Lipid Metabolism in Brain during Myelination”

In the preceding invest,igations (1, 2) the rate of turnover of lipids was found to be slower in the brain of adult rats than in other organs (liver and intestine) studied for comparison. In this investigation lipid metabolism was studied during the time of its greatest activity in nervous tissue-the period known to morphologists as that of myelination. The process of myelination has been little studied from the biochemical point of view since the classical investigation of Koch and Koch (3) on rat brain. Indeed t.he only studies of brain lipids during the period when myelination takes place, aside from that of Koch and Koch, appear to be a few analyses of formalinfixed tissue by Smith and Mair in puppies (4) and in man (5), determinations in three infants by MacArthur and Doisy (6), and some analyses of phospholipid by McConnell and Sinclair (7). Koch and Koch found a rapid increase, both relative and absollltc, of phosphatide between the 10th and 20th day of extrarlterinc lift. l?rom the 20th day on the percentage remained constant, though there was a gradual increase in the absolute amount with growth of the brain. Cerebrosides doubled in percentage amount between the 20th and 40th day. The percentage of cholesterol fluctuated widely and the data are of little value as the determinations were made by difference. The findings were correlated with the process of myelination which from