Vilhjalmur Stefansson has had the extraordinary privilege and the rare merit to know intimately certain segments of the world which will always be strange to most of us. He has had the alertness to note details, to make correlations which would have escaped others. He has been unhampered by professional or even by lay prejudices. And he has a gift for expressing the ideas which his observations have evoked.The story which he presents in this book is a fascinating one. Here is the sort of thing we call basic research, just as much so as if it were being conducted in the latest of laboratories. Here are the data from a series of experiments which Nature has performed for us-in the Arctic northland, in the tropic forests of Gabon, and in the temperate valley of Hunzaland. She has varied a series of environmental factors yet come up with a like result in the three places, and a result which she has produced, so far as we know, only in those three special combinations of environments, not in any other of her myriads of combinations elsewhere. What have these three in common, that they produce this result, so important to us? Nature will not repeat those experiments. And we will not have another Stefansson to read the data and present them to us. I hope, therefore, that what he has to say will be read carefully and pondered deeply.