Sc i e n t i f i c Me mo i r s b y
of certain species, tends to induce this result quite apart from the influence
of any other conditions. In this instance, however, conditions of temperature
also unequivocally came into play in determining the result, as was con
- c l u s i v e l y p r o v e d b y t h e f a c t t h a t w h e r e , r e s p e c t i v e l y , t h e m e m b e r s o f p a i r e d
sub-cultures were exposed to a temperature of 37°C, and to ordinary atmos
- p h e r i c t e m p e r a t u r e s r a n g i n g f r o m 6 2° t o 6 6°F . , t h e f o r m e r g a v e t h e r e a c t i o n
at periods when the latter entirely failed to do so. In both cases alike—in that
of continued cultivation on media of like nature, and in that of exposure to rela
-tively elevated temperatures—the determinant of the earlier appearance of the
reaction was probably alike, and lay in increased activity of growth, owing in the
first case to progressive acclimatization to a particular environment, and in the
second to elevation of temperature.
A series of tube-cultures was established, which, maintained by successive
transfers during a period of many months' duration, yielded growths retaining a
uniform character throughout. The superficial growth in stab-cultures occurred
rapidly, and ultimately became of considerable thickness ; interstitial growth also
was present along the entire course of the track of the needle, at first present
- i n g i t s e l f i n t h e f o r m o f a v e r y d e n s e c o l u m n a r o u n d t h e t r a c k a n d s u b s e q u e n t l y
becoming diffused throughout the rest of the medium. The constituent
elements of the growths throughout the entire series of cultures remained alike,
and presented the form of relatively short, thick, well-curved commas. Broth
cultures gave pale purple throughout, within 24 hours, on adding pure sulphuric
acid. It is not, however, the question of the presence of specific peculiarities,
but the phenomena of commensalism as affecting capacity for growth under
certain conditions with which we have to deal in the present instance, and the
above particulars are merely given in order to show that the organism may fairly
claim the right of being regarded as a characteristic choleraic vibrio.
The influence of commensalism came out in connection with potato-cultures
for, in cases in which the basis was devoid of any contamination, no growth of
commas whatever occurred, whilst where any development of a large form of
bacillus, apparently closely allied to the common potato-bacillus, took place, it
was invariably accompanied by extensive multiplication and diffusion of commas
over the entire surface of the substratum. The characters of the commensal
growths and of those of pure growths of the host-bacillus were practically alike.
In both cases they assumed the form of a rapidly developed, thin thallus, soon
spreading over the entire surface of the substratum, primarily very moist, cover
-ed with vesicular blebs and showing numerous bright yellow points variegating
the pale ochre of the rest of the surface. Somewhat later the thallus dried up
and presented itself as a closely wrinkled membrane, primarily of a bright
canary yellow and later of a warm buff tint. The smell was very powerful,
sweet, fruity and agreeable.
The microscopical characters of the growth, where commensal, varies at