PROGRESS OF MICROSCOPICAL SCIENCE. 
31 
gelatinous scum seen floating on the top of water containing putrescent 
organic matter, and this he named " zoogloea." He then described 
the Bacterium termo in these words : * " Cellulse minimaB bacilli- 
formes, hyalinae gelatina hyalina in massas mucosas globosas, uv89- 
formes, mox membranaceas consociataB, dein singulae elapsse, per aquam 
vacillantes; " and he considered them as of decidedly a vegetable 
nature, and as allied to the Oscillatoriaceae. In a more recent pam- 
phlet he placed them amongst the family PhycochromaceaG, in a 
natural order named SchizosporeeB. His last investigations have led 
him to divide Bacteria into four groups and six genera, as follow : — f 
I. Spheero-bacteria. Genus 1 . Micrococcus char, emend. 
II. Micro-bacteria. Genus 2. Bacterium char, emend. 
III. Desmo-bacteria. Genus 3. Bacillus n. g. 
Genus 4. Vibrio char, emend. 
IV. Spiro-bacteria. Genus 5. Spirillum, Ehr. 
Genus 6. Spirochssta, Ehr. 
Of these genera the Bacterium, Vibrio, Spirillum, and Spiroch^eta were 
in the original Vibrionia family of Ehrenberg. 
Cohn considers the ferment of contagion to be due to the presence 
of a variety of the Sphasro-bacteria, the micrococci of Hallier. The 
whole group he divides into three : the chromogen, zymogen, and 
pathogen — the micrococci of pigmentation, of ferment, and contagion 
respectively. These organisms are exceedingly minute, darkish, or 
coloured granules, so small as to be immeasurable. They frequently 
present the appearance of beaded chains, or the form of aggregations 
(colonies). They are motionless, and are occasionally found with the 
Bacterium termo in putrefying organic liquids. Among the pathogen 
micrococci I may mention the M. vaccince, observed by Cbauveau and 
Sanderson in the vaccine lymph ; the M. dij)lithericus, which is pro- 
bably the same organism as that described by Professor Eberth, of 
Zurich, as attacking first the epithelial elements of a part, and subse- 
quently the deeper tissues, and which led him to say " the metastatic 
pyaemia is for the most part a diphtheria with numerous localizations ;"J 
and, lastly, the M. se^ticus.^ found, according to Cohn, in the miliary 
eruption of typhus, pyaemia, and other diseases. The chromogen, or 
pigmentary micrococci, have occasionally been the means of working 
miracles. Several instances of bread exuding blood, under superna- 
tural circumstances, are related by Rivolta.|| Ehrenberg found this 
colour on some bread in the house of a patient who had died of cho- 
lera, and he ascertained the pigment to be due to the presence of the 
Monas lorodigiosa — small roundish bodies, which Cohn classes with 
the micrococci. 
The true bacteria Cohn divides into two species, the B. termo and 
B. lineola. The B, termo are small dumb-bell-shaped organisms, 
* Nova Acta,' xxiv., p. 123- 
I Cohn, ' Betrage zur Biologie der Pflanzen,' Breslau, 1872. 
J Ebei-th, ' Zur Kentniss d. Bacterit'schen Mykosen,' Leipsig, 1872, p. 15. 
^ The Microsporon septicum of Klebs 
j| 'Del Para itti Vegetali,' Turin, 1873. 
VOL. xm. D 
