BACTERIA FOUND IN MILK 213 



Vibrio Lissalbon. Obtained in a widespread cholera epidemic in 

 Lisbon, in which only one death occurred. On gelatine plates it forms 

 circular, sharply limited, slightly liquefying, whitish-yellow colonies. 

 Nitroso-indol reaction negative. 



Vibrio Phosphorescens (Dunbar). Isolated from the river Elbe. 

 Morphologically and in cultures it resembles the vibrio of Asiatic cholera, 

 but is distinguished by being phosphorescent. 



Vibrio Massauah. This vibrio possesses two to four flagella, while 

 the vibrio of Asiatic cholera has only one. The nitroso-indol reaction is 

 positive. It is pathogenic for pigeons, guinea-pigs, and rabbits. 



BACTERIA FOUND IN MILK. 



Bacteria are always present in milk unless it is drawn from the 

 udder under sterile precautions. Milk can be contaminated in various 

 ways : from the gland direct, i.e., B. tuberculosis, etc. ; c by the 

 hands of the milker, 1 dirty vessels, hay dust, etc., and by the water 

 added by the thrifty dairyman. Milk is an excellent medium for the 

 development of many forms of bacteria, and under favourable condi- 

 tions, temperature, etc., it quickly undergoes changes. 



Pathogenic bacteria may also contaminate milk. The organism 

 most frequently found being the B. tuberculosis. Pyogenic cocci have 

 also been found. From contamination with diseased matter from 

 affected persons and premises, milk may be the means of carrying and 

 spreading typhoid fever and diphtheria (and according to some 

 authorities, scarlet fever). Such organisms are, however, easily 

 destroyed ; the most resistant of all, the B. tuberculosis, being killed 

 by Pasteurizing the milk for thirty minutes at 70 C., or by cooking 

 the milk for ten minutes, whereby it is heated between 90 and 95 C. 

 Nothing now remains after the process of sterilization except the 

 resistant spores of some bacteria. (For special methods of examining 

 and staining bacteria in milk, see Technique, 20.) 



A. COCCI. 

 MICROCOCCUS ACIDI LACTICI. 



Found in fresh milk, occurring either as single large cocci or 

 diplococci. 



Biological Characters. Aerobic. 



On Gelatine Plates. Forms small yellowish non-liquefying colonies. 

 Milk is first coloured red, then coagulated, finally becoming de- 

 colorized. 



