Reserve ambulances can be called upon in case of need. As soon as operated upon, and out of immediate danger, the wounded, in the majority of cases, can be evacuated to permanent hospitals further back in the rear. In case of retreat, the formation, if warned in time, falls back carrying with it if possible all the wounded and follows the troops. These tent hospitals carry with them the wherewithal to instal an operating theatre and a _section d’hospitalisation_, composed of a hundred beds, five double-walled tents, and the necessary doctors and male attendants. Of course the problem of removing the wounded from these tent hospitals at the Front is always a grave one. When the war took on the character of a siege war, a train acted as a sort of shuttle from the field ambulances to the station where the "army zone" finished and the "interior zone" began. The two were generally seventy or eighty miles apart. Here the wounded were carried to the other train, where the cases were sorted out and sent to the distant base hospitals. But, as I have said, the tendency was to keep the slight cases as near as possible to the lines, and send only to distant parts either medical cases—infectious diseases, and convalescents—or the more serious surgical cases, which were entering upon a secondary phase. One of the most interesting aspects of the question of the treatment and recovery of the wounded was the utilisation of the mineral waters which exist in such abundance in France, particularly in the Pyrenees; and all the well-known stations of this delightful region were filled with soldiers recovering from their wounds or illnesses incurred in the service of the country. Magnificent results were obtained also by the same means in ’70. Strongly impregnated sulphur waters gave then, as they have given during this second war, most admirable results, particularly in combating the infection of wounds caused by fire-arms. It is not necessary to insist upon the dreadful error of the theory that bullet wounds were clean wounds. Before it was discovered that the bullet infected the surrounding tissue much harm had been done. The mineral waters were also invaluable in the treatment of nervous affections arising from wounds and rheumatism contracted in the trenches. Some really remarkable recoveries have been made in this glorious region irradiated by the sun and full of pure air charged with the balsamic odours of a pine-clad district.