84 PRACTICAL PHYSIOLOGY. [X. 



(/>.) Rub up oil as in (a.) ; but this time use an extract of the fresh pancreas 

 made witli i j)er cent, sodic carbonate. A veiy 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 /(Uty acid greatly favours emidsification. 

 Take two samples of cod-liver oil, one perfcrHy neutral (by no means easily 

 procured), and an ordinary brown o\\.—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 (i 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 or not in water. 



8. (B.) The Fat-Splitting Action of Pancreatic Juice (Steapsin 

 or pialyn, the ferment). 



(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 {Krukcnhcrg). 



{b.) Mix the oil with finely divided, perfectly fresh pancreas (not a watery 

 extract), and keep it at 40'' C. After a time its reaction becomes acid, owing 

 to tlie formation of a fatty acid. This experiment is by no means easy to per- 

 form, and some observers deny altogether the existence of a fat-splitting 

 fennent. The free fatty acids thus liberated unite with the alkaline bases of 

 bile, and form soaps. 



9. IV. Milk-Curdling Ferment. 



(a.) Add a drop or Uvo of the brine extract of the pancreas pre- 

 pared for you to 5 cc. of warm milk in a test-tube, and keep it at 

 40° C. Within a few minutes a soHd coagulum forms, and there- 

 after the whey begins to separate. 



(A.) Repeat (a.), but add a grain or less of bicarbonate of soda to 

 the milk. Coagulation occurs just as before, so that this ferment 

 is active in an alkaline medium. 



(c.) Boil the ferment first. Its power is destroyed. 



10. Action on Milk. 



(a.) Place cow's milk diluted with 5 volumes of water in a test- 

 tube, add a drop or two of pancreatic extract or liquor pancrea- 

 ticiis. Keep at 40° C. for half an hour. The caseinogen is first 

 curdled and then dissolved, and as this occurs, the milk changes 

 from a white to a yellowish colour. 



(/>.) Divide (a.) into two portions, A and B. To A add dilute 

 acetic acid ; there is no precipitation of caseinogen, which has been 

 converted into peptones. To B add caustic soda and dilute copper 

 sulphate, wliich give a rose colour, proving the presence of peptones. 



