OLEOMARGARINE. 137 



after being acted upon by the pepsine of the gastric juice, are still 

 further broken up. The pancreatic juice, so far as is known, is the 

 chief agent in bringing about these changes. The bile does nothing 

 more than to aid in neutralizing the acidity and thus prepare them for 

 the action of the pancreatic juice. But with fat it becomes an impor- 

 tant factor. Its salts unite with any free fatty acid and form soaps. 

 It also dissolves soaps which, as we shall see hereafter, materially aid 

 the pancreatic fluid in its action upon fats. Bile also has some emul- 

 sifying power on fats. A soap is a fat acid united with a base, as 

 soda, potash, etc. 



"The pancreatic juice has a powerful emulsifying effect upon fats; 

 that is, divides them into very minute particles. It also has the power, 

 to some extent, of breaking them up into their fatty acid and glycerin; 

 and if an alkali is present the fatty acid unites with it to form soap. 



"As we have alread} 7 stated, bile has a slight emulsionizing and sol- 

 vent effect upon fat, but the fact which is known to be the most impor- 

 tant in its relation to the digestion of fat is that it unites with the free 

 fatty acids which are present in the chyme and forms soaps. It also 

 dissolves soaps that may have been formed before reaching it; and the 

 presence of soluble soaps are known to aid the emulsion of fats. 



' ' Foster says in reference to this : ' Thus a rancid fat i. e. , a fat 

 containing a certain amount of free fatty acid forms an emulsion with 

 an alkaline fluid more readily than does a neutral fat. A drop of ran- 

 cid oil let fall on the surface of an alkaline fluid, such as a solution of 

 sodium carbonate of suitable strength, rapidly forms a broad ring of 

 emulsion and that even without the least agitation. As saponification 

 takes place at the junction of the oil and alkaline fluid currents are set 

 up by which globules of oil are detached from the main drop and 

 driven out in a centrifugal direction. The intensity of the currents 

 and the consequent amount of emulsion depend on the concentration 

 of the alkaline medium and on the solubility of the soaps which are 

 formed; hence some fats, such as cod-liver oil, are much more easily 

 emulsionized in this way than others. Now, the bile and pancreatic 

 juice supply just such conditions as the above for emulsionizing fats; 

 they both together afford an alkaline medium. The pancreatic juice 

 ^ives rise to an adequate amount of free fatty acid, and the bile in 

 addition brings into soluti'on the soaps as they are formed. So that 

 we may speak of the emulsion of fats in the small intestine as being 

 carried on by the bile and pancreatic juice acting in conjunction, and, 

 as a matter of fact, the bile and pancreatic juice do largely emulsify 

 the contents of the small intestine, so that the grayish turbid chyme 

 is changed into a creamy-looking fluid, which has been sometimes 

 called chyle.' 



"Now, we believe that butter fat is especially fitted to supply these 

 conditions. Butter, as is well known, readily becomes rancid, and, 

 no doubt, butter contains some free acid very shortly after being made; 

 but we will consider a perfectly fresh specimen. According to Lang, 

 the first step in the decomposition of butter is a conversion of lactic 

 acid into butyric. The second is the breaking up of butyrin into 

 butyric acid and glycerin, the butyrin furnishing by far the most 

 free acid about 7 per cent. Thus we see that the first fat in the 

 mixture of butter to break up outside of the body is butyrin, and 

 doubtless this is the case inside. 



" J. Bell asserts that when a solution of alcohol and an alkali is used 



