32 
PROGRESS OF MICROSCOPICAL SCIENCE. 
having a slowly vacillating motion, and about -g^Vo"" Tsiir^" 
length. I have elsewhere given Cohn's description of these micro- 
bacteria and their zoogloea. They are essentially the ferment of 
putrefaction, and it is doubtful whether putrefactive changes can take 
place without them. It is probable that Ehrenberg confounded this 
Bacterium with the Vibrio lineola in his plates in the work before 
noticed. The B. varicosum of some writers is possibly this species, 
although, when fresh names are introduced in classification without 
sufficient description, some doubt will always be cast upon the accu- 
racy of the investigation. 
The B. lineola is somewhat larger than the preceding species. It 
is endowed with stronger and more rapid to-and-fro movements. 
It is rod-shaped, and is essentially the ferment of sour milk. It is 
equivalent to the Vibrio lineola of Ehrenberg, the V. iremulans and 
B. triloculare of the same author, and to the V. lineola of Dujardin. 
The Desmo-bacteria, or " linked rods," are distinguished, as their 
name implies, from the true bacteria by being occasionally united 
together in chains. They are thus separated: the filament trans- 
versely lined — Bacillus ; the filament cylindrical and curved — Vibrio. 
The Bacilli Cohn divides into three species : 
The first, the B. subtilis, is the Vibrio subtilis of Ehrenberg. It is 
a slender supple thread found in stale boiled milk. Its length is 
about 5^^". It moves with a pausing motion, " like a fish forcing 
its way through reeds." 
The B. anihracis of Cohn is the Bacterium carbuncolare of some 
writers. It is described by Eivolta * (following Davaine and Delafond) 
as an immovable, oblong, highly refractive body, found in the blood 
of animals affected with the disease. Its size (according to Davaine) 
varies much, from Toio^o-" to 4-0V0" 2 (Too"' unaffected by 
water, alcohol, ether, acetic, nitric, or phosphoric acid, or soda, potass, 
or ammonia. Sulphuric acid readily destroys it. It is occasionally 
found united in chains of two or three links. 
Lastly, the Bacillus ulna is distinguished from the B. subtilis by 
the greater thickness of its filaments and by its rigidity. Its length 
is about -^i-Q-". Cohn found it in a stale infusion of boiled egg. 
The "Vibrios are distinguished from all the preceding genera by 
their rotary motion. This motion, which most writers had restricted 
to the Spiro-bacteria, Cohn, I think, rightly applies to the movements 
of the Vibrio. The V. rugula is generally seen with one or two slight 
curves in the form of the signs ) or $. A flexible thread, 25V0"" 
ttVtj"" long ; rotation slower than in the following species. This 
organism was found in the evacuations of cholera and diarrhoea by 
Leeuwenhoek, and by Davaine in the pus of balanitis also.j The 
second species, the V. serpens, is distinguished by the greater number 
and regularity of its curves, by the rigidity of the filament, and its 
more rapid rotation. The thread is also considerably thinner than 
the F. rugula, and its length is about 2oV(r"' The motion is ser- 
pentine in appearance. 
The Spirilla (including the Sjpirochce taplicatilis, for I do not 
♦ Rlvolta, op. ext., p. 47. t Davaine, ' Entozoakes,' 1860, p. 5. 
