Although much work has been done on the levels of cholesterol, cholesterol esters, and the various phos-pholipids in the blood and inthe brain of patients with multiple sclerosis, little attention has so far been paid to the nature and proportions of the differ-ent fatty acids presentas cholesterol esters or as components of the different phospholipids. In 1963, however, Baker, Thompson, and Zilkha reported briefly on the fatty acid composition of lecithin fractions extracted from the white matter of six normal brains and of nine brains from patients with multiple sclerosis. The areas of white matter dissected from the brains of patients with multiple sclerosis appeared normal on inspection, and in no case was tissue taken from the immediate vicinity of a recognizable plaque. The findings appeared to indicate a shift towards greater saturation of the fatty acids in this fraction of the white matter in multiple sclerosis, the percentage of palmitic acid being in-creased and those of palmitoleic and arachidonic acids decreased.

Since the publication of these results Gerstl, Tavaststjema, Hayman, Smith, and Eng (1963) have also described a study of the fatty acids in human brains, in which they found that the levels (expressed as m-moles/100 g. wet weight of brain) of both saturated and unsaturated fatty acids in the unfractionated lipids of white matter from one multiple sclerosis brain were slightly lower than the mean levels obtained from three normal brains. In discussing their own findings Bakeret al.(1963) suggested that the changed proportions of fatty acids in brain lecithins in multiple sclerosis could be due to some purely local cause, such as an abnormality of lecithin synthesis or degradation, or could arise as a result of some more general cause, such as a change in the relative amounts of saturated and unsaturated fatty acids reaching the brain. We are therefore now reporting the resultsof a study of the per-centage fatty acid composition of the total lipid extract of serum taken from patients with multiple sclerosis and from control subjects.