We have been fortunate, in this issue, in finding three such experts on the subject of the sledge dog and dog-driving as Captain Helmer Hanssen, Dr Seymour Hadwen, and Mr Andrew Croft, willing to contribute their views on the subject. The first on the list, Captain Helmer Hanssen, needs no introduction; he will be remembered as one of Amundsen's companions on his South Polar journey, and on the North West Passage Expedition on board the Gjoa. Dr Hadwen, the second on the list, has gone deeply into the matter both from the point of view of a veterinary surgeon, and of a lover of the animals, and a dog-driver. He has incorporated in his article the results of practical experience in Alaska, as well as more academic work in the Eastern Arctic. Mr Croft spent a winter in Western Greenland, prior to Martin Lindsay's expedition, learning dog-driving from the best exponents of the art in Greenland. He was in charge of the dogs both on the British Trans-Greenland expedition, 1934, and again in 1935–36, with the Oxford University Arctic expedition in North East Land.