,162 -: :*: : cy$LO&E& CHOLESTEROL AND CHOLIC ACID 



comparative difficulty with which they are hydrolyzed or "saponified" 

 by alkalies, in their resistance to the action of bacteria, so that they do 

 not become "rancid," and in the property they possess of absorbing 

 or mechanically imbibing a large proportion of water to form a mass 

 which still retains a fatty consistency. For this reason lanoline has 

 of late come to be employed very widely in therapeutics as a vehicle 

 for aqueous solutions of drugs which, through this agency, may be 

 applied as salves. 



The cholesterol esters differ from cholesterol is not being emulsi- 

 fiable in water containing soaps. Acetyl cholesterol C^yELs.OOC.CHs 

 is also devoid of the characteristic action of cholesterol upon the 

 growth of carcinomata. It would seem unlikely that this is due merely 

 to the replacement of a hydroxyl-group by an acetyl-group, more 

 especially since a variety of soluble and insoluble hydroxyl-derivatives 

 of hydroaromatic substances have been found to be devoid of action 

 upon the growth of carcinoma. It appears more likely that the loss 

 of emulsifiability consequent upon the replacement of the hydroxyl- 

 group prevents the distribution of acetyl cholesterol by the blood and 

 tissue-fluids to the cells of the carcinomatous tissue. 



The cholesterol esters are of exceptional interest to the physical 

 chemist because they are the substances which were first observed by 

 Lehmann to display the remarkable phenomenon of "fluid crystals" 

 or drops which, while spherical and retaining the characteristics of 

 fluids, nevertheless display evidence, afforded by the unequal refrac- 

 tion of light in different axes, of the possession of an internal crystalline 

 structure. While other bodies are now known which display this 

 peculiarity, the cholesterol esters still constitute a group which is pre- 

 eminently suitable for the investigation of fluid crystals. They may 

 be very readily obtained by gently heating the esters on a microscope 

 slide until somewhat above the melting-point, and allowing to cool to a 

 little above the melting-point. 



According to Adami fluid crystals, presumably containing choles- 

 terol esters, may be observed in the myelin droplets which form during 

 the degeneration of the fatty sheaths of medullated nerves. 



THE BILE-SALTS AND CHOLIC ACID. 



The mixed bile-salts, sodium glycocholate and sodium taurocholate 

 may readily be obtained from ox-bile by mixing the bile with animal 

 charcoal, evaporating to dryness, extracting with hot alcohol and add- 

 ing ether to the cooled extract. If the process has been properly per- 

 formed, a snow-white precipitate of fine acicular crystals ("Plattner's 

 crystallized bile") is obtained which, in one or two crystallizations, 

 may be almost freed from contamination. The two salts may be 

 separated by adding lead acetate to their aqueous solution, by which 

 means the glycocholate is precipitated, while the ta irocholate 

 remains in solution. Sodium glycocholate is the most abundant 



