34^ BACTERIA. 



occurring in the water of the Tweed, contain a cblouring 

 matter which has been described as resembling in a most 

 remarkable manner the aniline dyes ; in fact, in the case of 

 the pigment of the magenta micrococcus, the resemblance is 

 carried so far that in old cultures even the peculiar metallic 

 lustre of the aniline dyes is reproduced. Other pigments 

 are soluble in water, but not in, alcohol, whilst the bacterio- 

 purpurin formed by Eteggiatda 'Roseopersicina is like chloro- 

 phyll, insoluble in both alcohol and water. The name 

 bacterio-purpurin, howeVer, has been given By 'fingelmann 

 to the pigment produced or possesseji by a whole group of 

 yrgafiisrris. He concludes that it has, in thfesS' itiwer grganiStiis', 

 the function of the chlorophyll of the higher plants.. If 

 exposed on the microscope ;stagE. to the light of a sub-stage 

 spectroscope apparatus, these bacterio-purpurin .bacteria 

 invariably tend ,tQ. collect 013. that part of the slide that is 

 over the ultra-red baiids &f the spectrtiiny'the .portion | of. the 

 spectrum 'where the absorption of light by :the', bacterio- 

 jputpurin 'occurred. He found that the analog with -plarijl^ 

 and -chldfophyll becariie 'still closer, from , the fact ijiai 

 wherever this * occurred, oxygen 'was' set - free, .arid'- ,th£ft 

 light in fact' was riec6ssdfy for , the continued, ejdstbticfe. 

 of .these bacteria arid for the- devdopment of,' theit 

 charac'teristic •' colour - producing power. In the casS . '8f 

 this ' otganisnij acc6rding to Ray Lankester, th^ colo'ur 'fs 

 actually contained' within the protoplasm of tiie orgahistri, 

 where it appears in some cases to be'combined ■with sulphur, 

 to forril dark granules.- In some cases the colour," in'place of 

 remaining within the organism, "becomes diffused iicito'thfe 

 surrounding media. As^ an example of this may Tdc cited 

 theliacillus of " blue milk," which, growing along thp track 

 of the needle in a gelatine cultme, sends . o,uf- a , peculiar 

 iridescent green coloration into the surrounding gelatitie' ; 

 as time goes' on this-' gl'een' is, replaced by a smoky, brown 

 colour. Similarly the Bacillus fiubrescens putidus -iniparfe 

 to the gelatine,, or '^any other material on which' it is grow- 

 ing, a peculiar fluorescent greeny and at the same time gives 

 off an odour of herririg brine. ;' ' 



That ithe decomppsitipn. of the sulphates in the presence of iron and 

 organic matter plays a most important part in the production of these pig- 

 ments has now been, fully recognized. If it "be borne in mind that sulphi^js 

 of the various metals appear as beautiful precipitates when thrown down from 



