For the correctness of this definition there is an infallible test. If after that which we have designated as morbid matter has in a suitable manner been removed from the system, the disease itself disappears, and the body at the same time regains its normal form, the truth of our definition has been established.

But now let us approach the question as to what may be the nature of this foreign matter, and how it gets into the system.

There are two passages through which matter can be introduced into the body—by the nose into the lungs, and by the mouth into the stomach. Each of these passages is guarded by sentinels, who are not, however, thoroughly incorruptible, and sometimes they let things pass which do not belong to the body. These sentinels are the nose and the tongue—the one for air, and the other for food. As soon as we fail to promptly obey the sense of smell and taste, they grow more lax in the fulfilment of their duty, and gradually allow harmful matter to pass unchallenged into the body. You are aware how one can become used to sitting in dense clouds of tobacco smoke and inhaling it just as if it were healthy fresh air. The tongue has been still further corrupted, and we know that it can gradually be habituated to most unnatural food. Need I remind you of the different dishes and beverages which we now think indispensable, all of which were unknown some centuries ago? To these the present generation has grown so accustomed that it would rather renounce a natural diet than give them up.

Our lung-diet is, on the whole, not so degenerate as our stomach-diet, as the former admits of no luxurious outlay. As a rule, the purest air, even today, still suits us best, whereas a hearty dish of porridge, for example, such as furnished our ancestors with blood and strength, is really relished by very few.

In order to illustrate still more plainly how the digestive organs are slowly undernourished by the unnatural demands put upon them, I will adduce the following example. A dray horse that can draw 50 cwt with ease, may be made temporarily, with the aid of a whip, to drag a much greater load, say 80 cwt. If his master, however, having seen that the horse could draw the 80 cwt, were to give him this load daily, the animal might be able to draw this increased load for a short time, but the over-exertion would soon prove injurious. He would drag the load with increasing difficulty, until finally he could no longer draw even 50 cwt. The animal has been overworked, which would outwardly be apparent from his sprained legs and other symptoms. It is exactly the same with the human organs of digestion. For a very long time they will perform work far exceeding their natural functions, continually spurred on by the stimulants of our times. But their natural powers are gradually undermined and then they can only partially perform the work allotted to them. The transition from health to disease goes on so imperceptibly (often ten or twenty years or more) that the patient does not notice the alteration for a long time.

It is very hard to say what amount of food forms the limit which may be borne by a diseased stomach. Often for instance one apple will benefit a weakly patient, whilst two would be injurious. One apple the debilitated stomach can digest, two would be too much. All excess is poison for the body. We must never forget that everything we put into the stomach has to be digested. Even a healthy stomach can really digest only a certain quantity of food. Anything beyond this is poison for it, and if not excreted goes to form foreign matter in the body. Moderation in eating and drinking is therefore the basis of lasting health.

Now what becomes of such foreign matter? I call it foreign matter because it is foreign to the system. The system attempts to expel it, and this in the ways designed by Nature for the purpose. From the lungs it is again expelled directly by exhalation into the surrounding air. From the stomach, the bowels conduct it to the outside; or it first enters the blood and is then secreted by perspiration, urine, and expired air, that is through the skin, the kidneys, and the lungs.

Thus the system takes care in the most obliging manner that our sins have no evil effect. Of course we must not require too much. If we overburden the system with much secretory work, it becomes unable fully to perform its functions and must find room for the foreign matter in its own interior. But such matter is useless for renewing the waste of the body, and is in fact positively harmful as it impedes the circulation and hence digestion. The foreign matter is gradually deposited in various places, especially in the neighbourhood of the secretory organs, that being the direction it takes.

The beginning once made, the deposits accumulate rapidly, unless the manner of living be at once changed.

Alterations in the form of the body now commence, but are at first visible only to the practiced eye. The body in this state is already diseased, though its disease is chronic, or latent, and unaccompanied by pain. The disease develops so slowly that the person affected does not notice it; only after a considerable period does he become conscious of a disagreeable change in his condition. He no longer has the same appetite, he is incapable of the same amount of physical exertion, he cannot do so much continuous brain work, and so on. His condition is still supportable, so long as the secretory organs continue to perform their work, that is, so long as the bowels, kidneys, and lungs are active and the skin exudes warm perspiration. But whenever these functions relax, he at once feels sadly dissatisfied with his physical condition.

The deposits themselves begin, as we have seen, near the organs of secretion, but soon accumulate in remoter parts, especially in the upper portions of the body. This is most distinctly perceptible in the neck. There in the passageway, the alterations may at once be seen, and at the same time the tension observed when the neck is turned from which we can find out from which side the matter has forced its way up.

Before speaking further of the consequences of the accumulation of this matter, I must remark that nowadays the entire evolution of disease can but rarely be watched from the beginning, for most human beings enter the world laden with morbid matter. This is the reason why hardly any child enjoys immunity from so-called children’s diseases. These are, in reality, a sort of cleansing process, this being the way in which the system endeavours to rid itself of the foreign matter.

The foreign substances which at first are chiefly deposited in the abdomen, finally spread through the whole body and hinder the normal development of the organs.

Even should the organs respond sometimes by increasing in size, they can nevertheless attain to no perfect development, for wherever foreign matter is present, space is lost for nutritive material. Besides, as the circulation also is impeded, the process of alimentation is checked, and the organs become smaller, despite, or rather by reason of, the foreign matter deposited in them.

This matter may for a long time remain perfectly quiescent or chronically latent; but under favourable conditions can also suddenly change in form. This foreign matter consists exclusively of substances which are soluble and decomposable; substances which are subject to disintegration, breaking up to yield new formations under the right conditions; substances which are subject to fermentation.

Now fermentation often really occurs in the body and is of the highest significance.

In all such fermentation microscopic fungi are active, and a striking change takes place in the fermenting matter; it increases markedly in bulk.