162 Bacteria in Market Milk 



Oidium lactis participates principally in the sixth phase of decom- 

 position, although other varieties of moulds, penicillia, and mucors 

 may also play a part. The degree of acidity being diminished by 

 the oidium, bacteria of the fifth phase again commence to multiply, 

 until the seventh phase is inaugurated through the growth of the 

 anaerobic butyric acid bacilli. According to Koning this phase is 

 reached at room temperature on about the eighth day. 



Grasberger and Schattenfroh designate ; the principal representative of this 

 bacterial group, the Bacillus saccharobutyricus immobilis llquefaciens, a bacillus which 

 is large, thick and stubby, stains after Gram, and forms spores which are located either 

 centrally or at the end of the bacillus. According to Burri the bacillus may be most 

 readily isolated by boiling the milk for several minutes, and allowing it to ferment at 

 37 deg. C. Besides this butyric acid ba-cillus, other motile forms or bacteria related 

 to the first group may be found. 



The seventh phase finally passes into the eighth, in which the 

 milk changes into a stinking putrid fluid, in which the decomposi- 

 tion of the food material is completed by the proteus, subtilis, 

 Bacillus fluorescens, and Bacillus mesentericus, besides mould 

 fungi. 



Of these phases of decomposition of milk the first three, espe- 

 cially the second and possibly the beginning of the third phase, are 

 the most important. 



In these two phases the proteolytes and the rennet formers 

 are the first to multiply, causing a partly visible precipitation of the 

 casein, but subsequently again dissolving it; further, the precipi- 

 tated protein is immediately partly dissolved when the dissolving 

 tryptic ferment is present to excess. Weigmann collects these 

 bacteria under the name of casease bacteria. On account of their 

 properties of producing peptones from proteid bodies they are 

 called peptonizing- bacteria. Most of them liquefy gelatin/ The 

 group of casease bacteria includes a great number of forms of 

 bacteria, for instance : 



Staphylococci, small spherical bacteria which occur ubiquitously and in smears 

 from cultures appear as grape-like conglomerates. They stain by Gram 's method. They 

 grow from deg. to about 40 deg. C., and frequently form at 15 to 20 deg. and over, 

 yellowish orange, or lemon-yellow colored colonies. At a low temperature the casease 

 enzymes are especially active. In gelatin stab cultures Staphylococci first develop a 

 nail-like growth; the liquefied gelatin may then dry and at the point of the stab a 

 bell-shaped air vesicle forms, or the liquefaction may progress rapidly and a cloudy 

 layer of liquid with a sediment of Staphylococci stands above the solid gelatin. 



In gelatin plates the small round colony drops into a cup-shaped depression which 

 also results from the drying of the liquefied gelatin. Besides the formation of albumose 

 and peptones the milk sugar is split up ; Lohnis therefore classifies these organisms with 

 the lactic acid bacteria. 



The growth of sarcina, which collect into two, four or eight members, etc., is 

 similar, thereby forming bacterial clumps of certain forms. They are also Gram-positive. 



On account of their occurrence even in milk drawn in the most cleanly manner, their 

 presence in the udder was accepted, and as a matter of fact pathogenic organisms do 

 occur in the group of Staphylococci, which produce inflammations of the udder. Ordinarily 

 however, they only inhabit the milk duct. 



The putrefactive representatives of the proteus varieties should be classified 

 among the non-spore bearing casease bacteria. They manifest many forms of growth, 

 and include the following representatives: Proteus sopfii, zerikeri, vulgaris, mirabilis, 

 and fluorescens. 



