Destiny of Cholesterol in the Animal Organism. 361 



analyses of samples of each food consumed by each set of subjects were 

 made, no figures published in the literature being made use of. This was 

 very necessary, as there was reason to suppose that war-time conditions of 

 under-feeding might have an effect on the composition of various articles of 

 the diet, particularly milk and meat. 



Methods of Analysis. 



The faeces were analysed in the following manner. A weighed portion of 

 the dried faeces was subjected to a prolonged extraction in a Soxhlet 

 apparatus with ether, and the ethereal solution was made up to known 

 volume. Aliquot portions were then respectively titrated with standard 

 alcoholic caustic soda, and evaporated to dryness and weighed. The rest of 

 the ethereal solution was then mixed with a hot alcoholic solution of a very 

 large excess of sodium, and allowed to stand forty-eight hours. The pre- 

 cipitated soaps were then filtered on the pump and thoroughly washed with 

 ether. The ethereal filtrates and washings were then repeatedly shaken 

 with alkaline water, and finally with distilled water, until quite free from 

 soap. The ethereal solution of unsaponifiable matter thus obtained was 

 made to known volume, and a suitable aliquot portion evaporated to dryness 

 and weighed. The weighed unsaponifiable matter was then dissolved in 

 alcohol, and the boiling solution mixed with a hot 1 per cent, alcoholic 

 solution of digitonin, using at least a 10 per cent, excess, and allowed to 

 stand overnight for the insoluble sterol-digitonides to separate. The alcohol 

 was then evaporated at the lowest convenient temperature, and the residue 

 washed by decantation with ether or light petroleum, to separate the portion 

 of the unsaponifiable matter not precipitated by digitonin. The ether 

 washings were passed through a weighed Gooch crucible, to guard against 

 any loss of sterol-digitonide. The mixture of digitonide and excess of 

 digitonin was then freed from the latter by washing by decantation with 

 warm water, and finally the sterol-digitonide was brought into the Gooch 

 crucible and the washing completed. The digitonide was then dried at 110° 

 and weighed. 



It was found advantageous to cover the asbestos mat of the crucible with 

 a layer of pure sand. This prevented to some extent the sterol-digitonide 

 from forming an impervious cake on the surface of the asbestos, and thus 

 facilitated the filtration and washing. It was also very desirable to evaporate 

 the alcohol before washing the digitonides, owing to the fact that the 

 digitonides of both coprosterol and yS-cholestanol are considerably more 

 soluble in alcohol than cholesterol-digitonide. 



The weight of sterol-digitonide, x 0"234, equals the weight of sterol in the 



2 E 2 



