442 CHOLESTERIN. [BOOK I. 



Thudi- Under the name of cerebrins, Thudichum describes a 



chum's re- class of nitrogenous bodies free from phosphorus, which 



searches on^ -^ Q believes to exist in the brain. Certain of these bodies he 

 obtained by following substantially Miiller's process ; others 

 by extracting brains with alcohol at 45 C., and purifying the substance ob- 

 tained by various solvents. He believes Miiller's cerebrin to be the lowest 

 representative of a group of nitrogenous prinicples of the brain which 

 are free from phosphorus, contain nitrogen, and vary in the number 

 of carbon atoms which they contain, for each nitrogen atom, between 

 17 and 48. "Whatever may be the ultimate explanation of these differ- 

 ences of composition must be left for future inquiry. Meanwhile it is 

 certain that these differences do but slightly affect the external appearance 

 and bearing towards solvents of these bodies, so that by describing 

 the general properties of one we describe the general properties of all 

 members of the group, while differentiating characters and means are most 

 difficult of discovery and application." 



"The cerebrins are all soluble in hot alcohol, particularly in absolute 

 alcohol, and deposited on cooling; they are very little soluble in cold 

 absolute alcohol, much less soluble indeed than myeline, which can thus be 

 separated from the cerebrins. The mixture is dissolved in hot alcohol and 

 allowed to cool j nearly all cerebrin falls down, much myeline remains in 

 solution. The deposit is separated from the liquid, and subjected to this 

 treatment until it is free from phosphorus." 



The following are the three chief bodies which Thudichum classes amongst 

 the cerebrins. 



Cerebrin C^H^O, (Mailer). 



Phrenosine C^H^NOg. 



Kerasine C^ELNOo. 



SECT. 6. CHOLESTERIN (C 26 H 44 + H 2 0). 



Amongst the most abundant of the constituents of the nervous 

 tissues, and especially of the white matter, is the beautiful, crystalline, 

 non-nitrogenous, body cholesterin. This body, which is very freely 

 soluble in ether, cold or hot, is also freely dissolved by warm alcohol, 

 which in great part deposits it on cooling; in consequence of its solu- 

 bility in these two fluids, cholesterin finds its way into both the 

 ethereal and alcoholic extracts of the nervous tissues 2 . 



Prepara- The tissue from which cholesterin is to be extracted 



tion of cho- may be placed in cold alcohol for some days, so as 

 lesterin from to deprive it of the greater part of its water. The 

 SP1 " hardened substance is then finely divided and digested 

 in boiling alcohol. The alcoholic solution is filtered 



1 Thudichum, " Eesearches on the Chemical Constitution of the Brain." Reports 

 of the Medical Officer of the Privy Council and Local Government Board, London, 187-1, 

 pp. 113247. 



2 The author some years ago performed a number of experiments with the object of 

 determining whether cholesterin preexists in the nervous tissues or is merely one of the 

 products of the decomposition of more complex bodies. These experiments led him to 

 the conclusion that cholesterin exists preformed in the brain. 



