408 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
bacilli are soon exterminated by tbe lactic acid ferment. The bacilli 
were cultivated in 10 per cent, gelatin to which 1/2 per cent, pepton 
was added. The colonies were circular and surrounded by a zone of 
black pigment in which lime crystals were deposited. The bacilli 
are strongly aerobic, and liquefy gelatin. The individual rodlets are 
of variable size, from 0 - 2 to 0 - 6 p, long, and about half as thick. 
When alive they are mobile and colourless, when dead they become 
brown. 
The chief characteristic of this organism is the formation of pig- 
ment, the colour of which varies with the stage of development. When 
cultivated in 1/2 per cent, pepton solution the hue is first green, then 
blue, brown, and black, after this the solution loses its colour almost 
altogether. 
On solid media the pigment is seen as blue or black areas of an 
irregularly spheroidal shape. Of course the formation of pigment is 
the most interesting characteristic of the micro-organism, and it serves 
as text for the author to discuss at some length chromogenic bacteria 
in general, and to propose a subdivision of them into chromophorous, 
chromoparous, and parachromophorous. In the chromophorous the 
pigment is an integral part of the cell-element and is comparable to 
the haemoglobin in a red corpuscle. The chromoparous bacteria 
are, when alive, at first always colourless, the pigment being excreted 
as such or as a colourless chromogen. 
In the parachromophorous bacteria the pigment, although obviously 
an excretion, adheres to the bacterial body as in the chromophorous 
bacteria. 
As this organism was found to thrive at 20° C. if kept at this 
temperature for a short time only, but underwent some loss of vitality 
so that it was unable to be bred on solid media, although capable of 
being still cultivated in liquids, it is suggested that the virulence of 
many bacteria, e. g. those of cholera, erysipelas, and the like, might be 
retained successfully if they were cultivated in media not too strong in 
nutritive properties and at temperatures as low as possible, but suited 
of course to each organism. 
Bactericidal Property of Rat’s Blood.* — Behring having stated that 
the inhibitory effect of rat’s serum on anthrax stood in causative relation 
to the immunity of rats to anthrax, MM. Metschnikoff and Roux per- 
formed a series of experiments in order to controvert the proposition. 
The results of the experiments certainly seem to indicate that rat serum 
possesses a powerful bactericidal property, yet the authors conclude that 
the bactericidal power of rat serum, very manifest “ in vitro,” does not 
explain the relative immunity of some of these animals to charbon. 
The preventive action that this serum exerts when it is injected in mice 
at the same time as the charbon virus is not due to an immunization of 
the mice, but to the direct influence of the serum on the bacteria, and 
also to its chimiotactic power on the leucocytes. In this case, as well as 
in all others studied by the authors, phagocytic phenomena play an 
important part. 
* Annal. de l’lnst. Pasteur, 1891, pp. 479-86. See Centralbl. f. Bakteriol. u. 
ParaBitenk., x. (1891) pp. 756-8. 
