LIPOCHROMKS 107 



become alkaline from the tranbformation products (trimethylamine, &c.) excreted 

 by the microbe. 



In addition to the form of the cells, the development of colouring matter is, 

 as Schottelius has found, also dependent on the nutritive conditions; since, if a 

 prodigiosus culture, grown at io-25 0. and already red in colour, be inoculated 

 on sterile potatoes (steamed and cut in halves), and the temperature kept at 

 38-39 0., the inoculating streaks develop into colourless streak cultures. 

 From these again a red culture can be once more obtained by suitably modifying 

 the conditions of the culture, i.e. reverting to a lower temperature. 



88. Lipoehromes. 



With the organism mentioned in the last paragraph are classified a number 

 of other species also producing red colouring matter. One of these, Bacillus 

 erythrosporus, first discovered by ED. EIDAM (I.) in putrefying egg albumen, is of 

 particular interest. This is a slender motile bacillus, which does not liquefy 

 gelatin. As is indicated by its second name, the seat of the dirty red colouring 

 matter is not in the vegetative form of growth, but in the endospores. The 

 so-called (motile) " Kiel bacillus" found by Breuning in the Bay of Kiel, occurs 

 generally as long rods (0.8 p broad, by 2.5-5 P- l n g)> which liquefy gelatin. 

 There is great similarity in the red colouring matter produced by this bacillus 

 and Micrococcus pi'odigiosus, but the former microbe is distinguished by its 

 greater susceptibility to direct sunlight, which, according to the researches of 

 E. LAURENT (I.) permanently destroys its chromogenic power. A similar 

 effect is produced by the presence of carbohydrates in the medium, the -Kiel 

 bacillus, in such event, elaborating no colouring matter. The following chromo- 

 parous red species will only be briefly alluded to : Bacillus ruber, discovered by 

 Frank and described by COHN (II.) ; Bacillus indicus, discovered in the contents 

 of the stomach of an East Indian ape ; the Bacillus granulatus of Babes ; 

 Bacillus corallinus, isolated by C. SLATER (I.) from atmospheric dust, and the 

 Bacillus rubellus, discovered by OK AD A (I.), which forms endospores and thereby 

 assumes the clostridium form. 



Greater interest attaches to several red and yellow species studied by ZOPF 

 (IV.), and especially as regards their colouring matters, which were named by 

 him lipochromes or fat-colouring matters. These are excreted from the cells 

 and collect between them to form dendritic crystalline aggregations, which are 

 luminous in the darkened field of the polariscope. The lipochromes known at 

 present are red and yellow, the former being styled liporhodine and the latter 

 lipoxanthine. The reagent for these is concentrated sulphuric acid, whereby 

 they are converted into deep blue acicular crystals of lipocyanine, which remain 

 isolated when derived from lipoxanthine, but arrange themselves in characteristic 

 groups when produced from liporhodine. Illustrations of these will be found in 

 OVERBECK'S (I.) work on this subject. These colouring matters can be extracted 

 from the cultures by means of ethyl alcohol, in which they are just as soluble as 

 in methyl alcohol, chloroform, carbon bisulphide, and benzene. On evaporating 

 the solvent, a fatty mass, furnishing the acrolein reaction, remains behind. This 

 being saponified and salted out with a hot solution of sodium chloride, the liquid 

 underlying the soapy layer will contain the colouring matter, which can then be 

 extracted by shaking up with petroleum spirit and examined spectroscopically. 

 Of these species the following were more closely examined by ZOPF (V.) : Micro- 

 coccus rhodochrous, isolated from the contents of a goose's stomach, is about 0.9 p. 

 in diameter, and will grow on nutrient gelatin, potato discs, <fcc., to form deep 

 red masses. The absorption spectrum of the liporhodine extracted therefrom 

 shows an absorption band in F. The Micrococcus erythromyxa, obtained from 



