112 BACTERIA AND THE DISINTEGRATION OF CEMENT, 



carbonate capable of permitting the growth of bacteria are few 

 in number, Reinschf in experimenting with the Elbe water 

 below Hamburg found that 2 % permitted the growth of some 

 unidentified water bacteria, while 3 % did not. Fermi | has 

 recorded the action of potassium hydrate upon many micro- 

 orf'anisms. Excluding the micrococci, which appear to be less 

 influenced by the presence of this alkali in culture-media than 

 rod-shaped bacteria, the organism that can withstand most 

 potassium hydrate is Bad. luteum, a yellow bacterium which has 

 some affinities with Bad. croceum. The growth of Bad. hiteum 

 is inhibited when 1 2 drops ( = 0-6 c.c.) of normal potassium hydrate 

 have been added to 5 c.c. of nutrient agar. This is equal to 0*67 % 

 of potassium hydrate. Experiments with Bad. croceum showed 

 that growth occurred in the presence of 1*6 % potassium hydrate, 

 but no growth took place when double that amount was used. 



The presence in the cement of an organism capable of growing 

 with so much alkali is noteworthy. It is also significant that the 

 same organism was found at depths of four and six inches in one 

 place, but also at a depth of four inches into the disintegrating 

 cement face in another portion of the canal below Prospect 

 Reservoir, some miles distant from Kenny Hill, from where the 

 first samples were obtained. The indifference of the organism to 

 the alkali does not warrant the assumption that it is the cause of 

 the disintegration, but there is the possibility that it may have 

 something to do with it. To obtain some knowledge concerning 

 its action, an experiment was made with cement blocks. These 

 consisted of equal volumes of sand and old cement, and also of 

 two volumes of sand to one of new cement. When they had 

 hardened and had been sterilised, a culture of Bad, croceum was 

 painted on the surface of the blocks with a platinum loop and 

 the infected blocks were placed on a glass shelf in a desiccator 

 which was filled up to the level of the blocks with boiled and 

 cooled tap water. The whole vessel had been sterilised, and 



t Reinsch, Centralblatt ftir Bakt. i. Abt., x. 415. 

 J Fermi, ibid, xxiii, 208. 



