



