DIP1I TIIRRL'L 295

bacillus seems to be shorter than the diphtheria bacillus
when grown upon blood-serum; that the cultures in
bouillon seem to progress much more rapidly at a tem-
perature of from 2o°~22° C. than those of the true bacillus;
and that the pseudobacillus is not pathogenic for ani-
mals. These slight distinctions are all exactly what
should be expected of an organism whose virulence had
been lost, and whose vegetative powers had been altered,
by persistent manipulation or by unfavorable surround-
ings.

Park ! carefully studied this subject, and found that
all bacilli with the exact morphology of the diphtheria
bacillus, found in the human throat, are virulent Klebs-
Loffier bacilli, while forms found in the throat closely
resembling them, but more uniform in size and shape,
shorter in length, and of more equal staining properties
with Lofflefs alkaline methylene blue solution, can be,
with reasonable safety, regarded as pseudocliphtheria
bacilli, especially if it be found that they produce an
alkaline rather than an acid reaction by their growth in
bouillon. The pseuclodiphthcria bacilli were found in
about i per cent of throats examined in New York; they
seem to have no relationship to diphtheria. They are
never virulent.

A difference of possibly much greater importance is that
observed by Martini,2 that the diphtheria bacillus will not
grow in fluid antitoxic serum in which the pscudodiph-
theria bacillus thrives. Both the real and the pseudoba-
cilli flourish upon coagulated antitoxic serum. If this dif-
ference in the behavior of the bacilli bears any relation
to the so-called u specific immunity-react ionn of cholera
and typhoid fever, it may he of great future importance.

The diphtheria bacilli are always present in the throats
of patients suffering from diphtheria, and constitute the
element of contagion by being accidentally discharged
by the nose or mouth by coughing, sneezing, vomiting,

1 Scientific Bulletin No. /, Health Department, City of New York, 1895.

2 CcntralbLf. Bakt. u. JParasitenk., Bd. xxi., No. 3, Jan, 30, 1897.