io8 CHROMOPAROUS BACTERIA 



the town- water of Halle, has a diameter of 1.0-1.2 /*, and its colonies on the 

 nutrient media referred to resemble in appearance those of the first-named 

 species. In addition to liporhodine, however, it produces a yellow colouring 

 matter, soluble in water, but of unknown nature. 



Antithetical to these two red- producing species are : Bacterium egregium, 

 obtained from atmospheric dust ; then Bacterium chrysogloia ; and finally the 

 Staphylococcus pyogenes aureus, already several times referred to in the previous 

 chapter. The.se three develop into yellow cultures producing lipoxanthine, the 

 absorption spectrum of which consists of two bands, one near F and the other 

 between F and G. 



89.-Red Coloration in Milk 



may be due to various causes, one of them being an admixture of blood derived 

 from a broken blood-vessel in the udder. In this case the coloration of the 

 liquid is not uniform, but is due to scattered patches of red, fiocculent blood 

 coagulum. If, on the other hand, the milk is found to be uniformly coloured 

 red or reddish throughout the entire mass as soon as it is drawn from the udder, 

 then other causes are in operation. If the colour undergoes no change on stand- 

 ing, it is attributable to the fodder having contained a large quantity of madder 

 (Rubia tinctoruiii) or of Galium verum. Should, however, the red-drawn milk 

 precipitate a red sediment on standing, the colour of the liquid concurrently 

 decreasing, then the coloration is due to a transudation of haematin. This case 

 is analogous to that of " red water," and is a consequence of the consumption of 

 highly stimulating fodder. 



When, however, a normal milk gradually becomes red after standing, then 

 micro-organisms are at work ( Micrococcus prodigiosus being frequently the agent), 

 and the colouring matter excreted by the organism is absorbed by the fat 

 globules of the milk. This microbe has already been more minutely characterised 

 in the preceding paragraph. 



A second milk-reddening organism is the Bacillus lactis erythrogenes, dis- 

 covered by Hueppe and more closely examined by GROTENFELT (I.). The non- 

 motile rods of this organism are 0.3-0.5 p. in diameter, with, usually, a length of 

 1-1.5 M) but attaining to 4.3 fj. in bouillon. This fission fungus (which liquefies 

 gelatin) grows on solid media to yellow colonies, which excrete around their 

 periphery a red colouring matter. When inoculated into sterile milk it pro- 

 duces a gradual coagulation attended with a sickly-sweet odour, without affecting 

 the reaction of the liquid to any appreciable extent. The serum gradually clari- 

 fying from the deposited casein absorbs the resulting deep red colouring matter, 

 which develops most copiously in the dark and ceases to form if the culture be 

 exposed to light or the medium has an acid reaction. Its absorption spectrum 

 exhibits two strong bands between the lines D and E and a third in the blue. 

 A species of fission fungus allied to B. lactis erythrogenes has been isolated from 

 red milk by A. BAGINSKV (I.). 



Of the sarcina group two species are known to be endowed with the faculty 

 of reddening milk. One of these was discovered by K. MENGE (II.), viz., 

 Sarcina rosea Menge ; and the second was isolated from red milk by L. ADAMETZ 

 (II.), and was identified with the Sarcina rosea Schroeter, very frequently met 

 with in the air. Apart from the red coloration, Menge's sarcina produces 

 no noteworthy changes in milk, but Schroeter's sarcina, on the other hand, first 

 precipitates the casein which is subsequently gradually re- dissolved. Conse- 

 quently a milk-culture (growing dark brown in colour) kept at 25 C. for four 

 to five weeks no longer exhibits any deposit beyond a sediment consisting of 

 sarcina packets. 



Red coloration in cheese may arise from various causes, those of a purely 



