304 PA THOGENIC BA CTERIA.

The strongest serum ever obtained by the author con-
tained 1400 units per cubic centimeter.

As the quantity to be injected at each dose diminishes
according to the number of units per cubic centimeter
the serum contains, it is of the highest importance that
the serums be as strong as possible. Various methods of
concentration have been suggested, such as the partial
evaporation of the serum in vacuo, but none have
proved satisfactory. The latest suggestion comes from
Bujwid,1 who finds that when an antitoxic serum is
frozen and then thawed, it separates into two layers,
an upper watery stratum and a lower yellowish one; the
antitoxic value of the yellowish layer is about three
times that of the original serum.

Ehrlich asserts that 500 units are valueless: 2000 units
are probably an average dose, and, as the remedy seems
harmless, it is better to err on the side of too much than
on that of too little. Fourteen thousand units have been
administered in one case with beneficial results.

The largest collection of statistics upon the results of
antitoxic treatment in diphtheria in the hospitals of the
world are probably those collected by Prof. Welch, who,
excluding every possible error in the calculations, u shows
an apparent reduction of case-mortality of 55.8 per cent."
One of the most important things in the treatment is
to begin it early enough. Welch's statistics show that
1115 cases of diphtheria treated in the first three days
of the disease yielded a fatality of 8.5 per cent., whereas
546 cases in which the antitoxin was first injected after
the third day of the disease yielded a fatality of 27.8 per
cent.

After the toxin has set up destructive organic lesions'
in various organs and tissues of the body, no amount
of neutralization will restore the integrity of the parts,
so that the antitoxin must fail in these cases.

The urticaria which sometimes follows the injection

1 Centralbl. /. Bakt. ^^,. Parasitenk., Sept., 1897, Bd. xxii., Nos. 10 and II,.
p. 287.