I Q2 PHYSIOLOGICAL CHEMISTRY 



that fats can be absorbed only in water-soluble form and that saponi- 

 fication is a necessary preliminary to absorption." Petroleum hydro- 

 carbons and non-saponinable esters, e.g., wool fat (lanolin) were un- 

 absorbed. Bloor further claims 1 that in the absorption of fats there is 

 a tendency toward the formation of a uniform chyle fat, presumably the 

 characteristic body fat of the animal. 



Pancreatic lipase is very unstable and is easily rendered inert by the 

 action of acid> For this reason it is not possible to prepare an extract 

 having a satisfactory fat-splitting power from a pancreas which has 

 been removed from the organism for a sufficiently long time to have 

 become acid in reaction. 



The fourth enzyme of the pancreatic juice is called pancreatic rennin. 

 It is a milk-coagulating enzyme whose action is very similar to that 

 of the gastric rennin found in the gastric juice. It is supposed to show 

 its greatest activity at a temperature varying from 60 to 65C. 



PREPARATION OF AN ARTIFICIAL PANCREATIC JUICE 2 



After removing the fat from the pancreas of a pig or sheep, finely divide the 

 organ by means of scissors and grind it in a mortar. If convenient, the use of an 

 ordinary meat chopper is a very satisfactory means of preparing the pancreas. 



When finely divided as above the pancreas should be placed in a 500 c.c. 

 flask, about 150 c.c. of 30 per cent alcohol added and the flask and contents-shaken 

 frequently for 24 hours. (What is the reaction of this alcoholic extract at the end 

 of this period, and why?) Strain the alcoholic extract through cheese cloth, 

 filter, nearly neutralize with potassium hydroxide solution and then exactly 

 neutralize it with 0.5 per cent sodium carbonate. 



Products of Tryptic Digestion 



Introduce into a 250 c.c. flask 20 grams of casein, 10 c.c. of the artificial 

 pancreatic juice prepared as described above and 100 c.c. of i per cent sodium 

 carbonate. Allow to digest at 4OC. for 8 to 10 days with the addition of a 

 few cubic centimeters each of chloroform and toluene, the flask being stoppered 

 with cotton. As the chloroform and toluene evaporate they must be renewed. 

 Heat the mixture to boiling and at the boiling-point add acetic acid drop by drop 

 until the mixture is acid in reaction. Cool and filter. 



To five c.c. of the filtrate add bromine water drop by drop. Note the develop- 

 ment of pink color which disappears hi the presence of an excess of the reagent. 

 This reaction indicates the presence of tryptophane. 3 



To another 5 c.c. portion of the filtrate add 10 drops of concentrated sulphuric 

 acid and 10 c.c. of a 10 per cent solution of mercuric sulphate hi 5 per cent sul- 

 phuric acid. After mixing and allowing to stand for a few minutes filter off 

 the yellow precipitate which forms. This is a mercury compound of tryptophane. * 



'Bloor: Jour. Biol. Chem., 16, 517, 1914. 



* For other methods of preparation see Karl Mays: Zeitschrift fur physiologischc Chemie, 

 38, 428, 1903. 



3 Kurajeff: Zeit. physiol. Chem., 36, 501, 1898-99. 



4 It has been claimed that a similar yellow precipitate forms in the presence of tyrosine. 

 cystine and polypeptides. For quantitative estimation of tryptophane see Homer: Jour, 

 Biol. Chem., 22, 369, 1915. 



