30 



130. Divide the above into two parts. To one part add a 

 little dilute acetic acid, if there is no precipitate it indicates- 

 that the caseinogen has been converted into peptones. To 

 the other part apply the biuret reaction for peptones. 



131. With the reserved portion from the fibrin and albu- 

 min tubes (117), if digestion has been thorough, some 

 further products may be found. 



Dip the uncovered end of a wooden match in hydrochloric 

 acid and then into the fluid from the fibrin tube. Repeat 

 for the albumin. If the match is stained red from either 

 fluid it indicates the presence of indol, one of the putrefactive 

 products of pancreatic digestion. 



132. Take equal parts of Millon's reagent and the respec- 

 tive fluids and boil together. A port wine color may appear. 

 If so tyrosin is present. Tyrosin (and l,euciu) represent 

 digestive products beyond peptones. They do not occur in 

 gastric digestion. 



XII. 



133. Bile. The bile used in the.se experiments has been 

 obtained from an ox. Its color is greenish, that of man is 

 brownish yellow. In pouring the bile from one vessel to 

 another note that strings of so-called mucin are present. 

 The mucin of bile is not formed in the liver but in the 

 mucous glands of the gall-bladder and duct, the longer the 

 bile has been in the gall-bladder the greater the precipitate 

 which will be obtained. For general use the bile maj' be 

 diluted 2-4 times with 0.1% formalin. The formalin 

 will preserve the bile indefinitely. 



134. Test the reaction of bile with litmus paper. 



135. To a little bile in a test-tube add some strong alcohol. 

 This produces a precipitate of mucin with some pigment en- 

 tangled. 



136. Mucin is also precipitated by the addition of acetic 

 acid to bile. Perform this test. Filter off the mucin. 



