510 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
the softened portion having a funnel-shaped appearance. "When 
grown in glycerin-agar the bacilli presented a fairly constant form, 
mobile rodlets 1-3 /x long being the predominant variety, while on 
gelatin they were inconstant in appearance, varying from spheroidal 
forms to filaments 12 to 20 /x long, although 2 to 3 /x was the most 
frequent length. 
Inoculation experiments with pure cultivations of this bacillus showed 
that it was pathogenic to cold and warm-blooded animals, such as frog, 
toad, salamander, lizard, eel, guinea-pig, rabbit, dog, cat, mice, bat, 
hedgehog, pigeon, and fowl. 
From the rapid action of the injections on animals, the author sup- 
posed that the metabolic products of these bacilli were endowed with 
some specially toxic properties, yet he admits that the intravenous and 
subcutaneous injections of fluid obtained by filtering broth and gelatin 
cultivations through a Chamberland’s filter failed to bear out his assump- 
tion. The author next notices the points of difference between this 
bacillus (JB. hydrophilus fuscus ) and that described by Ernst, B. rani - 
cida , a form connected with an epidemic disorder to which frogs are 
liable in spring. 
Variability of the Red Bacillus of Kiel Water.* — M. Laurent suc- 
ceeded in depriving the Kiel water bacillus of its red pigment by exposing 
it to the action of sunlight, and the alteration thus induced was found to 
be constant, lasting for generations. This pigment is soluble in water 
and alcohol, less so in benzin, and insoluble in chloroform and sulphuric 
acid. In the presence of small quantities of acid the red pigment 
assumes a brighter hue, while alkalies have the contrary effect. The 
bacillus thrives between 10° and 42°, but the optimum temperature is 
from 30° to 35°. If air be excluded development may proceed, but 
without the formation of pigment. 
Acid reaction of the medium (1 per thousand free tartaric acid) 
prevents development, the bacillus itself, in the presence of sugar, forming 
no inconsiderable quantity of acid, which eventually stops its growth. 
Before this has taken place the production of pigment has ceased, 
although a very feeble acid reaction seems to impart a more lively hue to 
the pigment. The temperature and the presence of carbonic acid have 
some determining influence on the shade of the pigment. 
To light the bacillus is extremely sensitive ; exposure for three hours 
to sunlight falling vertically caused the large majority of the colonies to be 
quite colourless, a condition which was retained by successive generations. 
Exposure for one hour had only a transitory effect, while five hours 
killed the colonies. Control experiments made with cultivations from 
which air was excluded, or in atmospheres of hydrogen or carbonic acid, 
showed that the alterative effect of the sun’s rays was only evinced in 
co-operation with air. 
Differences in the action of the component rays of the spectrum were 
not made out. 
The colourless generations obtained by exposure to light retained 
their condition up to the thirty-second transference on potato at from 
* Annales de l’lnstitut Pasteur, 1890, p. 465. See Centralbl. f. Bakteriol. 
u. Parasitenk., ix. (1891) pp. 105-6. 
