BY E. C. GREY. 



299 



The following figures give the total fatty acids and cholesterol 

 found in moist brain-substance in three such experiments. The 

 results are also given, calculated upon the quantity of solid 

 matter in the brain, as found by drying to constant weight at 

 100°C. The fallacy in drying lipoid-containing substance in the 

 air at 100°C. will be obvious, but the results are given thus, 

 pending a better meaning of the term " total solids." 



The brain-pulp gave, as average of four estimations, 78*07 % 

 moisture, or 21-93% total solid matter. 



ii. The Nature of the Fatty Acids op the Brain. 



■ Method of obtaining the fatty acids. 



The brain-substance was saponified in small lots (three), with 

 potash, the whole operation being conducted in an atmosphere of 

 coal-gas; the saponified mixture was then poured into a large 

 flask and treated with excess of H.,SOi(20%), or HC1(1 in 4), 

 freed from oxygen (by cooling in a stream of coal-gas), ether was 

 added, and the whole transferred to a Winchester quart and 

 placed in a shaking machine for one hour; the coloured ethereal 

 layer was separated and concentrated; the concentrated ethereal 

 solution was then resaponified by the method of Kossel and 

 Obermiiller.* This elegant method is well adapted to work of 

 this kind. The precipitated soaps were allowed to stand all night, 

 then centrifuged, and washed repeatedly in the centrifuge with 

 ether (five washings) till the ethereal solution was colourless. 



The united sodium-soaps were preserved in dessicators in an 

 atmosphere of GO 3. 



* Kossel & Obermuller, H. S. Zeit. phys. Ch., Bd.xiv. 599(1890). 



