BY R. GREIG SMITH. 749 



water, bub they showed that during the times that the Lawrence 

 city filters were undergoing repair, the mortality from typhoid 

 fever rose, and this occurred simultaneously with a rise in the 

 numbers of Bad. coli commune in the water. When this 

 organism could no longer be found in 1 c.c. of the water the 

 epidemic ceased. 



Of the microbes found in various waters some are pathogenic, 

 others are not. In the Thames River water, Marshall Ward* 

 separated a number of organisms which were more or less patho- 

 genic to guinea-pigs. The most strongly pathogenic forms were 

 those that resembled B. coli commune so closely as to suggest to 

 that author that they had been derived at some time from that 

 organism and had been modified in their cultural characters, etc., 

 by environment, i.e., by their having been immersed in water for 

 a more or less prolonged time. More recently, Weissenfeldf has 

 shown that varieties of coli can be obtained from many waters 

 that are undoubtedly pure, and that these varieties are more or 

 less pathogenic when inoculated into the tissues of guinea-pigs. 

 From this it would appear that the reaction of a bacterium when 

 innoculated into animals is no criterion as to the purity of the 

 water containing the organism, that is to say, that the patho- 

 genicity of the coli-like and other forms tells us nothing about 

 the value of the water for dietetic purposes. 



The usual method employed for getting the micro-organisms 

 which are suspended in a large quantity of water into a smaller 

 ami workable volume consists in filtering 2, 3 or 5 litres through 

 a porcelain filter, and in brushing the organisms from the surface 

 of the filter into a small quantity, say 10 c.c. of sterile water. 

 Aliquot portions of the 10 c.c. represent parts of the original 

 quantity taken. An alternative method has been recommended 

 by Zikes | The bacteria are entangled in a precipitate of 

 aluminium hydrate, formed by the addition of sterilised solutions 



* Marshall Ward, Proc. Royal Society, No. 376, p. 417 (1897). 

 t Weissenl'eld, Zeitschrift fur Hygiene, xxxv., 78. 

 X Zikes, Jour. Soc. Chem. Industry, xix., 364, Abs. 



