534 NOTE ON THE BACTERIOTOXIC ACTION OF WATER, 



persistent. He found that, after a water had supported the 

 multiplication of a particular species of micro-organism, the 

 latter, on being reintroduced into the same water, will not only 

 not again multiply, but, in many cases, will actually suffer rapid 

 destruction. He compared this immunity of the water to the 

 generation by the bacteria of soluble and toxic products, which 

 inhibit their further growth and multiplication. These soluble 

 products can be concentrated by evaporation at a low tempera- 

 ture, but are destroyed by boilino;. 



The effect of boiling is noteworthy, for while Martin says that 

 typhoid bacteria soon perish in sterilised {i.e., boiled) water, 

 Meade Bolton found that water-bacteria increase enormously 

 when introduced into sterilised water kept at 22''. That this 

 depends upon the individual species of bacteria, has been shown 

 by Rosenberg, who introduced a series of water-organisms into 

 sterilised distilled water, and found that, while the majority of 

 the individual varieties multiplied quickly, three of the species 

 rapidly died out. 



Having shown that bacteriotoxins can be demonstrated in 

 soils, that they are produced there and are leached out by rain, 

 it appeared to me to be a natural corollary tliat they should be 

 found in drainage- waters. Furthermore, they ought to occur in 

 natural waters in which bacteria are growing, although the 

 quantity will, in all probability, be small and somewhat pro- 

 portional to the number of bacteria which are present. In pur- 

 suance of the idea underlying my work upon the bacteriotoxins 

 of soils, a few experiments were made with Sydney tap-water. 

 This is an unfiltered water; the only purification to which it is 

 subjected, consists of being strained through a series of sieves of 

 a fine mesh at the city-reservoirs. It contains few bacteria; for 

 example, on September 22nd, 1913, the date of the first experi- 

 ment, at a temperature of 16°, it was found to contain 140 bac- 

 teria per c.c. when seeded into Lipman's synthetic agar. 



The experimental method consisted in filtering the water 

 through porcelain filters (Chamberland F) and adding one c.c. of 

 a suspension of £ac. prodigiosus to 10 c.c. of the water, unboiled 

 and after having been boiled for 15 and 60 minutes under a 



