222 A MANUAL OF BACTERIOLOGY 



appears that this acidity is necessary for this typical 

 growth, for on potatoes rendered slightly alkaline 

 there appears a yellowish or dirty grey growth with 

 sharply-defined margins a growth quite different 

 from that above described.' 



Fraerikel and Simmonds 1 state that this microbe 

 is the cause of typhoid fever, for they have pro- 

 duced the disease in monkeys, mice, and rabbits, by 

 inoculation, from a pure cultivation of the microbe. 

 Many other microbes (especially micrococci 2 ) 

 'appear in the intestines when the disease is ap- 

 proaching its end, but the bacillus in question is the 

 only one found in the blood and internal organs [as 

 well as in the roseolous eruption], so that it is really 

 characteristic of the disease.' 



According to Janowski, 3 the action of light is 

 detrimental to the growth of B. typhosus; and he 

 has also proved that a temperature of 55C., con- 

 tinued for ten minutes, destroyed the microbe. 

 Although destroyed at 55 C., B. typhosus has been 

 found alive in ice which had remained continuously 

 frozen for a period of 103 days; 4 and Dornil has 

 discovered that ice is often a medium for transmit- 

 ting infectious diseases especially typhoid fever. 

 But if ice is a means of transmitting typhoid fever, 

 potable water is a much more dangerous source of 

 infection. ' The remarkable instance which occurred 

 at the Caterham Waterworks (1879), where by the 



1 Die Aetioloyische Bedeutung des Typhus-bacillus, 1886. 



2 Klein, Reports of Medical Officer of the Privy Council, 1875. 



3 Centralblattfur BaJcteriologie, Bel. 8 (1890). 



4 F. Davis's Handbook on Potable Water (1891). 



