94 II. DIGESTION AND ABSORPTION OF FATS 



not arise through a rupture of the original ring by pyrolysis, but that the 

 acid was in a molecular combination with desoxycholic acid. 



(6) General Properties. Choleic acid was found to contain 8 molecules 

 of desoxycholic acid associated with one molecule of fatty acid. The 

 complex was shown to dissolve in alkali without decomposition. A similar 

 compound could be produced synthetically by allowing crystallization to 

 occur from an alcoholic solution of desoxycholic acid and stearic acid. 

 It has a sharp melting point (186°C), which is appreciably higher than that 

 of desoxycholic acid or of stearic acid. The stearic acid was found to be 

 bound so firmly that it could be split off only with difficulty as, for example, 

 by transformation of the complex into products which were dehydrated or 

 oxidized. There is no explanation as to how this change can be mediated 

 in the animal body. 



According to von Fiirth and Minibeck, 512 Chiray and Cuny have deter- 

 mined that the ratio of bile acids to fat, fatty acids, and phosphatides 

 varies between 1 : 8 and 1 : 24 in the case of children, between 1 : 6 and 1 : 20 

 in cats, and from 1 : 1.5 to 1 :5 in rats. According to these results, the bile 

 salts are very economically used in the intestinal absorption of these lipids. 

 It has been suggested that the bile acids function by forming an adsorption 

 layer on the intestinal membranes which acts like a turnstile in admitting 

 the fatty acids through the membrane. Such a conception would explain 

 the relatively small amount of bile salts used in the absorption of large 

 quantities of the lipids. 512 Verzar and Kuthy 513 believe that they have 

 proved the existence of choleic acids in solution. Although the minimum 

 pH values for obtaining clear soap solutions with oleate, palmitate, and 

 stearate were found to be 8.1, 9.1, and 9.0 respectively, this condition 

 could be effected in the presence of conjugated bile salts at pH values of 

 0.18, 6.35, and 6.16, respectively. Thus, conjugated bile acids are able to 

 maintain solution and diffusion on the acid side of neutrality in a pH range 

 where the unconjugated bile acids do not dissolve. 



(c) Occurrence and Types of Choleic Acids. There is every reason to 

 believe that the "choleic acid principle" extends to lipids other than the 

 fatty acids. 514 It is known that the absorption of ingested cholesterol as 

 well as of that secreted by the intestinal mucosa requires bile. 515 " 517 Des- 

 oxycholic acid is an excellent solvent for cholesterol; it was shown that a 



512 O. von Fiirth and H. Minibeck, Biochem. Z., 237, 139-158 (1931). 



5,3 F. Verzar and A. Kuthv, Biochem. Z., 205, 369-379 (1929); 210, 265-280 (1929). 



514 J. A. Gardner and H. Gainsborough, Quart. J. Med., 23, 465-483 (1930). 



515 M. A. Rothschild and A. O. Wilensky, Am. J. Med. Sci., 156, 239-247 (1918). 



516 H. Salomon and L. L. Silva, Arch. Verdauungskrankh., 36, 353-359 (1926): Biol. 

 Abst., 1, 468(1927). 



617 H. Beumer and F. Hepner, Z. ges. exptl. Med., 6/ h 787-797 (1929). 



