300 



THE FATTY ACIDS OF BRAIN LIPOIDS, I., 



In the preliminary examination of Uie fatty acids the soaps 

 were decomposed in the apparatus pictured below. 



The object of this apparatus is to liberate 

 and wash the fatty acid in an atmosphere 

 of C0„. Tube A is connected to a Kipp 

 apparatus, and B is kept open. 



When the separated fatty acid has risen 

 to the surface, tube B is closed; the force 

 of C0„ then drives the watery solution out 

 at C, which continues to siphon till tube 

 B is opened. The apparatus is heated in 

 a water-bath. The washed fatty acid is 

 then transferred to a weigliing bottle, and 

 dried at 100°C. in a current of anhydrous COo. 



Nature of fatty acids from human brain. 



In a preliminary examination, the lipoids had not been com- 

 pletely decomposed, only a portion of the total fatty acids being 

 split off. For complete splitting up of the lipoids by means of 

 20 % alcoholic KOH, six hours at a boiling temperature is 

 required. An interesting observation was made, however, in 

 that the fatty acids split off most easily from the lipoid bodies 

 have a smaller iodine-absorption figure than those more difficult 

 to split off. 



The mean iodine-value of the total fatty acids from brain was 

 found to be 81-3 % in twelve to fifteen hours, while a sample 

 obtained by incomplete saponification gave a mean absorption of 

 51-3% iodine(Hubl). 



The fatty acids split off at an early stage by incomplete sapon- 

 ification are, when first obtained, pale yellow in colour but 

 gradually darken on keeping, and rapidly at 100°C. ; but when 

 the saponification is continued for six hours, the fatty acids 

 obtained are brown in colour. 



These results poiiit to the conclusion that the lipoids which 

 most resist saponification contain fatty acids of an unsaturated 

 nature. 



