There was a large field open to me. I had retained the knowledge I had acquired as an instructor of recruits. It was not a question of worrying the men with theories, but they willingly collected to have friendly chats, and ended by enjoying the séances, where one evening, after having explained the principles of orientation to them, I taught them how to recognise the Great Bear and the Polar Star. On other days we went into other matters: to do with the advance under fire, of the artillery and infantry (we knew all about that!), of the supply of ammunition and the commissariat; or of subjects vaster still--Germany's ambitions, and the causes of the present war. When we were marching we organised competitions in judging distances. We picked out a tree or a house, and then each one had to calculate how many steps he expected to take, and count them afterwards to see how far out he was. Lamalou proved to be extraordinarily gifted in this respect. He was never more than twenty yards out. We would find a way of making use of that. After a few tentative ventures, I found my bent. I had always been interested in medicine. A handbook on hygiene, which De Valpic lent me, completed my sketchy equipment. The next thing to be done was to put it into practice. The soldiers suffered chiefly, as usual, from sore feet--a crop of blisters and sores. I preached cleanliness first, and methodical greasing. But the sore places, some of which were septic, must be cured. Most of the men seemed entirely ignorant of how to treat a blister. Guillaumin and I arranged a demonstration one evening with great success. Once having won their confidence, we treated them for various little ills--diluted tincture of iodine did wonders. One great danger was the water, which caused a great deal of diarrhoea. It was not always possible to boil the contents of our water-bottles. I had some permanganate of potash; a few crystals placed in the water-buckets assured a relative sterilisation. Our platoon made it a point of honour to have as few men as possible at sick parade. We only had two in a week. Trichet, who sprained his ankle, wept with rage at leaving us. My little cures were appreciated. Men came to ask my advice now, even from No. 1 platoon. I had some idea of massage and set up a surgery. The men appealed to me in doubtful cases. One evening, I remember, the party sent on ahead to choose the camp had picked some mushrooms on the way. Breton insisted on their waiting for me. I really was not very well up in the matter. However, I did not quite like the look of the valvular formation at the base, and ordered them to throw them away. They obeyed without protesting. I learnt shortly afterwards from De Valpic, that it had saved a good many lives.