12 



THE AMERICAN MONTHLY 



[January, 



to know, in its lesser details the 

 premature classification of M. Cohn ; 

 it suffices to refer to certain 2^enera 

 respectively the cellules and the rods 

 which are most frequently found. 

 Among these are the micrococci, 

 bacteria, leptothrix and vibriones. 

 To avoid all misunderstanding, we 

 briefly describe these genera, and 

 name the varieties that are there 

 most frequently found. 



Micrococcus^ Hallier.— This name 

 is given to a number of minute 

 spherical or oval cellules, motionless, 

 isolated or in couples, sometimes 

 serially disposed like a string of 

 beads. The colored micrococci or 

 Chromogenes, studied by Professor 

 Cohn, possess no special physiolog- 

 ical interest, while those studied by 

 M. Pasteur are, in this connection, 

 quite remarkable ; of these may be 

 cited the M. urea^ the acetic ferment 

 {Mycoderma aceti), and the viscous 

 ferment. According to Hallier, 

 the pathological micrococci are 

 quite numerous; however, up to 

 this time their existence is regarded 

 as hypothetical by the most author- 

 itative savants, De Bary, Hoffman, 

 and Cohn himself, who, neverthe- 

 less, admits the existence of the 

 micrococci of vaccine, of diptheria 

 and of septicemia. 



Bacterium, Dujardin. — This 

 genus is restricted to motile forms 

 of cells, longer than broad, isolated 

 or united in twos, fours, and rarely 

 in larger numbers. The true bac- 

 teria differ from the bacilli by their 

 short articulations, and from micro- 

 cocci by their movement. These 

 characters are, indeed, of little help 

 to the microscopist who is called 

 upon to determine the genus of a 

 microbe by a simple examination. 

 Often, in fact, at low temperatures 

 and in media poor in oxygen and 

 plastic materials, the bacilli greatly 

 resemble bacteria. Schroter has 

 described some chromogene bac- 



teria, Ehrenberg the Bacterium 

 termo and pttnctum, Dujardin the 

 B. catenula, finally Warming three 

 or four other varieties. 



Bacillus, Cohn, — Among the 

 species placed in this group are all 

 the motile or motionless organisms 

 in the form of rigid rods, long and 

 short, large and small, disj^osed in 

 chains oi one, two, three or more 

 articles ; one is naturally led to 

 place in this category all bacteria of 

 considerable length. 



Among the more remarkable 

 bacilli should be cited Bacillus 

 anthracis^ discovered by Dr. Da- 

 vaine, and which was recently the 

 object of researches by MM. Pas- 

 teur and Joubert ; the butyric fer- 

 ment of Pasteur, one of the most 

 singular of the rod-like forms ; the 

 lactic bacillum, and some others of 

 wine and silk-worm maladies. 



The Bacillus amylobacter, 

 studied by MM. Trecul and Yan 

 Tieghem, which has been classed as 

 a distinct species, according to the 

 recent work of Yan Tieghem, is 

 merely the butyric ferment ; from 

 which it results that the same or- 

 ganism possesses the power of trans- 

 forming calcic lactate into the 

 butyrate (Pasteur), of causing fer- 

 mentation of cellulose (Yan Tieg- 

 hem), and of a large number of 

 other substances, with a disengage- 

 ment of hydrogen. If one adds 

 to these facts, that the butyric fer- 

 ment of Pasteur lives and develops 

 in the absence of the oxygen of 

 the air, one will understand the 

 importance attached to a perfect 

 knowledge of many fermentations, 

 of which this organism may be 

 the primal cause. Dr. Davaine 

 has described several bacilli of pu- 

 trefaction, the physiological func- 

 tions of which are less perfectly 

 known. 



Finally, Cohn has given the name 

 Bacillus subtilis to a rod-like or- 



