body of a human being? The guinea-pig was so tiny and the process of
antitoxin-forming so slow, that we naturally turned to larger animals as
a possible source, and here it was quickly found that not only would the
goat and the horse develop this antidote substance very quickly and in
large amounts, but that a certain amount of it, or a substance acting as
an antitoxin, was present in their blood to begin with. Of the two, the
horse was found to give both the stronger antitoxin and the larger
amounts of it, so that he is now exclusively used for its production.

After his resisting power had been raised to the highest possible pitch
by successive injections of increasing doses of the toxin, and his serum
(the watery part of the blood which contains the healing body) had been
used hundreds and hundreds of times to save the lives of
diphtheria-stricken guinea-pigs, and had been shown over and over again
to be not merely magically curative but absolutely harmless, it was
tried with fear and trembling upon a gasping, struggling, suffocating
child, as a last possible resort to save a life otherwise hopelessly
doomed. Who could tell whether the "heal-serum," as the Germans call it,
would act in a human being as it had upon all the other animals? In
agonies of suspense, vibrating between hope and dread, doctors and
parents hung over the couch. What was their delight, within a few hours,
to see the muscles of the little one begin to relax, the fatal blueness
of its lips to diminish, and its breathing become easier. In a few hours
more the color had returned to the ashen face and it was breathing
quietly. Then it began to cough and to bring up pieces of the loosened
membrane that had been strangling it. Another dose was eagerly injected,
and within twenty-four hours the child was sleeping peacefully--out of
danger. And the most priceless and marvelous life-saving weapon of the
century had been placed in the hand of the physician.

Of course there were many disappointments and failures in the earlier
cases. Our first antitoxins were too weak and too variable. We were
afraid to use them in sufficient doses. Often their injection would not
be consented to until the case had become hopeless. But courage and
industry have conquered these difficulties one after another, until now
the fact that the prompt and intelligent use of antitoxin will effect a
cure of from ninety to ninety-five per cent of all cases of diphtheria
is as thorou