AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 505 



Gelatin stab. In gelatin, growth is slow and a very slow fun- 

 nel-like liquefaction is produced. 



Gelatin colonies. They appear coarsely granular, slightly 

 raised mth definite yellow-brown centers. The centers are 

 coarsely flocculent under the low power of the microscope. The 

 colonies are surrounded by a slight area of liquefaction. 



Broth. A slight turbidity is produced and a definite scum is 

 formed which settles to the bottom. 



Peptone. Growth similar to that in broth. 



Potato. A fairly profuse grayish-white moist growth. When 

 the medium is dry the growth is scale-like. 



Litmus milk. No change is noticed within 24 hours. After 

 48 hours a slowly progressive peptonization occurs. The med- 

 ium becomes amber-colored. 



Blood serum. A fine-grained leather-like growth occurs, dull 

 gray and adherent to the medium. Later this is easily scraped 

 off. No solution of the serum occurs. 



Fermentation tubes. Glucose : a flocculent growth occurs in the 

 bowl and extends into the closed arm. Reaction acid. 



Saccharose: turbidity in bowl. Arm clear. Reaction neu- 

 tral or slightly acid. 



Lactose : turbidity in bowl. Arm clear. Reaction not changed. 



Thermal death point. The spores resist 18 pounds pressure in 

 the autoclave but are destroyed by 20 pounds. They survive 

 one hour's steaming in the Arnold. 



SPORE-BEARING ORGANISMS IN WATER 



BY C. A. LAUBACH 



The spore-bearing organisms in water were obtained by pass- 

 ing the tap water in the laboratory through Berkefeld filters 

 under pressure for a period of three days, washing the filters in 

 sterile salt solution, heating the washings to 80°C. for 15 min- 

 utes and then plating. Ten samples were obtained by this 

 method and 313 organisms studied. The species previously es- 

 tabUshed from studies of milk and dust were found as follows: 



