132 CHOLESTERIN. 



tained only from spermaceti.) It is a glittering white crystalline 

 substance, soapy to the touch, crystallising in fine needles from 

 its solution in ether, chloroform, or benzol ; from its hot alcoholic 

 solutions it is deposited on cooling in rhombic tables ; this is the 

 characteristic form and of great importance for the identification 

 of cholesterin. 



Fig. 5. CHOLESTEKIN CKYSTALS. (After Funke.) 



When dried it melts at 145, and distils in closed vessels at 

 360. It is quite insoluble in water and in cold alcohol, but 

 soluble in solutions of bile salts. 



Solutions of cholesterin possess a left-handed rotatory action 

 on polarised light, (a) D = -3'5 in ethereal solution, =- 37 in 

 chloroforrnic. 



Cholesterin occurs in small quantities in the blood and many 

 tissues, and is present in abundance in the white matter of the 

 cerebro-spinal axis and in nerves. It is a constant constituent of 

 bile, and forms frequently nearly the whole mass of some gall- 

 stones. It is found in many pathological fluids, hydrocele, the 

 fluid of ovarial cysts, &c., also in faces and milk. 1 It also oc- 

 curs in the substance of the crystalline lens, more especially in 

 ' cataract.' 



Preparation. Gall-stones supply the most convenient source 

 of cholesterin. These are pounded, extracted with boiling water 

 and dissolved i-n boiling alcohol. The solution is filtered through 

 a heated filter, and the cholesterin separates out in a fairly pure 

 condition as the filtrate cools. It is purified by resolution in boil- 

 ing alcohol to which some caustic soda has been added ; from this 

 it again separates on cooling, and is finally washed with cold al- 

 cohol and water. 



1 Tolmatscheff, Hoppe-Seyler's Med. Chem. Untersuch. Hf. 2 (1867), S. 272. 

 Schmidt-Mulheim, Pfliiger's Arch. Bd. xxx. (1883), S. 384. 



