Pathogenic Bacteria

IMMUNITY AND SUSCEPTIBILITY. 73

It need scarcely be pointed out that a loophole of doubt
•exists in all these illustrations: the bacteria may have been
dead before the cells ingested them, and the phenomena of
digestion and destruction which have gone on in their in-
teriors may have been exerted upon dead bacteria. To the
relapsing-fever illustration we may take exceptions, and
state that the apyrexia may have marked the death of
the spirilla, which were taken up by the leucocytes only
when dead. In the erysipelas illustration the streptococci
remote from the centre of the lesion may have met from
the body-juices or some other cause a more speedy death
than that from the digestive juices of the leucocyte.

Metsclmikoff, however, is prepared to show us that the
leucocytes do take up living pathogenic organisms. He
.succeeded in isolating two leucocytes, each containing an
anthrax spore, and conveying them to artificial culture-
media, where he watched them. The new environment
being better adapted to the growth of the spore than for
the nourishment of the leucocyte, the latter died, and
the spore developed under his eyes into a healthy bacillus.
Seeing that the animal cells take up bacteria, and seeing
that the ameba can ingest and digest u threads of lepto-
thrix ten times as long as itself," we need only put two
and two together to see that MetschnikofPs theory rests
upon a very substantial foundation. The more virulent
the bacteria, the less ready the leucocytes are to seize
them. The more immune the animal, the greater is the
affinity of the leucocyte for the bacteria.

The organisms which are seized upon by the leucocytes
do not remain in the blood, but are collected in the spleen
and the lymphatic glands; and not the least important
fact in favor of phagocytosis is that observed by Bardach,
that excision of the spleen diminishes the resistance to
infectious disease.

Quinin also furnishes a therapeutic support to the
theory. It is known that quinin increases the destruc-
tion of leucocytes. Woodhead inoculated a number of
rabbits with anthrax, giving quinin to some of them.