VAUIUTIKS OF BACILLUS PYOCYANEUS 121 



carried on according to old-fashioned rules and without any knowledge of the 

 internal reactions occurring therein. One thing is certain : these reductions are 

 not purely chemical operations, but are true fermentations, as already emphasised 

 by A. Frrz (IV.) in 1878. Frequently they proceed in an undesired direction ; 

 two such maladies of the indigo bath being : destruction of the colour, and 

 blackening. However, as regards these, mycological investigations are still 

 lacking. 



S 97. Varieties of Bacillus Pyocyaneus. 



The number of bacterial species capable of producing blue colouring matters 

 is by no means exhausted by those mentioned in the three preceding paragraphs. 

 A fourth, which has been repeatedly referred to in earlier chapters, is the Bacillus 

 pyocyaneus^ described by C. GESSARD (II.). This organism, conveyed in atmo- 

 spheric dust, comes in contact with the pus exuded from wounds, and developing 

 therein, produces, as its name implies a coloration ranging from blue to verdigris 

 green. This microbe, which really belongs to pathological and not to technical 

 mycology, is very mutable a property which must also be briefly dealt with here. 

 In addition to the blue pigment designated pyocyanine which may be separated 

 from the cultures byshaking them up with chloroform, and which was first prepared 

 in the pure crystalline state by FORDOS (I). the parasite in question, when 

 cultivated in bouillon, produces a green fluorescent colouring matter. By skil- 

 fully modifying the conditions of nutrition GESSARD (III. and IV.) obtained three 

 varieties, morphologically indistinguishable, one of them producing only pyocya- 

 nine, the other only the fluorescent pigment, and the third no colouring matter 

 at all. Whilst these 'three varieties can be re-transformed into the typical 

 species, such change cannot be effected with a fourth variety, cultivated by 

 CHARRIN and PHISALIX (I.), which had permanently lost its chromogenic faculty. 

 Unaware of this variability, P. ERNST (III.) proposed to distinguish between two 

 species Bacillus pyocyaneus a arid /3, a course which Gessard considers incorrect. 

 In contradiction to the results obtained by the latter worker, and confirmed by 

 HANS BUCIINER and ROHRER (I.), K. THUMM (I.) asserted that B. pyocyaneus 

 produces only a single pigment, the blue. Undoubtedly this investigator, as a 

 result of the system of cultivation preferred by him, unwittingly deprived the 

 bacillus of its property of elaborating the green fluorescent colouring matter. 



During the past two decades there has been isolated from water, air, and soil a 

 number of blue-producing species of Schizomycetes, which, however, are of no 

 special importance, and can therefore merely be mentioned here, though fully 

 described in Eisen berg's work. They are : Bacillus janthinus, obtained by Zopf 

 from the river Panke, Berlin ; Bacillus berolinensis indicus, by H. CLAESSEN (I.) 

 from the Spree ; Bacillus lividics, by Plagge from Berlin town-water ; Bacillus 

 cceruleus, by ALLEN J. SMITH (I.) from the water of the Schuylkill river. It is 

 probable that these species are chromoparous, as was established with certainty 

 in the cxi.se of a fission fungus obtained by Voges from natural water in Hol&tein 

 (and also named Bacillus cceruleus), which excretes the blue colouring-matter 

 into the surrounding medium, where it collects into small granules. 



At the present time a fairly large number of species producing violet 

 pigments are known ; they are found in the same places as the above-named, and 

 are equally of little practical importance. A few may be cited as examples, the 

 oldest species known being the Bacteridium violaceum, observed by Schroeter, 

 and named Micrococcus violaceus by Cohn. This organism develops on solid 

 media (gelatin, potatoes, &c.) to solid-growing violet-blue colonies. In contrast 

 to this is Bacillus violaceus, which liquefies gelatin and produces a deep violet colour. 

 Bacillus membranaceus amethystinus was discovered by Jolles in Spalato well- 

 water, and produces a dark violet pigment exhibiting a metallic lustre. 



