Each battalion at the front has a headquarters, usually in a dug-out or a sheltered farm house close to the lines: each brigade, consisting of four infantry battalions has a headquarters farther to the rear: each division, consisting of three infantry brigades, artillery, etc. has a divisional headquarters in some town, still farther to the rear, out of shell range: each corps comprising two to four divisions has its headquarters in a town back of this again: each army, composed of two to four corps, has its headquarters still farther to the rear, and the popular idea of the Tommy is that since the respective headquarters occupy bigger and bigger chateaux the farther back they go, away back somewhere in a town all by himself, living in a big castle from which he operates everything, is the commander-in-chief of the whole British Army. General headquarters is usually a very busy place, for there are the heads of the various services of the army, and all the orders affecting the army as a whole are issued through it. The offices of the chiefs of the services are business offices and are operated in a most business-like way. The system is so perfect that it is difficult to escape from it should an order be neglected or a duty left undone. Among these chiefs is the Director-General of Medical Services of the British Army in the field, General Sir Arthur Sloggett. Through him and his deputy, General Macpherson, went all the general orders affecting the health of the army. At the head of each army medical service is a Surgeon-General (D.M.S., or Director of Medical Services), and at the head of each corps a full colonel (D.D.M.S. or Deputy Director of Medical Service). The chief medical man of each division is also a full colonel (the A.D.M.S. or Assistant Director of Medical Services), and he is responsible for the operation of the field ambulances and the evacuation of the wounded to the casualty clearing station while his division is in the firing line. The medical officers of battalions and the sanitary squad are also under him. The casualty clearing stations and the mobile laboratories, are under the D.M.S. of the army, who is responsible for the clearing of the hospitals by motor ambulance convoys and by hospital train. There are normally three field ambulances to each division and one casualty clearing station. The number of base hospitals to each division is normally two, but as many of these are utilized as are needed. They are scores of miles from the fighting zone, and do not particularly concern us here.