559 



TJie Origin and Destiny of Cholesterol in the Animal Organism. 

 Part VII. — On the Quantity of Cholesterol and Cholesterol 

 Esters in the Blood of Rabbits Fed on Diets containing Vary- 

 ing Amounts of Cholesterol. 



By Mary T. Eraser, B.Sc, and J. A. Gardner, M.A. 



(Communicated by Dr. A. D. Waller, F.R.S. Received June 17, — Read 



June 30, 1910.) 



(From the Physiological Laboratory, University of London, South Kensington.) 



From the study of the inhibitory action of the sera of rabbits fed on diets 

 containing varying amounts of cholesterol on the haemolysis of blood by 

 saponin vfc were led to the conclusion, in an earlier paper* of this series, 

 that when cholesterol, free or in the form of esters, is given with the 

 food of rabbits some is absorbed and finds its way into the blood stream 

 as free cholesterol ; and also that when phytosterol is used instead of 

 cholesterol it behaves similarly, and some appears in the blood either 

 itself or in the form of cholesterol. The method adopted in these experi- 

 ments only gave information as to the amount of free cholesterol under 

 various conditions, ljut not as to the amount of cholesterol esters that 

 might be present. It seemed to us desirable to confirm these results by 

 a chemical method, and also, if possible, to estimate both the free cholesterol 

 and the esters present at the same time in the blood under various 

 conditions. 



The usual methods for the chemical estimation of cholesterol are not 

 sufficiently accurate to give reliable information in the case of a fluid such as 

 blood, which contains but a small percentage of cholesterol, and which is 

 only available in relatively small quantities. The discovery of Windausf 

 in 1909 that cholesterol, but not cholesterol esters, readily combines 

 quantitatively with digitonin to form a highly insoluble compound, digitonin 

 cholesteride, according to the following equation — 



C55H94O28 + C27H46O = C82H140O29, 



afforded a means of solving the problem. 



According to Windaus, digitonin cholesteride is insoluble in water, acetone, 

 ether, ethyl acetate and benzene. 100 c.c. ethyl alcohol (95 per cent.), 



* ' Eoy. Soc. Proc.,' 1909, B, vol. 81, p. 230. 



t "Windaus, " TJber die Entgiftung der Saponine durch Cholesterin," ' Ber. der Deut. 

 Chem. Ges.,' 1909, vol. 42, pt. 1, p. 238. 



