GREEN BACTERIA. 159 



Bacillus fluorescens non-liquefaciens which grows on the same 

 medium into solid colonies. Both organisms occur in natural 

 waters. The author in 1891 discovered a fission fungus of very 

 frequent occurrence in Munich butter, and named it Bacillus 

 butyri fluorescens. 



C. GESSARD (V.) recorded a beautiful observation in connection 

 with the formation of fluorescent pigment by Bacillus pyocyaneus. 

 This substance is in the case of nutrient solutions prepared arti- 

 ficially from mineral salts produced only when phosphates are 

 present in quantity equivalent to at least 0.25 grm. of potassium 

 phosphate per litre. When this supply is reduced, the organism 

 develops, but produces no fluorescence. This behaviour is also 

 exhibited by other fluorescent bacteria, so that these can therefore 

 be regarded as very delicate tests for potassium phosphate. 



K. THUMM (I.) comparatively examined a number of bacterial 

 species yielding fluorescent cultures, viz., Bacillus fluorescens tennis, 

 B. fl. putidus, B. fl. albus, B. erythrosporus, B. viridans, B. pyo- 

 cyaneus, Bacterium si/ncyaneum (Bacillus syncyaneus). These 

 species produce, in alkaline gelatin, a fluorescence initially sky- 

 blue, but afterwards moss-green, caused by an excreted yellow 

 pigment, which is formed only when the medium contains mag- 

 nesium sulphate and potassium phosphate. 



The green coloration of cheese is, as first determined by CARLO 

 BESANA (I. ), due to the presence of copper, this evil being especi- 

 ally manifested by Lodisan cheese, the Parmesan cheese produced 

 in Lombardy formaggio di grana lombardo. The initially yellow 

 cut surface of this cheese becomes green by exposure to the air. 

 For the successful preparation of this cheese a certain fairly high 

 degree of acidity in the milk equal, according to J. RAVA (I.), to 

 0.22 per cent, of lactic acid is essential, and therefore it is the 

 custom in Lombardy to leave the milk to acidify in untinned 

 copper vessels, whereby it takes up a considerable quantity of 

 copper. In fact, the progress of the souring is determined by the 

 gradual disappearance of the metallic lustre from the previously 

 polished surface of the vessels. G. MARIANI (I.), who examined 

 twenty-five samples of these cheeses for their content of copper, 

 found the minimum to be 54 m.grms. of Cu per kilogrm. of cheese, 

 and the maximum 215 m.grms., the average per kilo, of Lodisan 

 cheese being 100-1 10 m.grms. of copper. That this metal alone is 

 actually responsible for the green coloration of cheese is evidenced 

 not only by comparative laboratory experiments with tinned and 

 untinned milk vessels, but also by the fact that the Parmesan 

 cheeses made south of the river Po (especially in Reggio), and 

 brought to Parma for sale, undergo no alteration in their yellow 

 colour when cut. In that region, however, the milk is left to 

 acidify in wooden tubs. 



