200 BACTERIA IN MILK AND MILK PRODUCTS 



tion bacteria. The Bacillus lactis pituitosi, a slightly curved, non- 

 liquefying rod, which is said to produce a characteristic odour, in 

 addition to causing ropiness, brings about some acidity. B. lactis 

 mscosus of Adametz, B. actinobacter of Duclaux, B. Hessii of Guille- 

 beau, and other bacilli are similar agents. Many of the above 

 organisms, with others, produce " slimy " fermentation in alcoholic 

 beverages as well as in milk. 



(c) So&py--llfttk~is another form of fermentation, the etiology of 

 which has been elucidated by Weigmann. The Bacillus lactis 

 saponacei imparts to milk a peculiar soapy flavour. Ij^was de.frectgd^ 

 in the straw of the bedding and hay of the fodder, and from such 

 sources may infect the milk. There is little or no coagulation, 

 but a certain amount of sliminess and ropiness, with a peculiar 

 soapy taste to the milk. 



(d) Chromogenie Changes^ We have already remarked that 

 colour is the^natural and apparently chief product of many of the 

 innocent bacteria. They put out their strength, so to speak, in the 

 production of bright colours. The chief colours produced by germs 

 in milk are as follows : 



Red Milk. Bacillus prodigiosus, in the presence of oxygen, causes 

 a redness, particularly on the surface of milk. It was possibly the 

 work of this bacillus that caused " the bleeding host " which was one 

 of the superstitions of the Middle Ages. B> lactis erythrogenes pro- 

 duces a red colour only in the dark, and in milk that is nut strongly 

 acid in reaction. When grown in the light this organism produces a 

 yellow colour. There is a red sarcina (Sarcina rosca) which also 

 has the faculty of producing red pigment. One of the yeasts is 

 another example. It must not be forgotten that redness in milk 

 may actually be due to the presence of blood from the udder of the 

 cow. 



It is of importance clearly to differentiate between milk reddened 

 by the admixture of blood from the mammary gland, and that pro- 

 duced by the organism isolated and studied by Hueppe and Groten- 

 feldt Bacillus lactis erythrogenes the presence of which in the 

 milk is now looked upon as the active causation of the disease. In 

 the former case the coloration is apparent immediately after milking, 

 is uniform, and if the milk is allowed to rest the flocculent blood 

 coagulum causing the coloration will gradually sink and deposit 

 itself in the form of a precipitate at the bottom of the milk 

 receptacle. In the latter the red spots do not appear until later, the 

 infection of the milk is comparatively slow, and the milk serum is 

 alone affected, the cream layer not taking the red coloration. 

 This is probably due to the simple fact that the cream layer being 

 at the surface is exposed to the light, which inhibits the coloration. 

 A general coagulation of the milk takes place accompanied by a 



