40 DAIRY BACTERIOLOGY 



as Bacterium pneumonice, and some bacteria which, according to 

 Gillebeau, cause inflammation of the udder. The second type, to 

 which belongs Bacterium lactis aerogenes, produces less slime, and 

 its colonies on gelatine are often but little larger than those of the 

 lactic acid streptococci. They generally coagulate milk by the 

 production of succinic acid and Isevo lactic acid. The aerogenes 

 bacteria can convert the citric acid of the milk into acetic and 

 carbonic acids. On corn and flour aerogenes bacteria are found 

 which produce a yellow colouring matter. Bacterium cloacce is a 

 liquefying aerogenes bacterium. Motile forms related to this 

 organism may be regarded as a link w r ith the Proteus bacteria. 

 In cheese such forms are often found, but these form spores in one 



end of the cell, and must there- 

 fore be designated as aerobic 

 Plectridia. 



The coli bacteria are as a 

 rule peritrich, though often 

 they are only slightly motile. 

 They differ from the aerogenes 

 bacteria in producing about 

 equal quantities of carbon 

 dioxide and hydrogen, and also 

 ^ n their P ower to decompose 

 casein. In the latter respect 

 they show a certain resem- 

 blance to the true lactic acid 

 FIG. 45. The Coli Bacterium which spoilt bacteria, but they carry the 



the Milk and Butter at Duelund Dairy . . 



in 1888. (After c. o. Jensen.) x 1,000. decomposition further than the 



ammo acid stage, producing 



evil-smelling bodies, a circumstance which links them with the 

 putrefactive" bacteria. The kind of lactic acid formed by the 

 coli bacteria is influenced to some extent by the particular 

 sugar fermented, and also by the nature of the nitrogenous 

 nutrient matter present. They commonly form large amounts 

 of succinic and acetic acids. Their surface colonies may re- 

 semble those of the aerogenes bacteria in exceptional cases, but 

 as a general rule, they spread out in thin, skinny layers. Numerous 

 species of coli bacteria are known, many being pathogenic, giving 

 rise to intestinal and other diseases such as typhoid fever and 

 dysentery. Bacterium typhosum (Fig. 27) distinguishes itself by 

 being very actively motile, while the dysentery bacteria are non- 

 motile. None of these form gas. The commonest cases of meat 

 poisoning are also due to certain coli bacteria, Bacterium enteriditis. 

 The very dangerous coli bacteria which are dealt with here can 

 easily be distinguished from the ordinary coli bacteria by the fact 



