2 E. KLEIN. 
first twenty-four to forty-eight hours the colonies are made up 
entirely of cylindrical bacilli, some of extreme length and 
forming very characteristic threads. The “swarming” out and 
the development of strands from such a colony are uniformly 
due to, and consist of, thread-like bacilli (see my article in 
Stevenson and Murphy’s ‘Treatise on Hygiene,’ II, pl. 11); 
but later on, say after three or four days, when liquefaction of 
the gelatine has become extensive, the forms one meets are 
those various kinds described by Hauser as coccus forms, ovals, 
cylindrical cells, and vibrionic forms. 
(5) The Bacillus filamentosus (which I found in sewage, 
and which I described in my article in Stevenson and Mur- 
phy’s ‘ Treatise on Hygiene,’ II, fig. 14) is, under all conditions 
of culture (gelatine, agar, broth, serum, &c.), always made up 
of cylindrical cells, either singly or in pairs, or forming longer 
and shorter chains. 
The same applies to the Bacillus subtilis, the bacillus of 
swine erysipelas, and the bacillus of human typhoid fever. 
(c) The Bacillus prodigiosus, on the other hand, remains 
under artificial cultivation in the various media pre-eminently 
of the spherical or slightly oval shape, while there are always 
present a few cylindrical forms, and it is owing to the greatly 
prevalent number of coccus forms that in former years this 
organism was described (Cohn, Schrotter) as the Micrococcus 
prodigiosus, 
Another interesting point connected with the unstable shape 
under which some species appear is that while some, growing 
in one medium, appear under one particular shape, this changes 
when growing in a different medium. A group of bacteria are 
known, the essential biological character of which is that most 
of them produce acute septiceemic infection in one or the other 
rodent. To this group belong the bacillus of fowl cholera, 
of fowl enteritis, of Frettchenseuche, of Wildseuche, of swine 
fever, of the Middlesborough pneumonia, of grouse disease, the 
Bacillus coli, and others. 
Now all these in their cultural characters in the different 
media have many points in common, as also the close resem- 
