ABNORMAL BUTTER AND CHEESE. 115 



the technical literature. Hueppe found a Bact. lactis eryihro- 

 genes in red milk, which is described by Grotenfelt as a short 

 rod coagulating milk, and producing a red colour on gelatine 

 plates. Menge found a Sarcina rosea in red milk, which also 

 forms red colonies on gelatine, and a few other species with 

 similar properties have been detected. In yellow milk a 

 Bact. synxanthum has been observed and described by 

 Schroter. 



The taints observed in butter must also be chiefly attri- 

 buted to micro-organisms, and in the technical literature it 

 is strongly emphasised that a great development of such 

 harmful species is frequently caused by a want of cleanliness, 

 or by a wrong souring of the milk. The rancidity of butter, 

 which is due to the presence of butyric acid and ethyl butyrate, 

 is caused by the action of light and air. According to 0. 

 Jensen this phenomenon is due to the presence of aerobic 

 fungi, which cause the decomposition of fat, in particular 

 Cladosporium butyri and Oidium lactis. This may further be 

 due to the presence of two bacteria universally found in water, 

 Bac. fluorescens liquefaciens and, occasionally, Bact. prodigiosum. 

 The action of light may also produce the tallowy taste, but 

 Storch has isolated a rod-shaped, lactic acid bacterium which 

 can produce the same effect. A turnip flavour and a rotten- 

 sweet flavour in butter, studied by C. 0. Jensen, proved to 

 be derived from a special species, Bacillus joetidus lactis. 

 Weigmann has subsequently observed similar bacteria. A 

 whole series of other irregularities in the character of butter 

 are also accompanied by the growth of different micro-organ- 

 isms, and the assumption is reasonable that they must be the 

 originators of these taints. 



One of the most pronounced faults with cheese is " blowing/' 

 which is due to the presence of great masses of fermentation 

 bacteria causing an excessive development of gas ; in particular, 

 a species, Bac. Schafferi, belonging to the Bac. coli group, plays 

 an important part in this respect. The same fault may be 

 produced in cheese by the species originating from diseased 

 udders. Yeasts may produce a strong evolution of gas and 

 certain varieties of coli and aerogenes species may also bring 

 about vigorous fermentation with production of gas. A 



