Those ailments which are described by the word sickness, joined to a prefix, are of two kinds. Either the prefix is the cause of the disease, as in the case of sea sickness, or the expression is a _lucus a non lucendo_, as in the case of 'home sickness,' the cause of the sickness being in the latter case the exact contradictory of the prefix. Sometimes the two kinds are combined, as in the case of love sickness, when both love itself and also the lack of love are the simultaneous cause of the disorder. Mountain sickness, on the other hand, may be of either kind, though not of both at once. I have often had bad mountain sickness of the one kind in the plains of India. Any one who has spent his boyhood scampering over Scotch hills or in similar pastimes is peculiarly prone to this form of the disease towards the end of a hot June. Ten days' leave, or more if possible, is then the only remedy. I had never experienced the other form till I reached Gnatong. I don't exactly know how doctors describe it in diagnosis. I believe, though, that they attribute it in some way to your blood not running up the hill as fast as you do yourself, which results in blood collecting in your toes, which ought to be running about your brain and lungs. Hence giddiness, nausea, headache, loss of appetite, insomnia, difficulty in breathing, and, saddest of all in some cases, an utter inability to enjoy either your drink or your tobacco. I got it badly with all the symptoms, including the last two. I was supposed to be very busy helping to see each column onwards. They were got through without difficulty--no one would stay at Gnatong an hour longer than he could help. So I suppose I performed my share of the work all right, though it was done from bed. There was no one there to supervise my work, and I therefore did not have to go upon the sick list; but even so the feeling of being incapacitated by some accidental ailment at the beginning of an expedition, and of its possibly preventing you from reaching the front, is one of the most trying of ordeals. The number of victims of mountain sickness at Gnatong was considerable. There was an enterprising Parsi merchant who had opened a store there. His wealth of tinned provisions and whiskey lay in the shop comparatively disregarded, but he did a roaring trade in phenacetin and Stearne's headache cure among the mountain sick. Mountain sickness is like measles. If you get a really good go of it, you are not likely to be soon attacked again by it, even though you have to ascend to an altitude far higher than that at which you originally succumbed. Many a man lay gasping for several days at Gnatong, which was only twelve thousand odd feet up, and later on climbed the Karo-Là (16,800 feet) on his own flat feet, smiling.