The army of defense is made up of the white blood corpuscles or leukocytes and of connective tissue cells which separate themselves from the neighboring tissues.  All these wandering cells possess the faculty of absorbing and digesting microbes.  They contain certain proteolytic or protein-splitting ferments, by means of which they decompose and digest poisons and hostile microorganisms.  On account of their activity as germ destroyers, these cells have been called germ killers or phagocytes.  In their movements and actions these valiant little warriors act very much like intelligent beings, animated by the qualities of patience, perseverance, courage, foresight and self-sacrifice.

The phagocytes absorb morbid matter, poisons or microorganisms by enveloping them with their own bodies.  It is a hand-to-hand fight, and many of the brave little soldiers are destroyed by the poisons and bacteria which they attack and swallow.  What we call pus is made up of the bodies of live and dead phagocytes, disease taints and germs, blood serum, broken-down tissues and cells, in short, the debris of the battlefield.

We can now understand how the processes just described produce the well-known cardinal symptoms of inflammation and fever; the redness, heat and swelling due to increased blood pressure, congestion and the accumulation of exudates; the pain due to irritation and to pressure on the nerves.  We can also realize how impaired nutrition and the obstruction and destruction in the affected parts and organs will interfere with and inhibit functional activity.

The organism has still other ways and means of defending itself.  At the time of bacterial infection, certain germ-killing substances are developed in the blood serum.  Science has named these defensive proteins alexins. It has also been found that the phagocyte and tissue cells in the neighborhood of the area of irritation produce antipoisons or natural antitoxins, which neutralize the bacterial poisons and kill the microorganisms of disease.

With the Evil, Nature Provides the Cure

Furthermore, the growth and development of bacteria and parasites is inhibited and finally arrested by their own waste products.  We have an example of this in the yeast germ, which thrives and multiplies in the presence of sugar in solution.  Living on and digesting the sugar, it decomposes the sugar molecules into alcohol and carbonic acid.  As the alcohol increases during the process of fermentation, it gradually arrests the development and activity of the yeast cells.

Similar phenomena accompany the activity of disease germs and parasites.  They produce certain waste products which gradually inhibit their own growth and increase.  The vaccines, serums and antitoxins of medical science are prepared from these bacterial excrements and from extracts made of the bodies of bacteria.