An important conference upon cholera was held in Berlin, at the
Imperial Board of Health, on the evening of July 26. There were present
Drs. Von Bergman, Coler, Eulenberg, B. Frankel, Gaffky, Hirsch, Koch,
Leyden, S. Neumann, Pistor, Schubert, Skrezcka, Struck, Virchow, and
Wollfhugel. The conference had been called at the instance of the
Berlin Medical Society, whose President, Professor Virchow, explained
that it was thought advisable Dr. Koch should in the first instance
give a demonstration of his work before a smaller body than the whole
Society, so that the proceedings might be fully reported in the medical
press. He mentioned that Herr Director Lucanus and President Sydow
had expressed their regret at being unable to be present, as well as
many others, including Drs. Von Lauer, Von Frerichs, Mehlhausen, and
Kersandt. Dr. Koch first showed various specimens of the bacilli and
their method of preparation (see _Berliner Klinische Wochenschrift_,
August 4). This resembles that for the tubercle bacillus, viz.,
drying on a cover glass and staining with fuchsin or methyl-olin.
Koch then gave a history of his work while in Egypt and India. His
post-mortem examinations led him to believe that the intestines were
the nidus of the disease. At first his microscopical examinations were
unsatisfactory, but finally he got fresh dejecta and acute cases, and
then discovered the comma bacillus.
This, he said, is smaller than the tubercle bacillus, being only about
half or at most two-thirds the size of the latter, but much more plump,
thicker, and slightly curved. As a rule, the curve is no more than that
of a comma (,), but sometimes it assumes a semicircular shape, and he
has seen it forming a double curve like an S; these two variations from
the normal being suggestive of the junction of two individual bacilli.
In cultures there always appears a remarkably free development of
comma-shaped bacilli.
These bacilli often grow out to form long threads, not in the manner
of anthrax bacilli, nor with a simple undulating form, but assuming
the shape of delicate long spirals--a corkscrew shape--reminding one
very forcibly of the spirochæte of relapsing fever. Indeed, it would be
difficult to distinguish the two if placed side by side. On account of
this developmental change, he doubted if the cholera organism should
be ranked with bacilli; it is rather a transitional form between the
bacillus and the spirillum. Possibly it is true spirillum, portions
of which appear in the comma shape, much as in other spirilla, _e.
g._, spirilla undula, which do not always form complete spirals, but
consist only of more or less curved rods. The comma bacilli thrive
well in meat infusion, growing in it with great rapidity. By examining
microscopically a drop of this broth culture the bacilli are seen in
active movement, swarming at the margins of the drop, interspersed with
the spiral threads, which are also apparently mobile. They grow also
in other fluids, _e. g._, very abundantly in milk, without coagulating
it or changing its appearance. Also in blood serum they grow very
richly. Another good nutrient medium is gelatine, wherein the comma
bacilli form colonies of a perfectly characteristic kind, different
from those of any other form of bacteria. The colony when very young
appears as a pale and small spot, not completely spherical as other
bacterial colonies in gelatine are wont to be, but with a more or less
irregular, protruding, or jagged contour. It also very soon takes on
a somewhat granular appearance. As the colony increases the granular
character becomes more marked, until it seems to be made up of highly
refractile granules, like a mass of particles of glass. In its further
growth the gelatine is liquefied in the vicinity of the colony, which
at the same time sinks down deeper into the gelatine mass, and makes a
small thread-like excavation in the gelatine, in the center of which
the colony appears as a small white point. This again is peculiar;
it is never seen, at least so marked, with any other bacterium. And
a similar appearance is produced when gelatine is inoculated with a
pure culture of this bacillus, the gelatine liquefying at the seat of
inoculation, and the small colony continually enlarging; but above it
there occurs the excavated spot, like a bubble of air floating over
the bacillary colony. It gives the impression that the bacillus growth
not only liquefies the gelatine, but causes a rapid evaporation of the
fluid so formed. Many bacteria also have the power of so liquefying
gelatine with which they are inoculated, but never do they produce such
an excavation with the bladder like cavity on the surface. Another
peculiarity was the slowness with which the gelatine liquefied, and
the narrow limits of this liquefaction in the case of a gelatine disk.
Cultures of the comma bacillus were also made in agar-agar jelly, which
is not liquefied by them. On potato these bacilli grow like those of
glanders, forming a grayish-brown layer on the surface. The comma
bacilli thrive best at temperatures between 30° and 40° C., but they
are not very sensitive to low temperatures, their growth not being
prevented until 17° or 16° C. is reached. In this respect they agree
with anthrax bacilli. Koch made an experiment to ascertain whether
a very low temperature not merely checked development, but killed
them, and subjected the comma bacilli to a temperature of -10° C.
They were then completely frozen, but yet retained vitality, growing
in gelatine afterward. Other experiments, by excluding air from the
gelatine cultures, or placing them under an exhausted bell-jar, or in
an atmosphere of carbonic acid, went to prove that they required air
and oxygen for their growth; but the deprivation did not kill them,
since on removing them from these conditions they again began to grow.
The growth of these bacilli is exceptionally rapid, quickly attaining
its height, and after a brief stationary period as quickly terminating.
The dying bacilli lose their shape, sometimes appearing shriveled,
sometimes swollen, and then staining very slightly or not at all. The
special features of their vegetation are best seen when substances
which also contain other forms of bacteria are taken, _e. g._, the
intestinal contents or choleraic evacuations mixed with moistened earth
or linen and kept damp.
A most important statement was that the comma bacillus seems to be
killed by the bacteria of putrefaction, and consequently agents that
destroy the latter organisms without the former may really do injury,
by removing from the cholera bacillus an impediment to its growth.
As for destructive agents to the bacillus, he found it killed by
solutions in the following proportions: oil of peppermint, 1 in 2,000;
sulphate of copper, 1 in 2,500 (a remedy much employed, but how much
would really be needed merely to hinder the growth of the bacilli in
the intestine!); quinine, 1 in 5,000; and sublimate, 1 in 100,000.
In contrast with the foregoing measure for preventing the growth of
these bacilli is the striking fact that they are readily killed by
drying. This fact is proved by merely drying a small drop of material
containing the bacilli on a cover glass, and then placing this over
some of the fluid on a glass slide. With anthrax bacilli vitality is
retained for nearly a week; whereas, the comma bacillus appears to be
killed in a very short time.
Dr. Koch having found and cultivated the comma bacillus and ascertained
its distinctive character, next proceeded to investigate its relation
to cholera. In all there were now about one hundred cases of cholera
in which the bacillus had been found, while it was never found in
connection with other diseases. Three different views, said the
speaker, as to its relation to the cholera process are tenable:
1. That the disease favors the growth of these bacilli by affording
them a suitable soil. If so, it would mean that the bacillus in
question is most widely diffused, since it has been found in such
different regions as Egypt, India, and France; whereas the contrary is
the case, for the bacilli do not occur in other diseases, nor in the
healthy, nor apart from human beings in localities most favorable to
bacterial life. They only appear with the cholera.
2. It might be said that cholera produces conditions leading to a
change in form and properties of the numerous intestinal bacteria,
a pure hypothesis; the only instance of such a conversion refers to
a change of physiological and pathogenic action, and not of form.
Anthrax bacilli under certain conditions lose their pathogenic power,
but undergo no change in shape; and that is an instance of a loss of
pathogenic properties, while there is no analogy to support the view of
the harmless intestinal bacteria becoming the deadly cholera bacilli.
The more bacterial morphology is studied, the more certain it is that
bacteria are constant in their form; moreover, the comma bacillus
retains its special characters unchanged through many generations of
culture.
3. Lastly, there is the view that the cholera process and the comma
bacilli are intimately related, and there is no other conceivable
relation but that the bacilli precede the disease and excite it. "For
my own part," said Dr. Koch, "the matter is proved that the comma
bacilli are the cause of cholera."
Dr. Koch then described his attempts to inoculate lower animals with
the bacillus, and explained the cause of his failure in the natural
immunity of the animals against the disease.
In advocating the local Indian origin of the disease he said: That the
virus can be reproduced and multiplied outside the body is apparent,
since the bacillus can be cultivated artificially, and its growth is
not affected by comparatively low temperatures. Probably it does not
grow in streams and rivers, where, owing to the current, a sufficient
concentration of nutrient substance does not occur; but in stagnant
water and at the mouths of drains, etc., vegetable and animal refuse
may accumulate and afford the necessary nutriment. Thus is explained
the propagation of cholera by the subsoil water, and the increase of
epidemics with the sinking of its level, which lessens the flow and
diminishes the amount of surface water. Admitting the dependence of
cholera upon this micro-organism it is impossible to conceive the
disease having an autochthonous origin in any particular place; for a
bacillus must obey the laws of vegetable life, and have an antecedent;
and since the comma bacillus does not belong to the widely diffused
micro-organisms, it must have a limited habitat. Therefore, the
occurrence of cholera on the delta of the Nile does not depend on its
resemblance to the delta of the Ganges; but the disease must have
been imported there as it is into Europe. It was once thought that an
outbreak in Poland had a local origin until it was discovered to have
been introduced from Russia. Again, about ten years ago, there was a
sudden outbreak at Hamar (Syria), thought to be an instance of local
origin, but erroneously, as shown by a statement of Lortet, who told
Koch, when at Lyons, that the epidemic had been introduced into Hamar,
where he was at the time, by Turkish soldiers from Djeddah. All great
epidemics of cholera began in South Bengal, where the conditions for
the development and growth of the bacillus are most perfect.--_Med.
Record._