CHOLESTERIN. 153 



tion of his Dictionary of Chemistry, published in 1778, notices 

 cholesterin as a singular substance, and gives some of its proper- 

 ties, and informs us, that it was discovered by the author of the 

 French translation of the London Pharmacopoeia.* This was 

 Poulletier de la Salle. In 1834, Couerbe showed that it exists 

 also as a constituent of the brain ; though between that in the 

 brain and in human gall-stones there are some differences which 

 we shall point out at the end of this section. 



Cholesterin may be obtained in a state of great purity by di- 

 gesting human gall-stones in boiling alcohol, drawing off the 

 clear solution, and leaving it to cool. The cholesterin is depo- 

 sited in beautiful crystalline plates. It may be obtained from 

 bile by the following process : 



Evaporate the bile to the consistence of a thick extract ; agi- 

 tate this extract several times in succession with ether, till that 

 liquid ceases to extract any thing from it. Mix all these ethe- 

 rial liquids, and draw off the greatest part of the ether by distil- 

 lation. The residue, on cooling, deposites crystals of cholesterin, 

 mixed with some oleic acid. This may be got rid of either by 

 digesting the impure cholesterin with dilute caustic alkali, which 

 dissolves the oleic acid, and leaves the cholesterin pure ; or, by 

 dissolving the impure crystals in boiling alcohol, as the solution 

 cools, the cholesterin is deposited in crystals, and in a state of 

 purity. 



Cholesterin crystallizes in beautiful white plates, having a 

 pearly lustre. It has some resemblance to spermaceti, but is 

 more beautiful. It has neither taste nor smell. It is lighter than 

 water, and when heated to 278, it melts into a liquid as colour- 

 less as water. On cooling, it concretes into a foliated crystalline 

 mass, translucent, and capable of being reduced to powder. But 

 the powder attaches itself strongly to every body with which it 

 comes in contact. When distilled per se in a retort, (air being 

 excluded,) it mostly passes over unaltered, and is deposited in 

 crystalline plates. But if air have free access, the cholesterin 

 undergoes decomposition, assumes a brown or yellow colour, and 

 a considerable quantity of empyreumatic oil is formed, which holds 

 a portion of cholesterin in solution. According to Kiihn,f if we 

 heat cholesterin in a glass-tube till a portion of it sublimes, and 



* Macquer's Diet. i. 501. f Diss. de Cholesterine. Leipsik, 1828. 



