912 ON THE EXAMINATION OP WATER FROM THE SYDNEY SUPPLY, 



it cannot furnish precise results, and, therefore, cannot be of 

 comparatively great value for the bacteriological analysis of water. 

 Number of Colonies of Bacteria. 

 In the following table I give a brief account of the number of 

 bacterial colonies which made their appearance on the cultivation- 

 plates, after a period of from two to three days' incubation, at a 

 temperature of about 20° C. (68° F.) They are always calculated, 

 in the now customary and conventional way for one cubic centi- 

 meter (1) of the samples under treatment. These figures have been 

 arrived at by a series of single experiments, made on 1 4 different 

 samples, within the space of about two months. This is indicated 

 by the date when the sample had been taken. Moreover, I noted 

 the temperature of the water operated upon, and besides the amount 

 of bacterial colonies in general, I thought it well not to omit to 

 state in a special column the number of those colonies which caused 

 liquefaction of the gelatine. It is especially bacteria of this kind 

 which induce fermentative and putrefactive processes in organic 

 substances, although there are, on the other hand, important 

 pathogenic species of bacteria, e.g., the bacillus of typhoid fever 

 (Eberth), which do not liquefy the nutrient gelatine in the least. 



(1) 1 cubic centim. (ccm.) ='060242 cub. inch. 



