"كتيّب الجزيرة العربية. مجلد II. ١٩١٧" [‎٣‎٦‎١] (٥٤٢/٣٦٥)

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HYGIENE AND DISEASE 361
and brewing their distinctive poisons in it. He discovered how to
isolate the germs of this or that disease, and how to grow them in
' pure culture outside the living body, miles away from a patient,
all by themselves, in sterilized broth or on sterilized jelly, in a
flask or a test-tube. From this discovery came the whole series of
discoveries, how to bring down, point by point, the virulence of
a pure culture, and how to render man, or animals, immune against
this or that disease, by treating them with graduated doses of
germs at low virulence, or of dead germs, or of the distinctive
poisons brewed by germs.
For example : sheep and cattle are protected against anthrax by
graduated doses of anthrax-germs at low virulence. Man is pro
tected against typhoid by graduated doses of dead typhoid-germs.
These protective substances go by the name of vaccines, because
of their analogy with ordinary vaccination against small-pox.
Antitoxins differ from vaccines, since animals are used in the
preparation of antitoxins. For example ; diphtheria. If a horse
be treated with graduated doses of the poison brewed by diph
theria-germs in pure culture, the horse becomes in time immune
against diphtheria. Its blood, fighting the poison, the ' toxin
manufactures the ' antitoxin ', the natural antidote to the toxin.
If the serum, the clear part of the blood of this horse, be adminis
tered to a child with diphtheria, it will reinforce the antitoxin
which the child's own blood is manufacturing, and in this way
will help the child to pull through. It can also be used, not only
to cure a child already attacked by diphtheria, but to immunize
a child that has been exposed to diphtheria.
As it is with diphtheria-antitoxin, so it is with tetanus-antitoxin.
The germs of tetanus (lockjaw) live in the surface-soil: in dust,
gravel, earth, and especially in soil heavily manured. If a horse
be gradually immunized against tetanus, its blood is able to im
munize a man, or another horse, against the disease. In places
where the surface-soil is badly infected with tetanus, a man re
ceiving a wound, with particles of mud or earth in it, ought cer
tainly to be thus protected as soon as possible after the injury.
The method is used also to protect valuable horses, either after
a wound or before some operation of veterinary surgery.
These two discoveries of a protective and curative serum for
diphtheria and tetanus have saved thousands of lives. Vaccina
tion against the Enterica bacilli has also proved of great value.
Pasteur's work, also, inspired Lister (1827-1912) to study the
true causes of wound-infection, and to discover the antiseptic
treatment of wounds. Lister's first use of carbolic acid, to