powerful weapon and each will always cause casualties, but proper discipline and protective masures will greatly reduce the number of these casualties, and particularly so with regard

to gas.

f. Chemical warfare intelligence-Chemical warfare inteliigence is a separate subject in itself, but certain phases of it are so closely related to defense against chemical warfare that they must be mentioned briefly here. The regimental, battalion, and separate unit staff officers and chemical warfare officers must constantly be on the lookout for any new developments in chemical warfare by the enemy, including both chemical agents and methods of projection. They will make every effort to obtain samples of these new developments and transmit them to higher authority for examination and study. Such samples should include samples of earth soaked with a new chemical agent," duds" or captured shells, captured weapons, etc. This work is important, for obviously if our protective measures are to he kept up to the highest state of efficiency, it can only be done by keeping accurately posted on all new problems as they arise,

361. Chemical agents-a. Definition.-The term chemical agent includes those chemicals and chemical compounds, whether gases, liquids, or solids, used in chemical warfare. Chemical agents differ materially from other weapons used against an enemy. They are independent of momentum or disruptive forces, and depend only on direct chemical action for effect.

b. Classification. The several chemical agents fall under different classifications, based upon their

(1) Physioul state-This classification is based upon the physical condition at ordinary temperatures likely to be encountered under field conditions. Thus the agent may exist as a gas, liquid, or solid.

(5) Physiological action.This action of chemical agents tends to be specific in the sense that their actions are limited to particular parts of the body. As a result, they are grouped into close necording to their physiological effect on the human

+1 use--Chemical material may be a noxious gas, diary material. Noxious gases are used to dis1. reduce their fighting efficiency, or interdict to blind hostile observation or screen the moveown troops; incendiary material to disable perTroy material,

362. Offense methods and principles.-The tactical use of gas is discussed in Field Service Regulations, and will be covered in detail in the various Training Regulations.

363. The gas mask.-a. Types.-The gas mask is the fundamental apparatus for individual protection. There are three types of masks now in use by the Army, viz: The A. T. (Akron Tissot); the K. T. (Kops-Tissot); and the Model of 1919. These types differ only in structural details, each being an improvement over the preceding one. The Model of 1919, together with the diaphragm mask recently adopted, is the standard for future manufacture and issue to the Army, and the A. T. and K. T. types will continue to be used for training and emergency purposes so long as usable or until there are a sufficient number of standard types to supersede them. A description of the gas mask and its carrier is contained in Technical Regulations No. 1155-5.

b. Protection afforded by the gas mask.-The gas mask gives practically perfect protection against all chemical agents which attack the lungs and eyes. It also mechanically protects that part of the face which it covers. Obviously, it does not furnish protection to the body from chemical agents of the mustard type.

c. Extra canisters.-Extra canisters are provided for use in the field, but are not issued with the original mask. The life of canisters in the field is normally much shorter than that of other parts of the mask.

364. The gas chamber.-a. Appearances and general use.-The gas chamber is simply a room or other inclosed space which is filled with a concentration of a chemical agent approximately equal to that likely to be encountered in the field. The gas chamber serves two purposes: To test the fit of the mask to the face by exposing men to a lachrymator while wearing the mask, and to give practice in mask adjustment under simulated field conditions by requiring the men to enter a concentration of toxic gas without wearing the mask and to put it on in the toxic atmosphere. Exposure to toxic gas while wearing the mask tends also to give the wearer confidence in the protective ability of the mask.

365. Matériel for collective protection.-This includes gasproof shelters, alarm devices, chemicals for destroying chemical agents, mobile bathing units, and protective covers or containers for matériel.

366. Gas-proof shelters.-a. Uses.-A gas-proof shelter in any inclosed space which has been constructed so that gas can not

enter it. A gas-proof shelter may or may not be bomb proof. it may be a dugout, a hut, or even a tent if specially built with this idea in view. Gas-proof shelters are a very useful form of collective protection. They provide places where men who have to work for long periods of time in a gassed area can come, take off their masks, and rest. They provide places where men who are wounded in a gassed area and who can not wear the mask can be placed pending evacuation. Most important of all, they enable medical dressing stations, telephone centrals and signal stations, observation posts, headquarters, and other activities whose efficiency would be considerably reduced by the wearing of the mask to function without interruption during a gas attack.

367. Alarm devices.-There are two types of alarms to be given in case of an enemy gas attack: General alarms and local alarms. General alarms are given only in the case of cloud-gas attacks of considerable magnitude which are expected to involve a large area. Local alarms are given in all other cases. General alarms are sent out by means of all normal methods of communication such as the telephone, radio, etc. Local alarms are sent out in the same manner when necessary, but additional special-alarm devices are also provided. These special devices all depend on the production of sound as a means of giving the alarm. The most widely used of these devices is the Klaxon horn. Iron triangles, empty shell cases, and watchmen's rattles have also been used. These alarms may be installed in appropriate places or carried by gas sentries.

368. Protective covers and containers for matériel.-Most chemical agents have a corrosive action on metals. The mustard type has no corrosive action, but its presence on matériel is highly objectionable, owing to the danger of infecting those who handle and use the matériel. Chemical agents also render food unfit for use, and the mustard and toxic smoke types render water unfit for drinking. Protection of all metallic matériel and food from chemical agents is therefore most important. If available, the gas-proof shelter offers the best solution of the problem, but in its absence the use of boxes or other containers lined or covered with tar paper or oilcloth will serve the purpose. In an emergency, the matériel or food may be simply wrapped in tar paper or oilcloth.

369. Protection against smokes and incendiaries.-No apparatus is provided for protection against incendiaries. The gas mask protects the eyes and lungs from smoke fumes.

370. Scope of training in individual protection.-Training in individual protection should consist of the following:

a. Use of the mask (mask drill).

b. Inspection and care of mask.

c. Mask drill practice in gas (gas chamber).

d. Wearing of mask during all the various military operations. e. Adjustment of the horse mask.

f. Practice in identifying chemical agents by odor.

371. Mask drill.-a. General.-Preliminary drill will be by the numbers in order to obtain complete and accurate adjustment of the mask. Proficiency in this drill will be followed by practice without the numbers to insure as quick an adjustment as possible, and practice in holding the breath will be included. As a rule, careful adjustment is more essential than great speed.

The headpiece may be worn with the strap adjusted either under the chin or at the back of the head. A change in the drill is necessary, depending upon the method used.

b. Mask drill-Side satchel The modern or 1919 model. (1) Drill A-To sling the mask.-1. Sling, 2. MASK. Grasp the metal hook above the two snap fasteners with the left hand, at the same time grasping the metal clasp at the extremity of the shoulder sling with the right hand. Hold the mask waist high in front of the body with side containing snap fasteners next to the body. (Two) Extend the left arm sideways to full length. At the same time pass the shoulder sling over the right shoulder with the right hand, then bring the two hands together across the chest and fasten the hook and clasp together. Adjust the satchel in its proper position under the left arm. Pass the waist strap around the waist and fasten together in front.

(2) Drill B--Drill by numbers to obtain accurate adjustment of the face piece.-(a) First method. The headpiece adjusted with strap under the chin. 1. By the numbers, 2. GAS. Stop breathing. Place rifle (if unslung) between knees; with left hand open flap; with the right hand knock off headpiece from behind, and, going on down with the same movement, bring the right arm in front of the body, keeping the forearm at right angles to the upper arm, until the hand is on a level with the opening of the satchel, Thrust the right hand into the satchel, grasping face piece between the thumb and fingers just above the angle tube. (Two) Bring face piece smartly out of satchel to height of chin, holding it firmly in

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both hands with the fingers extended and joined outside of the face piece, the thumbs inside at the binding midway between the two lower straps of the head harness. Thrust out the chin. (Three) Bring the face piece forward, digging the chin into it. With same motion guide straps of the harness over the head with the thumbs. (Four) Feel around the edge to make sure the face piece is well seated. See that head harness is corectly adjusted. (Five) Close outlet valve by pinching between thumb and fingers of right hand to prevent passage of air through it and blow vigorously into the mask, completely emptying the lungs. (Six) Replace headpiece. Pass the flap of the satchel around the corrugated tube and fasten on the outer snap fastener.

(b) Second method. The headpiece adjusted with strap at the back of the head. 1. By the numbers, 2. Gas. Stop breathing. Place rifle (if unslung) between knees. With left hand open flap, at the same time holding the right arm with forearm across the front of the body, the forearm at right angles to the upper arm and at the same level as the opening of the satchel. Thrust the right hand into the satchel, grasping face piece between the thumb and fingers just above the angle tube. (Two) Bring face piece smartly out of satchel to height of chin, holding it firmly in both hands with the fingers extended and joined outside of the face piece, the thumbs inside at the binding, midway between the two lower straps of the head harness. Thrust out the chin. (Three) Bring face piece forward, digging the chin into it. With same motion guide straps of the harness over the head with the thumbs, knocking the headpiece off backward. (Four) Feel around the edge to make sure the face piece is well seated. See that head harness is correctly adjusted. (Five) Close outlet valve by pinching between thumb and fingers of right hand to prevent the passage of air through it, and blow vigorously into the mask, completely emptying the lungs. (Six) Replace headpiece. Pass the flap of the satchel around the corrugated tube and fasten on the outer snap fastener.

(3) Drill C-Method of testing for presence of gas.-Mask being adjusted: TEST FOR GAS. Take a moderately full breath. Stoop down so as to bring the face close to the ground but do not kneel. Insert two fingers of right hand under face piece at right cheek. Pull the face piece slightly away from right cheek and sniff gently. If gas is smelled, readjust the face piece. Close outlet valve by pinching between thumb and