62 BACTERIA. 



but it is difficult to associate the characters that he gave with any of the red 

 pigment forming organisms now known. 



Felix Dujardin added very little to the actual classifications given by 

 Miiller and Ehrenberg, but he brought out several most important facts. 

 In certain large vibrios he was able to make out distinct bifurcation, the 

 two new limbs becoming segmented transversely ; he was also able to 

 recognize an outer membrane or resistant covering on these organisms, and 

 within this a gelatinous or protoplasmic material. This led him to doubt 

 whether, after all, he was dealing with an animal form, and several of the 

 forms described he relegated to the plant kingdom as Algse — Vibrio subtilis 

 of the Oscillaria. 



As Loffler points out, although Dujardin was not able 

 to make any further advances on the classifications of Miiller 

 and Ehrenberg, his observations on the chemistry of bacteria 

 were most important. He describes as specially suitable for 

 the development of bacteria, fluids containing such substances 

 as phosphate of soda, hyponitrous acid and oxalate of am- 

 monia and carbonate of soda, and he points out that the 

 nitrogen from the oxalate of ammonia is gradually used up 

 in the presence of organic substances. 



With the exception of Dujardin, as we have seen, all observers up to 

 1852 had looked upon bacteria as belonging to the animal kingdom, but 

 in this year Perty announced that of these minute organisms, some 

 belong to the animal and some to the vegetable kingdom, whilst a 

 certain number appeared to him to stand on the borderland between the 

 two. These vibnones, he says, are colourless or sometimes blue, yellow, 

 or reddish, never green, organisms, with scarcely a trace of any differentia- 

 tion of their substance ; they have a spontaneous or automatic movement ; 

 they increase in number by transverse division, partial or complete ; when 

 this is incomplete, chains or threads are formed. He divides them into 

 Spirilla or spiral threads. Bacteria or winding or straight threads, and he 

 thinks that the bacteria have not only an active animal life, but that they 

 also pass through a stage during which they must be looked upon as vege- 

 table in character : a double existence which he assigned to other forms. 



In 1854 Cohn insisted even more strongly on the plant 

 nature of these micro-organisms. He, too, described zoogloea 

 masses, and he summed up his researches as follows : — (i) 

 All vibriones seem to belong to the vegetable kingdom, and 

 they exhibit a very close relationship to the larger algse. (2) 

 In respect of their want of chlorophyll, and ol their occurrence 

 in putrefying infusions, the vibriones belong to the group of 

 water fungi (mycophyceae). (3) Bacterium termo is the 

 active, moving form of a closely-related species of palmella 

 and tetraspora zoogloea. (4) Spirochaete plicatilis belongs 

 to the species spirulina, which we can at once indicate as a 



