72 BACTERIOLOGICAL EXAMINATION OF WATER. 



is a diffuse growth with a marked deposit, and in old cultures 

 the formation of a slight pellicle is seen. Nitrates are 

 vigorously reduced. 



I have frequently found in water an organism which closely 

 resembled the above. Milk, however, was not coagulated by 

 my cultures. 



B. Umbilicatus. 



This organism was frequently isolated from Chemnitz water 

 by Zimmermann. It is a short bacillus with rounded ends, 

 occurring singly and in pairs ; at times it forms long chains. It 

 has a rotatory movement and does not form spores. Gram's 

 method causes decolorisation of the bacillus. The optimum 

 temperature varies between 18 C. and 30 C. In plate cultures, 

 under a low power, the colonies at first appear as yellow points, 

 which enlarge and become granular. On the surface the colonies 

 show a wart-like appearance, but later they grow out and have 

 an irregular margin. To the naked eye the colonies appear at 

 first as greyish-white drops, which soon acquire an umbilicated 

 centre. In stab-gelatine on the surface there is a thin 

 irregularly-lobed growth ; along the line of inoculation there is 

 a good growth, often accompanied by the development of gas 

 bubbles. On agar there is a thin greyish-white growth with an 

 irregular margin. On potato there is a thin, smooth, yellowish- 

 grey growth. Broth becomes opalescent, and a white sediment 

 forms at the bottom of the tube. 



GROUP IX. 



This group includes a number of organisms which produce a 

 brown colour in nutrient media. 



B. Brunneus. 



Isolated by Adametz from water. It is a small, thin, non- 

 motile bacillus which forms spores. The colonies in gelatine 

 appear on the surface as small, dirty white drops. The under- 

 part of the colonies is at first white, then grey, and finally 

 brown in colour ; the gelatine is not liquefied. In gelatine-stab 

 it forms a slimy growth on the surface, which later becomes 



