Because the life is in the blood, this precious fluid must be protected at all costs. The measures adopted by the body to ward off attack often work on the principle that prevention is better than cure, that it is preferable to keep bacteria out of the body than to fight them within. But what happens once the citadel is breached ?

The body has many features in common with a mediaeval city under siege. The skin is the wall acting as a protective rampart. Picture the city attacked by enemy forces from without. Inside, the citizens are prepared, armed to the teeth. Barriers are to hand to seal off the streets which lead deep into the heart of the city. Building material is stacked at strategic points to thrust into any breach which may occur. Outside, the battering ram hammers at the gates ; miners dig under the wall ; missiles hurtle through the air, seeking entry through some flaw in the defence. On the wall, lookouts report where the enemy activity is fiercest; the city governor concentrates his men in those places ready for any breakthrough. And when a breach is made, thousands of the citizens rush to confine the attackers within narrow bounds, some fighting them hand to hand, others barricading the streets leading off, still others trying to repair the damage even while the battle rages. Deep in the city, the tempo of things is stepped up by the over-ruling power : the smiths work furiously to beat out more swords and spears ; the fletcher feathers countless arrows ; the women prepare food and drink to encourage the weary ; others take up the corpses, and tend the wounded.

While the city works as a whole under the direction of a guiding mind, there is hope that the attackers may be driven off. But once let irresponsible elements refuse to co-operate, and all is lost.

The city must be whole. So must it be with the body. Some of the most curious and disturbing ailments are those which come upon people, whose several parts are not co-ordinated by a united guiding force. The apostle Paul said truly, "Now are they many members, but one body . . . God hath tempered the body together . . . that there should be no schism in the body, but that the members should have the same care one for another’.

What happens then when the citadel of the body is breached ? A simple cut, for example, breaks through the protective skin, and the fine network of lymph vessels and capillaries is fractured : blood oozes out, bacteria move in. If the bacteria once establish themselves in the bloodstream, invasion of the body is much simplified and the invaders will be more difficult to destroy.

Immediately the flesh is cut, a message flashes to the controlling centre, and means are set in motion to seal the wound. There is a two-fold purpose in this ; to stem the loss of life-bearing blood, and to prevent further ingress of dirt and bacteria. The mind does not have to think out a plan of campaign or devise mechanisms to defeat the invaders. These things have already been done by the Master Mind of the Creator. There is no waste of time, no fatal delay ; the reaction is immediate, the means are at the ready.

Patrolling the bloodstream are innumerable workers and warriors, prepared for split-second action, prepared to die for the body they serve. The first task is to conserve the life by sealing the wound. This is the duty of microscopic bodies called platelets which cause the plasma (the liquid part of the blood) in the vicinity of a wound to clot and form a jelly-like plug of thrombo-plastin—a very effective seal. But its very effectiveness could prove disastrous if there were no other means of defence. Quite likely the tool or weapon carries bacteria deep into the wound. What happens now ? The enemy is sealed into an ideal environment; warmth, moisture, darkness are ideal for the rapid reproduction of bacteria. Soon, very soon, millions could be available to penetrate the pulsating channels of the red river of life. But the body is aware of the danger. No ! that is untrue. The body behaves as though it is aware of the danger ; it acts as though a definite purpose is in view, as though it knows the end to be striven for.

Even while platelets and plasma co-operate to plug the wound, other cells are hastening to the scene. Not only must the escape of blood be stemmed, but the infected area must be sealed off to prevent an internal break-through into the main channels of communication. How like human warfare ! The confining of the breach and the guarding of the ways prevent the enemy from enlarging his foothold ; close the lines of communication, and  all will be well. The invading bacteria are cut off behind by the sealing of their way of entry ; they must go forward or perish. The defences of the body are determined that they shall perish. The minute tubes, the capillaries, which feed the area have already constricted, so reducing the flow of blood to make it easier for the plug to be fixed. Now the many cells surrounding the wound start to swell to help close the lymph passages. The blood supply to the area increases, carrying with it millions of warriors prepared for death : these are the white corpuscles, the phagocytes, which attack the bacteria by enclosing and killing them, themselves dying in the process. The platelets extend their sphere of operation around the wound, transforming plasma into jelly, thus impeding bacterial movement, and the whole area is surrounded by fibrous connective tissue. When the seat of infection is effectively sealed off, further chemical changes occur  which break down the skin and allow the dead contestants and the surrounding fluids to be expelled as pus. Should the area near the access point fail to hold the invasion, other adjacent areas will put up inflammation barriers.

If this defence mechanism were absent, a boil would be as dangerous as polio. If there were no defences at all against bacterial invasion, a boil would be as lethal as the headsman's axe.

Occasions arise when the blood does become invaded by bacteria. Further defences are then called into play. The phagocytes occur in their millions throughout the tissues, they wander along the arteries and veins, sometimes against the stream ; they frequent the capillaries and lymph nodes, they line the blood channels of liver and spleen waiting to pounce upon bacteria that try to pass. Wherever they meet a bacterium it is ingested and destroyed, and another marvellous system disposes of the resulting corpses. The lymph nodes and the network of vessels radiating therefrom are profusely distributed in all parts of the body, especially in those places where entrance is most easily effected, such as throat and intestines. These nodes are filled with large phagocytes, eager to repel any attack. So busy may they become that the node painfully swells.

While all these 'hand to hand' combats are in progress, the controlling power busies itself with the body as a whole. Chemicals, notably adrenalin, are poured into the bloodstream to help increase the tempo of all the bodily processes. Temperature rises to fever heat, the heart beats faster thus increasing the speed with which reinforcements (phagocytes) can be hastened to the danger zones, and increasing the rate at which poisons are eliminated. The actual production of red and white blood cells is speeded up to provide replacements for the casualties. The increased temperature of the blood helps to weaken the bacteria.

Over and above all this, in many infections there comes into play "one of the most extraordinary and beautiful processes of natural defence in the organic world." The body reacts to the presence of foreign bodies or chemicals in the blood by the production of antibodies or antitoxins which wage warfare on the invaders. There are various types of antibody : some work hand-in-glove with the phagocytes by altering the bacteria so that the phagocytes can deal with them more effectively ; others cause the bacteria to agglutinate or cling together in masses thus reducing their effectiveness and making them easy prey for the white warriors of the blood and the filters which stand sentinel. Some dissolve the bacteria ; some disable them so that another substance occurring naturally in the blood, can give them the coup de grace ; some prevent the bacteria from multiplying. The antitoxins do not usually attack the bacteria, they are concerned with neutralising the poisons which some bacteria pour into the blood.

Both antibodies and antitoxins are highly specific and will effectively deal with only one kind of infection. Sometimes they remain in the bloodstream after an attack for the rest of the lifetime ; and so effective are they that a second attempt at invasion by the same sort of bacteria has no hope of success.

Such then are some of the wonderful automatic defences to be found in the human body, which obviously (yes ! why should not we be as dogmatic as the rationalists ?) have been designed for the very purpose of protecting the red river of life from contamination.

Another equally extraordinary series of devices comes into play to prevent excessive loss of blood from a severe wound. When such an emergency arises it is vital that immediate action is taken to counter it. How important this is can be better realised when we learn that if the effective blood supply to the brain and heart falls below a certain minimum for more than five to ten minutes, serious and permanent changes may occur in the cells of those organs, resulting in insanity or chronic heart trouble.

Before a first-aider has time to feel in his pocket for means to improvise a tourniquet, the body's defences have leapt into action. The injured blood vessels contract locally, and the platelets and plasma begin the difficult task of attaching thromboplastin jelly to the sides of the wound. It is rather reminiscent of hordes of workmen throwing bags of sand and cement into a breach in a river bank through which water is pouring. It is obvious that more drastic measures will be needed to stem the

escape of life. Rapid loss of a third of the blood from the system will cause death. As the danger level is approached, extra emergency measures are brought into play. The greater the amount of blood lost, the more readily that which remains is able to coagulate, until the stage is reached when clotting is practically instantaneous This remarkable and almost miraculous effect is believed to be due to the action of adrenalin releasing a powerful coagulant from the liver, although in the absence of adrenalin there is still some increase in the speed of clotting.

This is not the only extraordinary reaction of the body to preserve sufficient blood for the life of the creature to continue. There is a contraction of the vascular2 system to the lower volume of the remaining blood so that it remains filled. This contraction is highly selective : the parts feeding those organs which will suffer permanent damage if their supply of blood is much lowered—the brain, heart, diaphragm etc.—do not change. Chance can get no foothold here.

Then there are the reserves held in the spleen, a reservoir of enriched blood containing more than the usual number of red cells : as bleeding progresses, so the spleen contracts and forces this rich blood into the system to help make good the loss. In extreme cases the spleen may contract to a fifth of its normal size. And when the breach is sealed and the centres of life made safe, other structures and devices begin working overtime to bring the volume of the blood back to normal, and to effect permanent repair of the damaged tissue.

All these fully automatic reactions are triggered off by the sensitive nerve ends in the carotid sinus, situated in the neck near the base of the skull. These nerve ends are highly responsive to slight but sudden change in the blood pressure.

When we are confronted by facts such as these, we have to perform mental acrobatics to imagine that they could have arisen by chance. To let such imagination petrify into belief, one has resolutely to depose reason from its prime place in the mind, and set up magic on its throne. Logic becomes a figment, chance a solid reality.

Like all living irrational things, the body structures shout praise for the Mind which designed them and which sustains them in being. Those that we have described are but few among the many. Everywhere we look we can find that a Master Mind has been there before us. Truly we are "fearfully and wonderfully made”.

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