es which either kill the germ or rob it of its power for harm;
but these properties suffice only when the general health is unimpaired.

In case the attack is not successfully repelled at the outset, what
happens? There begins a struggle between the invaders and what may be
called the reserves of the organism, consisting of the white blood
corpuscles, which undergo a great augmentation in number. These
corpuscles are endowed with the faculty of amoeboid movement; that is to
say, they may shoot out projections from their substance, and even
convert themselves for the time being into traps, seizing upon the
pathogenic bacteria, incarcerating them within their own mass, and
carrying them away to be thrust out of the system by organs whose
function it is to eliminate extraneous matter. These corpuscles are,
indeed, said figuratively to _eat_ the malign micro-organisms, whence
they have been termed phagocytes (from [Greek: phagein], to eat, and
[Greek: kutos], a cell); also because they carry away refuse and
noxious material, they have been called "the scavengers of the system."
By means of their amoeboid movement they are enabled to worm themselves
through inconceivably minute apertures in the blood vessels, and attack
and devour peccant matter wherever it may have effected a lodgment.
These white corpuscles are also known as leucocytes, and their increase
in number when they are called upon to resist bacterial invasion is
spoken of as hyperleucocytosis. The discovery of their protective
function is to be credited to Metchnikoff, a Russian physician now
teaching in Paris. When they migrate from the blood vessels in great
numbers they finally, after having fulfilled their office as phagocytes,
degenerate into the corpuscular elements of pus, which is the creamy
liquid contained in an abscess. Their migratory power was discovered
by Cohnheim.

But as a general thing the phagocytes do not succeed in making away with
all the pathogenic germs, or even with enough of them to prevent the
illness which they tend to produce. The further combat is between the
poisonous products, termed toxines, engendered by the bacteria and
certain antidotal substances, called antitoxines, newly created in the
watery portion of the blood by some wonderful provision of Nature that
is not yet well understood. Each infective disease has its special
toxine, and for the destruction of each the blood prepares its
particular antitoxine; possibly, however,