Nineteen-day old female weanling rats were maintained on diets deficient in essential fatty acids, low in zinc (6 p.p.m.) or both deficient in essential fatty acids and low in zinc; the weights of their brains were 25.6, 35.0 and 43.2% respectively, less than those of rats on control diets. 2. In essential fatty acid deficiency, the myelin lipids cerebrosides and sphingomyelin were considerably reduced in proportion whereas zinc deficiency had no significant effect on the proportions of the lipids. 3. Essential fatty acid deficiency was also characterized by the appearance of a high proportion of eicosatrienoic acid (20:3) and the reduction of arachidonic acid (20:4) and the other essential fatty acids. In zinc deficiency, however, there was an accumulation of arachidonic acid. 4. The low-zinc status aggravated essential fatty acid deficiency causing a higher reduction in the proportion of the myelin lipids and the accumulation of both eicosatrienoic and arachidonic acids. 5. It is considered that zinc plays some role in the metabolism of essential fatty acids in brain lipids and the pathological effect of the double deficiency of essential fatty acids and zinc causes a greater impairment to brain development and maturation than either of the single deficiencies.
