TEXT-BOOK OF BACTERIOLOGY. 189 



solves itself into a number of the most different forms. A simple 

 experiment will suffice to illustrate this, superficially at least. 

 Take a drop of any putrefying liquid, put it into gelatin, and spread 

 it over a glass plate; it will always be found that quite a number 

 of different colonies appear, which, of course, must be carefully ex- 

 amined as to their appearance and behavior. 



Moreover, the process of putrefaction is attributed, by a very 

 high authority, chiefly to the action of strictly anaerobic bac- 

 teria, while the micro-organism described as Bacterium termo was 

 certainly not anaerobic. 



Bacterium termo is for us, therefore, an abstract idea, and does 

 not apply to any one species. It should be banished from our no- 

 menclature until some well-defined species is found that performs a 

 particularly important and conspicuous part in the process of pu- 

 trefaction, and to which we might then justly give the name 

 " Bacterium termo " as a title of honor. 



To arrive at such a result extensive investigations would be 

 necessary, for hitherto the important question of putrefaction has 

 remained an almost unploughed field of bacteriological research. 



Hauser, it is true, had described, under the name of proteus, 

 some species in which he believed he had discovered important ex- 

 citers of decomposition in organic substances containing albumin. 

 But the results which he has made known are not yet so fully 

 established as to be regarded in the light of indisputable fact. 



Of the three species described by him, the one which he calls 

 Proteus vulgaris is interesting to us on account of the peculiar for- 

 mation of its colonies. 



It is a small, slightly-curved rod-cell, very mobile, which often 

 occurs in pairs, seldom in long chains. It has a remarkable tend- 

 ency to deviate from its normal form, and sometimes produces 

 cells like those of the cocci, sometimes twisted threads which have 

 hardly a trace of resemblance to the original shape a phenomenon 

 which justifies the denomination "proteus." 



On the glass plate an extensive liquefaction of the gelatin soon 

 appears, and with this remarkable disposition of the colonies: they 

 lie as yellowish-brown, bristly heaps in the centre of the liquefied 

 portion and appear to have bunches of hair along their margin. 

 The liquefaction of the gelatin spreads over the medium in such 

 curious intricate twistings and arabesques, and often produces such 

 peculiar figures and patterns, that this micro-organism has been 

 called the figure-forming bacillus. These intricate markings are 

 pale and colorless, and look as if cut or scratched into the gelatin. 

 They are caused by the dissolving power of the bacterial cells. If 



