92 II. DIGESTION AND ABSORPTION OF FATS 



fats is its ability to produce emulsification of fats. 499 Haller first recog- 

 nized this emulsifying property of bile many years ago, although unre- 

 corded observations must frequently have been made of this behavior 

 before the time of Haller. It is now known that, in addition to the bile 

 acids, the phospholipids and soaps in bile contribute to the emulsifying 

 activity. However, the action of bile salts does not seem to be due merely 

 to an improved emulsification, inasmuch as Tidwell and Nagler, 500 as well 

 as Annegers, 501 demonstrated that other emulsifiers are ineffective in im- 

 proving absorption. 



However, the most important action of bile in facilitating the absorption 

 of lipids from the gastrointestinal tract is to be traced to the production 

 of water-soluble coordination compounds of the fatty acids with the bile 

 salts. Such "choleic acids" enable the fatty acids to diffuse through the 

 walls of the mucosa cells lining the gut into the aqueous medium existing 

 there. 



A hitherto unsuspected action on the part of the bile salts on intestinal 

 digestion is their effect on intestinal motility. Meyer and McEven 502 

 reported that conjugated bile acids, desoxycholic acid and cholic acid, as 

 well as the choline salts of these latter two acids, and choline itself, exert 

 analogous effects on the small and large intestine of the guinea pig, when 

 applied to the internal surface. Low doses were shown to cause stimula- 

 tion of the rhythmic movements, while higher doses tended to produce an 

 increased tonus, thus counteracting the wave movements. Bile salts had a 

 greater tendency to stimulate the oscillatory movements, while choline had 

 a stronger effect on tonus. Conjugated bile salts were shown to have the 

 weakest action, cholic acid a somewhat stronger influence, while desoxy- 

 cholic acid produced the strongest effect. While choline itself tended to 

 produce a spastic arrest of the gut movements, the choline salts of the bile 

 acids principally maintained a slow longitudinal and peristaltic movement 

 at a high tonus. It is not known whether or not these effects are mediated 

 by the bile salts under ordinary conditions. 



a. Choleic Acids and Related Coordination Compounds. The solvent 

 action of bile salts on the fatty acids was demonstrated by Moore and 

 Rockwood 503 in 1896. It was shown that, whereas oleic acid was soluble 

 to the extent of 4-5% in ox bile, stearic acid was much less soluble. How- 



499 C. G. Lehmann, Lehrbuch der physiologische ('hemic, Leipzig, 1850, 2nd ed., trans- 

 lated by J. C. Morris, Blanchard & Lea, Philadelphia, J 856, pp. 173-174, 254. 

 «» H. C. Tidwell and M. E. Xagler, Proc. Soc. Exptl. Biol. Med., SI, 12-15 (1952). 



501 J. H. Annegers, Proc. Soc. Exptl Biol. Med., 81, 277-278 (1952). 



502 A. E. Meyer and J. 1'. McEven, Am. J. Physiol., 153, 386-392 (1948). 



503 B. Moore and D. V. Rockwood, Proc. Roy. Soc. London, 60, 438-4 12 (1896). 



