372 ON THE CHOLESTERIN-ESTERS 



In his contributions to the chemistry of the blood, Hoppe- 

 Seyler * has recorded analyses of the blood of the goose which 

 indicate that cholesterin is present in the serum of this species 

 in quantities approaching those of the ox. 



In the course of some experiments in this laboratory, on the 

 chemistry of birds' blood, the blood-serum of the hen, turkey, 

 goose, and duck has been examined for cholesterin-esters. 

 The observations made are recorded briefly here, since they 

 verify and extend the investigations of Hiirthle, whose 

 methods have been employed, for the most part, in the prepa- 

 ration of the esters. The blood-serum was usually precipitated 

 with three volumes of alcohol ; after standing, the precipitate 

 was filtered off and extracted with fresh alcohol for two or 

 three days at 40 C. Good results were obtained by keeping 

 the precipitate continually agitated in the warm alcohol by 

 means of a slow current of air. The filtered extract deposited 

 the characteristic small needle crystals of the oleate on stand- 

 ing in the cold, while the surface of the alcohol was usually 

 covered with a slight film having a more or less crystalline 

 character (cholesteryl palmitate). The film was separated as 

 far as possible, and the larger mass of fine needle crystals, 

 often grouped in rosettes, was filtered off, washed with cold 

 alcohol, and dried in vacuo over sulphuric acid. The crystals 

 thus obtained were weighed, in order to afford an approximate 

 idea of the quantity of material obtainable from the various 

 serums ; this method, as Hiirthle has observed, by no means 

 gives accurate determinations, inasmuch as quite appreciable 

 quantities of the corresponding ester remain in solution hi the 

 alcohol used. The precipitated serum residues were usually 

 re-extracted with warm alcohol, and finally treated with 

 alcohol-ether for the separation of the remaining cholesteryl 

 palmitate. The yield of substance in the latter process was 

 always small. The ester preparations obtained were purified 

 by recrystallization from alcohol, until the melting points cor- 

 responded with those found by Hiirthle. In some cases the 

 composition of the product was further established by an 



* Hoppe-Seyler, loc. cit., p. 145. 



