Bacteria in Market Milk. 



The bacteria do not grow well in milk but they are found in 

 cheese, in the oriental varieties of sour milk and in sour food. 

 These bacteria are of only slight importance in the ordinary lac- 

 tic acid fermentation. They prefer higher temperatures and pro- 

 duce fermentation only in the absence of oxygen, although their 

 growth is prolific even in the presence of oxygen. 



As representatives of this group the Bacillus panis fermentati 

 occurring on sour bread should be mentioned, and the Bacillus 

 delbrucki found on sour food. 



Some representatives of these "cheese bacteria" are capable 

 at high temperature (40-50 cleg. C.) of producing and withstanding 

 large quantities of lactic acid, up to 1.5%, and even to 2 to 2.5%. 



Lohnis classifies the staphylococci as the fourth most widely 

 distributed bacterial group of the lactic acid producers, but on ac- 

 count of their peptonizing characteristics they might better be 

 considered with the casease bacteria of Weigmann. Their proper- 

 ties have already been described during the discussion of bacteria 

 of the first decomposing phase. The staphylococci may also be 

 separated into : 



(a) Those coagulating milk and liquefying gelatin. 



(b) Those which only liquefy gelatin. 



(c) Those which only coagulate milk. 



(d) Those which posses neither of these properties, 



nor form slime, produce gas, nor form tendrils. 



The species mentioned by no means exhaust the number of species and groups 

 which are capable of producing lactic acid. Thus the anthrax bacillus splits up sugar 

 and starch into lactic acid, and also forms acetic acid (Napias), and formic acid 

 (Iwanoff). Feinberg demonstrated for the diphtheria bacillus the capability of splitting 

 up milk sugar with the formation of alcohol, aldehyde and volatile as well as non-volatile 

 acids. The bacillus of malignant edema, according to Kerry and Frankel, in the 

 anaerobic fermentation of grape sugar, produces ethyl alcohol, formic acid, butyric acid 

 and lactic acid ; cholera vibrios and related organisms form lactic acid ; for instance 

 the vibrio of Asiatic cholera, the Vibrio proteus (Finkler and Prior), Vibrio ma-ssauah, 

 vibrio danubicvs and others form levo-rotary lactic acid, the vibrio of Deneke forms 

 dextro-rotary and Vibrio berolinensis produces an inactive lactic acid. The formation of 

 these lactic acids, however, does not depend on the bacillus alone. 



The Oidium lactis, a milk mould, and others, are also capable 

 of producing lactic acid from milk sugar. Some of the lactic acid 

 forming varieties are rare in milk, others may accustom themselves 

 to milk so rapidly that they form the typical acidifying flora, the 

 presence of which under certain conditions may be desirable since 

 by their multiplication the vegetation of the harmful peptonizing 

 bacteria and of the producers of butyric acid is inhibited. 



With this we leave the most important varieties of bacteria 

 which are responsible for the normal spoiling of milk, and will 

 briefly discuss those varieties of microbes belonging to the bacte- 

 riology of milk and milk production which always occur in market 

 milk. 



Milk also invariably contains butyric acid bacilli. Their pre- 

 dominance is inhibited by the lactic acid fermentation. 



