Origin and Destiny of Cholesterol in the Animal Organism. 359 



It has been shown by one of us (1921) that though the crystalline sterols 

 of human adult fseces consist mainly of coprosterol, there are also present 

 smaller quantities of /3-cliolestanol, cholesterol, and possibly phytosterol, 

 derived from the vegetable food. These substances can be quantitatively 

 precipitated together from alcohol solution in the form of their digitonides, by 

 means of an alcoholic solution of digitonin, and so estimated. 



There is, however, no simple method by which the quantitative composi- 

 tion of the mixture of sterols recovered from the mixed digitoilides can be 

 determined. If a sufficient quantity of material is available, the bulk of the 

 coprosterol may be separated by fractional crystallisation. The jS-cholestanol 

 may be separated from the coprosterol by conversion of the latter into 

 A^-coprosterol, which does not form a compound with digitonin, and the 

 isolation of the unchanged ;8-cholestanol in the form of its digitonide. 

 Cholesterol (with phytosterol) may be approximately estimated as dibromide. 



These crystalline sterols, precipitable by digitonin, constitute only a pro- 

 portion of the unsaponifiable matter of fseces, the rest may be washed away 

 by means of ether or light petroleum from the precipitated digitonides and 

 obtained as a reddish brown oil. This oil can be distilled, without any 

 decomposition, in superheated steam and passes over into the condenser in 

 the form of a solid emulsion, which is forced from the condenser, partly by 

 the pressure of steam and partly by the action of the condensed water, in the 

 form of solid white candles. These persist for a long time, but usually 

 separate on long standing into oil and water. This oil can be distilled in a. 

 vacuum of 1 mm. without decomposition and passes over in a series of 

 fractions ranging from 100° to 220°. The lower fractions contain aliphatic 

 alcohols of high molecular weight, of which cetyl alcohol has been definitely 

 identified. These fractions do not give any colour reaction with acetic 

 anhydride and sulphuric acid. The higher fractions, boiling 200° — 220°^ 

 under 1 mm,, constitute the main bulk of the oil. They are usually obtained 

 in the form of transparent yellow glass, melting at 16° — 18° C. and showing 

 in bulk a greenish fluorescence. These glassy substances are marked by great 

 stability, contain oxygen in a not very reactive form, and have a molecular 

 composition of much the same order as cholesterol (Gardner, 1921). 



They give the Burchardt-Liebermann reaction with acetic anhydride and 

 sulphuric acid in a well-marked, though modified, manner, and though nO' 

 crystalline esters have been prepared, they appear to be alcohols of a poly- 

 cyclic type. 



In view of the above facts, it seemed to us desirable to investigate more 

 fully the intake and output of sterols in the case of normal human subjects, 

 on a rigidly known diet. For this purpose we made use of some of the 



VOL. xcii. — B. 2 E 



