60 CHEMICAL PHYSIOLOGY. 



watery extract of the fresh pancreas, and do likewise ; but 

 in this case the result will not be nearly so satisfactory. 



(b.) Rub up oil as in (a.); but this time use an extract of 

 the fresh pancreas made with 1 per cent, sodic carbonate. 

 A very perfect emulsion is obtained, even if the sodic 

 carbonate extract is boiled beforehand. This shows that 

 its emulsifying power does not depend on a ferment. 



(c.) The presence of a little free, fatty acid greatly favours 

 emulsitication. Take two samples of cod-liver oil, one 

 perfectly neutral (by no means easily procured), and an 

 ordinary brown oil e.g., De Jongh's. The latter contains 

 much free fatty acid. Place 5 cc. of each in two test-tubes, 

 and pour on them a little solution of sodic carbonate (1 per 

 cent.) The neutral oil is not emulsified, while the rancid 

 one is at once, and remains so. Many oils that do not 

 taste rancid contain free fatty acids, and only some of them 

 give up their acid to water, just according as the fatty acid 

 is soluble in water, or not. 



7. B. The Fat-Splitting Action of Pancreatic Juice. 



(a.) Prepare a perfectly neutral oil. A perfectly neutral 

 oil is required, and as all commercial oils contain free fatty 

 acids, they must not be used. Place olive or almond oil in 

 a porcelain capsule, mix it with not too much baryta 

 solution, and boil for some time. Allow it to cool. The 

 unsaponified oil is extracted with ether, the ethereal extract 

 separated from the insoluble portion, and the ether evaporated 

 over warm water. The oil should now be perfectly neutral 

 (Krukeriberg). 



(b.) Mix the oil with finely-divided, perfectly fresh pan- 

 creas (not a watery extract), and keep it at 40 C. After a 

 time its reaction becomes acid, owing to the formation of a 

 fatty acid. This experiment is by no means easy to perform, 

 and some observers deny altogether the existence of a fat- 

 splitting ferment. The free fatty acids thus liberated unite 

 with the alkaline bases of bile, and form soaps. 



8. IV. Milk- Curdling Ferment. 



(a. ) Add a drop or two of the brine extract of the pan- 

 creas prepared for you, to 5 cc. of warm milk in a test-tube, 



