C. I begin to see that I should have been in equally good trim for boating upon a very different kind of breakfast—that what I wanted was fuel for force-making rather than food for muscle-making; and now that I call to mind many facts which have been brought under my notice in countries where olive-oil is a staple article of food, I can, after what you have said about the connection of electricity with muscular action, understand how a man whose food is chiefly polenta or potato, with a little bread and oil, should have had as much muscular power at his disposal as ever I could contrive to compass. I once made the ascent of Etna with two Sicilian guides, who scarcely ever tasted any animal food except a morsel of fat bacon, and who lived chiefly on polenta and bread and olive-oil. More than once I thought I should never get to the top; they trudged upward with scarcely a sign of distress, though often having to expend a good deal of strength in pushing or pulling me up. And yet I was in what I thought to be an excellent "condition" at the time.
C. It is, I suppose, right to believe that most of the weaklings who are benefited in this country by cod-liver oil, in Switzerland by neat's-foot oil, and in Russia by train-oil, would never have required these oils as medicine if their food had been sufficiently rich in fatty and oily articles. Cod-liver oil, I have heard you say again and again, has no special virtue of its own; it does good simply because it is oil. In my parish, where cod-liver oil is now used, suet diffused in milk, by boiling the two together, was used formerly, and, I am told, with equal benefit. In the cases where cod-liver oil is wanted the food in all probability has been lacking in fatty or oily matter. More force fuel was wanted, I suppose.
M. I have a notion that the beneficial action of the fats and oils is not wholly to be accounted for by regarding them merely as force producers. I believe that they actually serve as food for nerve-tissue. This tissue is in the main made up of a peculiar kind of fat, and I am convinced that nerve is starved if the food be wanting in a sufficient quantity of fatty or oily matter. I find that very many persons suffering from various chronic disorders of the nervous system have abstained from the fatty and oily articles of food, and that their state is almost invariably very much changed for the better when you can get them to take what they have avoided; I also find that a great number of delicate infants who can not take skimmed milk, and who do not take kindly to unskimmed milk, will take milk without any difficulty when it is enriched with cream. You may say if you will, "These facts only show that the fatty and oily matters have done good in these cases by acting as force-fuel," and I do not care to contradict you flatly. Indeed, all I can say is that I do not think I am illogical in supposing that they may do good also in serving as food for nerve tissue.