I have mentioned the deleterious effect of altitude on the appetite of some of our older members; but the same was to some extent true of us all. I have the most vivid recollection of distaste for food during our first few days at Camp III, and especially of the way one had almost to push a prune down one’s throat on the way up to the North Col; but with the majority of us this distaste for food (especially for meat and the slowly-digested foods) diminished during our sojourn at great heights, though our appetites never became quite normal until we reached one of the lower camps. Those who had oxygen reported that they had large appetites above the North Col; and there is no doubt that it is the rarefaction of the air that causes this alteration of the appetite. One may perhaps be justified in assuming that the secretion of gastric juice is diminished while air that is poor in oxygen is inhaled, though it is rather hard to understand how this is brought about. Although acclimatisation is not entirely connected with the actual increase in the number of blood corpuscles (as has been proved by Barcroft in 1922), yet this is still recognised as one of the important factors in its production. But this increase in the concentration of the blood must be associated with a great increase in its viscosity, and when that is combined with intense cold with its accompanying constriction of all the smaller blood-vessels, there are present all the conditions necessary for the production of frostbite. Therefore acclimatisation with all its benefits probably increases the risk of frostbite; hence one who is acclimatised must be especially careful of feet and hands and their coverings. It is hard to put on too many clothes at a great altitude, and very easy to put on too few.